ABSTRACTS SUBMITTED IN SESSION 4
Beam Dynamics and Electromagnetic Fields
915 - RHIC Vertical AC Dipole Commissioning*
M. Bai, J. Delong, P. Oddo, C.-I. Pai, S. Peggs, T. Roser,
T. Satogata, D. Trbojevic, A. Zaltsman, BNL, Upton,
Long Island, New York
The vertical RHIC ac dipole was installed in the summer
of 2001. The magnet is located in the interaction region
between sector 3 and sector 4 and common to both beams.
The resonant frequency of the ac dipole was first
configured to be around half of the beam revolution
frequency to act as a spin flipper. At the end of the RHIC
2002 run, the RHIC vertical ac dipole frequency was
reconfigured for beam dynamics studies.A 3~$\sigma$
vertical betatron oscillation was
excited with the vertical ac dipole, where $\sigma$ is the
rms vertical beam size. RHIC IPM (Ionization Profile
Monitor) measurements also confirm that the beam
transverse emittance is preserved after the vertical
excitation. The betatron functions and phase advances at
each BPM~(Beam Position Monitor) around the ring were
measured using the coherence excited by the vertical ac
dipole. We also used the excited coherence to measure the
2x2 coupling transfer matrix at each BPM location. Both
measurements for are presented in the paper along with
the analysis algorisms for each of these measurements.
The work was performed under the auspices of the US
Department of Energy
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1496 - Adiabatic Matching in Periodic Accelerating
Lattices for Superconducting Proton Linacs
G. Bellomo, P. Pierini, INFN LASA, Segrate (MI)
Superconducting proton Linacs with multicell cavities are
split in sections (using cavities with different geometrical
length) with a spatially periodic lattice (typically a
focusing doublet and 2-4 cavities in a lattice period) and
slowly varying focusing and acceleration parameters. The
usual matching procedure for a constant parameter lattice,
namely periodic conditions on the transverse and
longitudinal Twiss parameters gives poor results,
especially in the presence of strong space charge forces. A
novel matching procedure has been devised, valid for
adiabatic variations of the beamline and beam parameters.
This procedure gives smooth beam envelope variations
along the machine, as well as a smooth phase advance per
period. Examples will be given for the case of the
superconducting TRASCO Linac.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1849 - Recent Progress in Six-Dimensional Ionization
Cooling Techniques for Muon-Based Machines*
J.S. Berg, R. Palmer, BNL, Upton, Long Island, New York
Ionization cooling is an essential component of a neutrino
factory or a muon collider. Ionization cooling in the
transverse dimensions is reasonably straightforward, and
has been incorporated in published neutrino factory
studies. Achieving cooling in the longitudinal dimensions
is more difficult, but has the potential to greatly improve
the performance of neutrino factories, and is essential to
muon colliders. Much progress has recently been made in
describing ring cooling lattices which achieve cooling in
all three phase space planes, and in the design of the
required, but difficult, injection systems. Ring cooling
lattices also have the potential of significantly reduced
cost compared to single-pass cooling systems with
comparable performance. We will present some recent
lattice designs, describing their theory, features, and
performance, including injection and extraction systems.
*Work supported by the Department of Energy, contract
DE--AC02--98CH10886.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1850 - Longitudinal Beam Dynamics in ImperfectlyIoschronous FFAG Accelerators*
J.S. Berg, BNL, Upton, Long Island, New York
Using FFAGs for the arcs of recirculating accelerators has
the potential to achieve significant cost savings over a
multiple-arc design. The problem with such a design is
that no FFAG arc will have the same path length over its
entire energy range. This leads to problems with
synchronizing high-frequency RF with the beam on each
pass. It has been demonstrated [1] that in fact a reference
particle can be accelerated in such a system for an
arbitrary number of turns, although the amount of linac
required for a given energy gain never falls below a
certain nonzero value for a larger number of turns. Here
we examine the longitudinal phase space acceptance of
such a system as a function of the number of turns in the
accelerator.
*Work supported by the Department of Energy, contract
DE--AC02--98CH10886.
[1] J. Scott Berg. Longitudinal Reference Particle Motion
in Nearly Isochronous FFAG Recirculating Accelerators.
To appear in the proceedings of Snowmass 2001, 30 Jun21 Jul 2001, Snowmass Village, CO.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1216 - Extraction by Stripping at JINR
O. Borisov, JINR, Dubna, Moscow Region
1 /52
Numerical simulation results of the heavy ions extraction
by stripping for various magnetic structures, chageexchange ratio and other parameters are considered. The
possibilities and advantage of this extraction method are
discussed. Experimental results for U-400 and U-400M
cyclotrons are present.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
off the second harmonic RF system. During the process,
the peak current is temporarily increased, which makes it
suitable only to improve the situation in a receiving
machine (in our case the PS) after transfer. In practice, the
set-up of this new scheme turned out to be fast and simple
and to yield reliable and reproducible results.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
250 - Field Quality vs Beam Based Corrections in
Large Hadron Colliders
O.S. Bruning, CERN, Geneva
The paper discusses limits for correcting the magnet field
quality via dedicated correction circuits in a collider
storage ring and the possibility of adjusting the powering
of such correction circuits via beam based measurements.
Type of presentation requested : Invited Paper
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1378 - Coupling Correction for the SNS Accumulator
Ring
N. Catalan-Lasheras, CERN, Geneva; C. Gardner, I.
Papaphilippou, G. Parzen, BNL, Upton, Long Island,
New York
In high intensity machines as the SNS accumulator ring,
coupling resonances combined with the space-charge
effect may produce excessive emittance growth leading to
intolerable beam losses. Several correction schemes have
been investigated to achieve local and global decoupling
and the correction of vertical dispersion. A minimal set of
skew quadrupole correctors and their maximum strength
have been defined. The final configuration robustness and
sensitivity for all the potential working points has been
tested and the results are discussed.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1632 - Measurement and Correction of Imperfections
in the SLS Storage Ring
M. Böge, V. Schlott, A. Streun, PSI, Villigen
Based on precise average beta function measurements
with errors of ~1 % for the locations of the 174
quadrupoles an SVD based beta beat correction has been
applied using the individually powered quadrupoles as
correctors. Residual horizontal and vertical beta beats of 4
and 2 % have been measured after correction. Beam based
alignment techniques have been applied to determine
BPM centers with respect to adjacent quadrupoles.
Furthermore the analysis of Corrector/BPM response
matrices within a parameterized model gives a detailed
understanding of the underlying imperfections. The
foreseen SVD based beam based girder alignment adjusts
the 48 magnet girders in order to minimize the closed
orbit distortions. Linear encoders allow to monitor the
movement of BPMs and girders once the imperfections
have been corrected.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
520 - Creation of Hollow Bunches by Redistribution of
Phase Space Surfaces
C. Carli, M. Chanel, CERN, Geneva
The creation of hollow bunches in the longitudinal phase
space, in order to decrease the peak current and in turn the
transverse direct space charge forces, is an old idea. A
new method to create such hollow a distribution at high
energy has been simulated and tested experimentally at
the PS Booster synchrotron. It is based on a redistribution
of surfaces in the longitudinal phase space by using a
double harmonic RF system. During the process, the
beam is transferred from one second harmonic sub-bucket
to the other. Low density phase space surfaces from the
periphery and high density regions from the centre are
exchanged, leading to flat profiles, even after switching
270 - Downstream Beamline for the 2-us, 2-kA and 20MeV DARHT-II*
Y.-J. Chen, L. Bertolini, G.J. Caporaso, A. Paul, B. Poole,
L.-F. Wang, G.A. Westenskow, LLNL, Livermore
The second-axis of the Dual-Axis Radiographic
Hydrodynamic Test facility (DARHT-II) is to perform
multiple-pulses x-ray flash radiography. The DARHT-II
accelerator will provide a 2-kA, 20-MeV and 2microsecond electron beam with a ± 0.5% energy
variation. We have designed a beamline to select several
short current pulses from the 2-microsecond beam and to
deliver those pulses to a x-ray converter target. The
remained beam will be delivered to a beam dump. With
the diagnostic beam stop inline, the transport system
provides emittance diagnose capability for the beam
exiting the accelerator. The beamline consists of several
long drift sections. The transverse resistive wall instability
and the background gas focusing effects in the long drift
sections could be potential problems for maintaining the
quality of the long pulse, high current beam. The beam
exiting the accelerator has a rise time of 50 - 150 ns with
the beam head energy varying from 16 - 20 MeV. Gas
desorption caused by beam spill of the long off-energy
beam head is also a concern. We will present the
beamline configuration and its beam parameter
acceptance, the transverse resistive wall instability
modeling, the final spot size variation caused by the
background vacuum, and the simulations of beam spill.
The beam spot size on the target will be discussed.
2 /52
*This work was performed under the auspices of the U.S.
Department of Energy by University of California
Lawrence Livermore National Laboratory under contract
No. W-7405-Eng-48.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1231 - Measurement of Optical Functions in HERA
W. Decking, B. Holzer, J. Keil, T. Limberg, DESY,
Hamburg
The linear optics of both HERA electron and proton ring
have been measured with several methods, including
gradient changes in individual powered quadrupoles, local
orbit changes in the arc sextupoles and response matrix
fitting. Only a combination of all methods allows a
complete understanding of the linear optics. Automated
data taking and analysis has proven to be an important
tool in the re-commissioning of HERA and revealed
several optics errors. A review of the methods and results
of the measurements will be presented.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1227 - Studies for Beam Lifetime Optimization in
DAFNE
S. Guiducci, INFN-LNF, Frascati (Roma)
Since the DAFNE beam lifetime is strongly dominated by
the Touschek effect, an analysis of its dependence on the
ring dynamic aperture and on machine parameters has
been done in order to improve the machine performances.
Measurements taken in different conditions are here
presented and compared with simulations. The agreement
is quite satisfactory when taking into account the
measured bunch length and machine coupling, and the
actual dynamic aperture.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
311 - The Influence of Time-Dependent Magnetic
Field Errors on the Specifications of Feedback and
Collimation Systems
M. Hayes, R.W. Assmann, J. Wenninger, CERN, Geneva
The LHC requires an excellent beam stability during all
phases of the LHC cycle. This stability must be ensured
inspite of the time-dependent field errors in the
superconducting main dipoles. The field errors will
change significantly during injection and ramp, inducing
perturbations of the circulating beam. The known timedependent field errors of the LHC magnets and their
effects on the LHC beam were simulated using latest
tracking codes, allowing the prediction of the beam
stability during injection and ramp. Using these results the
constraints and specifications for beam collimation and
the LHC orbit feedback are studied.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1148 - A Generalized Orbit Correction Scheme
E. Karantzoulis, F. Iazzourene, L. Tosi, ELETTRA,
Trieste
The special operating conditions of ELETTRA have
strongly influenced the orbit correction philosophy. A
hybrid orbit correction scheme is presented whereby local
orbit corrections at arbitrary positions and angles at three
light source points of each of the eleven user dedicated
sections are performed that also maintain the global orbit
stable. The method, the stability and the implications are
presented and discussed.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1035 - Ionization Cooling of Muon Beams
E.-S. Kim, PAL, Pohang
We present an ionization cooling lattice design which use
solenoidal focusing channels and liquid hydrogen
absorber wedge for the transverse and longitudinal
cooling of muon beams. The cooling performances in the
cooling system are investigated.
Type of presentation requested : Poster
Speaker :
Eun-San Kim
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
420 - Vertical Beam Size Control at SRRC
C.-C. Kuo, H.P. Chang, H.J. Tsai, SRRC, Hsinchu
Vertical beam size control in the 1.5 GeV synchrotron
radiation storage ring at SRRC was investigated. Linear
coupling model with measured orbit response was
attempted. Manipulation of transverse beam betatron
coupling as well as the vertical dispersion correction
using a set of skew quadrupoles around the ring has been
conducted. The correlation of the coupling strength,
vertical beam size, beam brightness, as well as beam
lifetime was measured and optimal operation conditions
have been searched for the routine users operations.
Type of presentation requested : Poster
Speaker :
C. C. Kuo
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1321 - Vertical Emittance Control at BESSY
P. Kuske, BESSY, Berlin
In synchrotron radiation light sources like BESSY II the
reduction of the vertical emittance can increase the
brilliance of the photon beam, can improve the resolution
of certain monochromators, and is required for the
planned production of femto second light pulses based on
bunch slicing [1]. On the other hand running the storage
ring with only a few bunches favors a larger vertical
emittance in order to reduce the particle density and
3 /52
Touschek losses. Thus flexible control of the vertical
emittance is highly desirable. The paper describes the
steps taken to accomplish this goal. The small vertical
emittance is achieved by beam based alignment, analysis
of the orbit response matrix in order to find suitable
locations for skew quadrupole magnets, the minimization
of the vertical dispersion, and the decoupling of the
transverse planes by observing and correcting the local
normal modes at 63 beam position monitors. In the single
bunch mode the vertical emittance is increased by
exciting an artificial difference coupling resonance with a
time varying skew gradient field produced by strip lines.
This approach has certain advantages over other
techniques used for blowing up the beam.
[1] S. Khan, private communication
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
27 - Beam Matching Section for the Superconducting
COSY Injector LINAC
A. Lehrach, H. Jungwirth, R. Maier, S. Martin, R. Tölle,
FZJ, Jülich
As a new injector for the Cooler Synchrotron COSY in
Jülich a superconducting LINAC is being designed and
constructed to provide intense beams of polarized protons
and deuterons [1]. Beam dynamics calculation have been
carried out to find an optimized configuration for beam
matching between RFQ and LINAC. Therefore several
different field arrangements have been discussed. In this
paper the results of the beam dynamics calculations are
presented and the capability of the matching section is
discussed.
[1] Conceptual design report 'Superconducting Injector
LINAC for the Cooler Synchrotron COSY',
Forschungszentrum Juelich, Internal report (2001).
Type of presentation requested : Poster
Speaker :
A. Lehrach
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1468 - Measurement of the LNLS Electron Storage
Ring Beam Acceptance
L. Liu, T. Costa, LNLS, Campinas
We describe a method to determine the parameters of the
beam acceptance in phase space in a storage ring using
basically a kicker and current measurement. We present
and discuss the results of the measurements performed on
the LNLS UVX electron storage ring.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
64 - Emittance Exchange by Crossing a Coupling
Resonance
E. Metral, C. Carli, G. Cyvoct, M. Giovannozzi, G.
Metral, R. Steerenberg, CERN, Geneva
When the working point of a synchrotron is shifted across
a second-order difference resonance in the presence of
weak linear coupling, it is possible to exchange the
transverse emittances. This result goes beyond the
classical theory, where only emittance sharing is
predicted. Systematic experimental investigations of the
phenomenon have been performed at the CERN PS
Complex. In the PS-Booster, the measurement of the
horizontal emittance is hampered by the contribution of
the momentum spread to the beam size through
dispersion. Based on the new mechanism, the horizontal
emittance was measured in the vertical plane, where no
dispersion is present, thus improving the overall accuracy.
In the PS, detailed measurements of the emittance
exchange process were performed. In parallel, an
analytical theory was derived. The agreement between
theory and experimental results is remarkable.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1014 - Low Emittance Lattice Upgrades for the Duke
FEL Storage Ring (*)
S. Mikhailov, V. Litvinenko, Y. Wu, DFELL, Durham
In this paper we present two versions of possible upgrade
of the lattice of the 1 GeV Duke FEL Storage Ring
reducing horizontal beam emittance from existing 18
nm*rad to 1.4 nm*rad and 0.9 nm*rad respectively. One
of proposed lattices reuses existing magnetic elements,
another is based on completely new design. The use of
combined function magnets with dipole, quadrupole and
sextupole components allows us to keep the ring compact
and fit it into existing footprint. We present the results of
2D and 3D magnet design and field simulations for such a
magnet. Results for dynamic aperture simulations are also
presented. We also discuss the choice of lattice cell and
tune advances and the concept of local compensation of
nonlinear aberrations.
(*) This work is supported by the Dean of Natural
Sciences (Duke University)
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
738 - Degrees of Freedom Determination in
Accelerator Physics Optimisation Problems Subject to
Global Constraints
A.-S. Mueller, CERN, Geneva
The determination of the number of degrees of freedom of
a system is a common problem in physics. It is
straightforward for the case of unbounded parameters. For
global constraints cutting into the parameter space
however, the determination is difficult. This problem
occurs, for example, in the matching of beam lines where
global constraints like aperture or maximum bend angle
have to be respected. It is also relevant for fits of complex
models to experimental data, where external information
(e.g. positivity, maximum energy loss or measured
momentum spread) is included in the form of constraints.
4 /52
This paper proposes a method to extract the effective
number of degrees of freedom for a given system.
Examples are discussed to illustrate the method.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1475 - Simulation and Correction of the Closed Orbit
Distortion for the New Lattice of SOLEIL*
A. Nadji, SOLEIL, Orsay
The SOLEIL lattice has been modified in order to satisfy
the growing interest in the use of undulators as the
privileged photon sources [1]. The sensitivity of the new
optics to dipolar errors has been studied. The expected
values of horizontal and vertical orbit distortions are
calculated analytically using statistical formulae and
computed with a tracking program (BETA) in order to
take into account the effects of the sextupoles. The
number and the location of beam position monitors and
correctors have been revisited. As for the estimation of
the errors, their correction is also performed both
analytically (which is particularly interesting during the
elaboration of a project) and numerically (which allows to
control the restoring of the dynamic aperture).We report
here the results of the correction, using SVD method,
from a comparative study using a minimum necessary
number of correctors and all the available ones. The
dipolar correctors are coils installed inside sextupoles.
Special attention is paid to the effect on the dynamic
aperture of inevitable extra multipolar components
introduced by these dipolar correctors.
*work supported by Synchrotron SOLEIL
[1] A modified lattice for SOLEIL with a larger number
of straight sections, A. Nadji, P. Brunelle, J. M. Filhol and
M. P. Level
Shanghai Symposium on Intermediate Energy Light
Sources, 23-26 September 2001
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1338 - Analysis and Correction of Optical Asymmetry
at the ESRF
R. Nagaoka, L. Farvacque, ESRF, Grenoble
The correction of optical asymmetry due to quadrupole
errors is of great importance for the required beam quality
at the ESRF. With the conventional orbit response matrix
approach, effective quadrupole errors are extracted.
Following the success of using the skew components
obtained in this way with the off-diagonal matrix to
correct the coupling, an online correction of optical
asymmetry is attempted using a partial response matrix.
Results are compared with the empirical correction of the
nearest half-integer resonances that has conventionally
been performed. Resonance stopbands are computed at
each stage on the basis of the obtained quadruple error
distribution and their utilisation in the minimisation
procedure is considered. A thousand-turn BPM diagnostic
implemented at the ESRF is used to measure
independently the optical asymmetry. Attempts made to
trace the origin of errors are also discussed.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1441 - Electron Bremsstrahlung Characteristics
Calculation Model for a Multi-layer Conversion
Target Placed in a Hyperbolic Magnetic Field
A. Nesterovich, P. Alferov, V. Kudinov, A. Savostyanov,
V. Smirnov, MEPhI, Moscow
The description of an electron bremsstrahlung
characteristics calculation model for a multi-layer
conversion target, placed in a hyperbolic magnetic field is
presented. The bremsstrahlung characteristics at electron
energy up to 300 MeV from 10-layer copper target are
obtained. The thickness of each layer is equal to 0,05
radiation length. Quadrupole magnetic triplets are located
between layers. It is shown, that the bremsstrahlung
source intensity with use of offered magnetic system
grows almost in 1,8 times for registration angle equal
to1O. For the numerical decision of equation of the
charged particles movement in the magnetic field, given
by a magnet, the linear difference method for a Koshi task
approximation
for first order ordinary differential
equations system the was used.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1452 - Possibility of an Electron Bremsstrahlung
Output Increase by Use of a Conversion Target placed
in a Focusing Magnetic Field
A. Nesterovich, P. Alferov, V. Kudinov, Y. Pomazan, V.
Smirnov, MEPhI, Moscow
The dependences of bremsstrahlung output at electron
energy about 100-300 MeV upon multi-layer target,
placed in a focusing magnetic field, thickness are
presented. The system suggested is intended for an
intensive bremsstrahlung flow formation on objects,
which are removed from radiator on significant distance.
Such radiator, in particular, can be used at monitoring the
Earth atmosphere from space and at sounding planets with
the help of space vehicles. It is shown, that the
bremsstrahlung output from 10-layer copper target, placed
in a focusing magnetic field, exceeds in 3 times the one
from an optimum target for a registration angle of 10. The
magnetic field influence on bremsstrahlung angular
distribution width is investigated.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1053 - Measurement of XY Coupling at I.P using
Turn-by-turn BPM
Y. Ohnishi, Y. Funakoshi, M. Tejima, M. Tobiyama, KEK,
Ibaraki-ken
5 /52
We have measured the xy coupling of the interaction
point (I.P) at KEKB. The horizontal or vertical betatron
oscillations can be measured by a turn-by-turn BPM in
the laboratory coordinate system when a normal mode is
excited by a shaker with tune frequency. A harmonic
analysis has been performed to measure the xy coupling
parameters and compared with a measurement from
single kick orbit.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
order. In the case of very low beam intensities such as for
radioactive beams in which small losses are still
acceptable, it is convenient to consider systems with only
two cells, which don't give the exact solution, but still
maintain a reasonable beam quality. We present here a
comparison between the four and two cell systems applied
to the ISAC-II case in which the range of charges
transported is ±5% from the reference one.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1478 - New Stability Regions for Periodically Focused
Particle Beams*
R. Pakter, ULBRA, Canoas; F. Rizzato, UFRGS, Porto
Alegre
A key aspect of periodically focused beams is their
stability properties. Previous studies revealed that above a
certain threshold of the focusing field strength the
matched (equilibrium) solution looses stability, imposing
severe limitations to the practical use of periodical
focusing. In this paper, we perform a detailed stability
analysis of periodically focused intense particle beams
based on the beam envelope equation. It is shown that
although the original matched solution analyzed in
previous works becomes unstable and eventually vanishes
as the focusing field strength increases, stability is
recovered for yet larger fields because new matched
solutions emerge. The scenario as one increases the
focusing field is thus not the existence of a single
threshold above which confinement is impossible, as
believed so far, but the existence of regions of stability
interrupted by gaps where the matched solution either
becomes unstable or completely absent [1]. We also show
that one can effectively focus beams to tighter radii using
the new stable matched solutions. Results are validated
with self-consistent simulations.
* Work supported by CNPq, Brazil.
[1] R. Pakter and F. B. Rizzato, Phys. Rev. Lett., 87,
044801 (2001).
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
957 - Coupling Analysis and Correction at RHIC
F. Pilat, J. Beebe-Wang, W. Fischer, V. Ptitsyn, T.
Satogata, BNL, Upton, Long Island, New York
Coupling correction at RHIC has been operationally
achieved through a two-step process: using local triplet
skew quadrupoles to compensate coupling from rolled
low-beta triplet quadrupoles, and minimizing the tune
separation and residual coupling with orthogonal global
skew quadrupole families. An application has been
developed for global correction that allows skew
quadrupole tuning and tune display with a choice of
different tune measuring techniques, including tunemeter,
Schottky and PLL. Coupling effects have been analysed
by using 1024-turn turn-by-turn (TBT) information from
the beam position monitor (BPM) system. Injection
decoherence data allow the reconstruction of the offdiagonal terms of the transfer matrix, a measure of global
coupling at injection. At both injection and storage
energies, coordination of tunemeter kicks with TBT
acquisition at 322 BPMs in each ring allows the
measurement of local coupling at all BPM locations.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1720 - An Isopath Achromatic Bending Section for
Multi-charge Ion Beam Transport at ISAC-II
M. Pasini, R. Laxdal, TRIUMF, Vancouver
The ISAC-II post accelerator at TRIUMF has been
optimized to allow the simultaneous acceleration of ions
with multiple charge states after stripping to preserve
beam intensity of the exotic species. Bending sections,
required to provide charge selection, fit building layouts
or to transport beam to the experimental station, are
constrained to have equal path length (isopath condition)
for all charge states to maintain bunch structure. In
addition they have to maintain a high order of
achromaticity to prevent transverse emittance growth. An
isopath system of four optics cells with proper symmetry
conditions will fulfill the achromatic condition to high
878 - Recent Development and Progress in the
UNILAC High Intensity Upgrade Program
S. Richter, W. Barth, L. Dahl, J. Glatz, L. Groening, GSI,
Darmstadt
In the framework of the beam intensity upgrade program
of GSI the UNILAC was modified to accelerate intense
heavy ion beams under space charge conditions. This
paper gives an overview on the highest ion intensities
achieved and on recent beam line improvements. During
2001 beam intensities of up to 15 emA Ar10+ were
achieved demonstrating that the design intensities were
met for ions of intermediate mass numbers. For the
heaviest ions like U73+ intensities of 0.5 emA were
obtained so far and a further increase to the design
intensity of 4.6 emA is envisaged for the future.
In the beginning of 2002 the focussing strength during
beam acceleration in the Alvarez section was optimized in
order to reduce the space charge induced growth of
transverse beam emittances. The reduction from 15 to 10
Single-Gap-Resonators allowed the introduction of
alternating phase focusing and the elimination of the
strong magnetic focusing by dc quadrupoles in the
6 /52
resonators. Beam dynamics behavior now resembles that
of a drift space. Despite of the reduction any desired
energy in the range of 3.6 to 13 MeV/u (uranium) can still
be obtained from seven discrete Alvarez tank output
energies. Two recently installed octupole magnets in the
beam line for the super heavy element production setup
(SHIP) allow the flattening of an initial Gaussian beam
shape to a nearly rectangular transverse density
distribution. This permits to increase an integrated ontarget-intensity by a factor of three.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1744 - MATLAB-based LOCO
J. Safranek, G. Portmann, A. Terebilo, SLAC SSRL,
Stanford
The storage ring linear optics debugging code LOCO [1]
has been rewritten in MATLAB and linked to the
accelerator modeling code AT [2]. LOCO uses the
measured orbit response matrix to determine quadrupole
gradients. A MATLAB GUI provides a greatly improved
user interface with graphical display of the fitting results.
The option of including the shift in orbit with rf frequency
in the orbit response matrix has been added, so that the
dispersion is included in the fit. This facilitates control of
the horizontal dispersion, which is important for
achieving small horizontal emittance. Also included are
error bar calculation, outlier data rejection, accomodation
of single-view BPMs, and the option of including
coupling in the fit. The code was written to allow linking
to other accelerator modeling codes.
[1] J. Safranek, Nucl. Inst. and Meth. A388, 27 (1997).
[2] http://www-ssrl.slac.stanford.edu/at/
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1023 - Linear Optics during the RHIC 2001-2 Run*
T. Satogata, J. Cardona, V. Ptitsyn, S. Tepikian, J. van
Zeijts, BNL, Upton, Long Island, New York
The RHIC 2001-2 Au and polarized proton runs used
several different low-beta optics configurations. Low-beta
squeezes were routinely performed through the Au
acceleration ramp to optimize injection and transition
optics; the polarized proton run injected and accelerated
with constant low-beta optics to optimize polarization
efficiency. Dispersion analysis were successfully used to
diagnose power supply miswirings early in the Au run.
This paper summarizes tools, methods and results for
linear optics measurement and correction during these
runs.
Work performed under the auspices of the US Department
of Energy
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1025 - Model-Independent Analysis Methods Applied
to RHIC Injection*
T. Satogata, W. Fischer, J. van Zeijts, BNL, Upton, Long
Island, New York
During the RHIC 2001-2 Au and polarized proton runs,
orbit data were routinely acquired for injected tuning
bunches in the AGS to RHIC transfer line (ATR) and at
all beam position monitors (BPMs) in each RHIC ring.
Few parameters were changed, usually limited to injection
dipole steering magnets during a typical tuneup of 10-20
pilot bunches. Though these statistics are low, the 1000+
turns of orbit data acquired at all RHIC BPMs for each
injection are analyzed using singular value decomposition
and model-independent analysis techniques to give
information about RHIC BPM performance, injection
pulsed-element and ATR performance, and RHIC
injection optics.
* Work performed under the auspices of the US
Department of Energy
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1554 - Simulation of Dark Current Transport through
the TESLA Test Facility Linac
H. Schlarb, DESY, Hamburg
The transported dark current in a high-duty cycle
accelerator as the TESLA Test Facility linac (TTF) could
significately condtribute to radiation damages of
components along the beamline. In the past high dark
currents emitted from the laser driven RF-gun have been
observed during substantial time of linac operation. For a
better understanding of the dark current transported
through and lost in the entire linac numerical simulations
are compared with experimental data. To identify possible
locations for collimators to remove the dark current from
the beamline the beam and its halo have been investigated
in details. The operation of an absorber recently installed
in the dispersive section of TTF magnetic bunch
compressor and its impact on the downstream collimator
section is discussed.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1621 - Modelling the Magnet Lattice of the Dortmund
Electron Accelerator
G. Schmidt, U. Berges, J. Friedl, M. Grewe, D. Schirmer,
T. Weis, K. Wille, D. Zimoch, DELTA, Dortmund
The Dortmund Electron Accelerator (DELTA) is a 1.5
GeV synchrotron light source. DELTA uses a strong
focusing magnet structure. The distance of magnets is
small and quadrupoles, steerers and sextupoles use the
same magnet yoke. Magnet fields were measured taking
into account the interference of the different type of
fields. The modelling finally uses beam based methods to
measure beta-functions and to adapt the lattice model.
The methods and results will be presented.
Type of presentation requested : Poster
7 /52
Speaker :
Mr. Marc Grewe
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
690 - Design of the Conventional Magnets for BEPC-II
C. Shi, Z. Cao, G.L. Ni, Y. Sun, Z. Yin, IHEP, Beijing
Beijing Electron Positron Collider (BEPC) is now
undergoing an upgrade program, BEPC-II project. Which
will be upgraded to a double ring machine in the near
future. The paper brief introduces conceptual design of
several kind conventional magnets for BEPC-II. The
magnetic field calculation and structure design of are
describled in this paper. Also given is the basic
parameters of the magnets.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
666 - Improvement of Beam Stability of SPring-8
Storage Ring by Symmetry Restoration
Hitoshi Tanaka, N. Kumagai, S. Matsui, J. Schimizu, K.
Soutome, M. Takao, H. Takebe, K. Tsumaki,
JASRI/SPring-8, Hyogo; K. Kumagai, RIKEN, Saitama
In general, it is known that the distortion of beam optics
excites accidental resonance lines near an operation point
and hence it limits the stability of circulating beams.
Through 4 by 4 beam response analysis we have recently
seen that the optics distortion in the SPring-8 storage ring
is increased after the modification to install four magnetfree long straight sections of 27m [1] and the r.m.s.
distortion reaches to 7~8 % of a design value. Particle
tracking also showed that this distortion limits the beam
stability especially at the large amplitude of a betatron
oscillation. To improve the beam stability, we have
investigated the correction scheme based on the beam
response analysis. And then, we have found that the small
adjustment on strength of the twelve quadrupoles
suppresses the distortion down to ~1% and recovers the
beam stability sufficiently. In this paper, we will present
our correction scheme and discuss the obtained results
compared with the simulation ones.
[1] H. Tanaka et. al., to be published in N.I.M.
Type of presentation requested : Poster
Speaker :
Dr. Hitoshi Tanaka
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1289 - Lifetime Measurements at MAX II
E. Wallén, Å. Andersson, G. LeBlanc, University of Lund,
Lund
A set of measurements with moveable aperture
restrictions combined with varying the bunch size in the
1.5 GeV electron storage ring MAX II has been carried
out. The measurements make it possible to make a
distinction between the Touschek lifetime and the vacuum
lifetime limitations. The work has been carried out in
order to find out what minimum gap that can be tolerated
for new insertion devices in MAX II and similar storage
rings.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
378 - Optics Measurements at the SPS Using Closed
Orbit Response
J. Wenninger, CERN, Geneva
As an injector for the LHC collider, the SPS must
accelerate and extract very intense and bright beams. First
optics measurements have been performed using the orbit
response to steering magnet kicks. The data was analysed
with the LOCO program in order to refine the machine
optics model. First tests of this procedure for the very
long transfer lines between the SPS and the LHC will
also be presented.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
268 - Design of the DARHT-II Downstream Beamline*
G.A. Westenskow, L. Bertolini, Y.-J. Chen, A. Paul, LLNL,
Livermore
This paper describes the mechanical design of the
downstream beam transport line for the second axis of the
Dual Axis Radiographic Hydrodynamic Test (DARHT-II)
Facility. The DARHT-II project is a collaboration
between LANL, LBNL and LLNL. DARHT II is a 18.4MeV, 2000-Amperes, 2-microsecond linear induction
accelerator designed to generate short bursts of x-rays for
the purpose of radiographing dense objects. The downstream beam transport line is approximately 22-meter
long region extending from the end of the accelerator to
the bremsstrahlung target. Within this proposed transport
line there are 12 conventional solenoid, quadrupole and
dipole magnets; as well as several speciality magnets,
which transport and focus the beam to the target and to
the beam dumps. There are two high power beam dumps,
which are designed to absorb 80-kJ per pulse during
accelerator start-up and operation. Aspects of the
mechanical design of these elements are presented.
* This work was performed under the auspices of the U.S.
Department of Energy by the University of California,
Lawrence Livermore National Laboratory under Contract
No. W-7405-Eng-48.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
269 - Performance of the FXR Accelerator*
G.A. Westenskow, Y.-J. Chen, G. LeSage, M. Ong, J.M.
Zentler, LLNL, Livermore
The FXR induction accelerator is used as a radiographic
tool at LLNL to produce short intense x-ray pulses.
During the past year we have studied the performance of
the accelerator in an attempt to reduce the final beam spot
size. We will report on various measurements of the
beam's emittance and energy spread. We have made time
8 /52
resolved measurements near the injector and at the end of
the accelerator. To produce smaller spots at the x-ray
converter target we will need to modify the pulse power
drive system to reduce the voltage variations on the
induction cells during the pulse. We are also performing
simulations of the injector to understand the large
emittance that was measured.
*This work was performed under the auspices of the U.S.
Department of Energy by the University of California,
Lawrence Livermore National Laboratory under Contract
No. W-7405-Eng-48.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1651 - Beta Function Measurements in the PEP-II
Low Energy Ring
U. Wienands, SLAC, Stanford; M.E. Biagini, INFN-LNF,
Frascati (Roma)
The Low Energy Ring of PEP-II has 90-degree cells in
the arc sections which prevent the measurement of the
beta functions using the local method as implemented e.g.
at LEP by P. Castro et al. We present a modified
algorithm that is able to circumvent this restriction and
has proven to give reliable results. The improved
algorithm has been used to diagnose changes in the beta
functions especially in response to different setups of the
machine. In particular, a significant beta beat developed
when changing the horizontal working point towards 0.5,
the origin of which is presently under study.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
856 - Initial Results from Model Independent Analysis
of the ATF*
A. Wolski, A. Jackson, LBNL, Berkeley
Model Independent Analysis (MIA) has shown the
potential to be a useful tool for diagnostics and optics
verification.
The Accelerator Test Facility (ATF)
prototype damping ring at KEK has a diagnostic system
with the ability to collect data allowing the application of
MIA for analysis of the optics and beam properties,
including stability of the injection energy and transverse
action. Understanding of the optics (particularly the
coupling), and of the injection stability, is important for
improving the operational performance of a damping ring,
in terms of the emittance and injection efficiency. MIA
affords the opportunity for study of these features, which
may be difficult to assess by other means. We report here
the results of an initial attempt to apply MIA to the ATF.
*Work supported by the US DOE under contract DEAC03-76SF00098
DISCLAIMER
This document was prepared as an account of work
sponsored by the United States Government. While this
document is believed to contain correct information,
neither the United States Government nor any agency
thereof, nor The Regents of the University of California,
nor any of their employees, makes any warranty, express
or implied, or assumes any legal responsibility for the
accuracy, completeness, or usefulness of any information,
apparatus, product, or process disclosed, or represents that
its use would not infringe privately owned rights.
Reference herein to any specific commercial product,
process, or service by its trade name, trademark,
manufacturer, or otherwise, does not necessarily
constitute or imply its endorsement, recommendation, or
favoring by the United States Government or any agency
thereof, or The Regents of the University of California.
The views and opinions of authors expressed herein do
not necessarily state or reflect those of the United States
Government or any agency thereof, or The Regents of the
University of California.
Ernest Orlando Lawrence Berkeley National Laboratory
is an equal opportunity employer.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1700 - Beam Stabilization in the SLAC A-line Using a
Skew Quadrupole*
M. Woodley, P. Bosted, F.-J. Decker, R. Erickson, M.
Libby, M.B. Woods, SLAC, Stanford
The E158 experiment at SLAC is a precision
measurement of the left-right asymmetry in Moller
scattering at low Q**2 utilizing a high-current long-pulse
polarized electron beam scattering off unpolarized
electrons in a liquid hydrogen target. Tolerances on beam
size and position/angle stability for E158 are extremely
tight, but the electron beam is subject to intensity jitter,
dispersion, and wakefield effects in the linac which tend
to make it unstable. Horizontal emittance growth due to
synchrotron radiation in the transport line from the linac
to the target ("A-line") reduces the sensitivity of the
horizontal beam parameters at the target to incoming
changes, but instability in the vertical plane was observed
during the E158 pilot run. A skew quadrupole recently
installed in the A-line just upstream of the target will be
used to couple the projected transverse emittances,
increasing the vertical emittance of the beam and thereby
reducing its sensitivity to incoming changes. Simulations
of the use and effects of this skew quadrupole, along with
measured beam performance data with and without the
skew quadrupole, will be presented.
*Work supported by the U.S. Department of Energy
under contract DE-AC03-76SF00515.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1328 - The Design of the Isochronous and Achromatic
Charge-Stripping Sections for RIA"*"
X. Wu, D. Gorelov, T.L. Grimm, W. Hartung, F. Marti, H.
Podlech, R.C. York, NSCL, East Lansing
9 /52
The proposed Rare Isotope Accelerator (RIA) uses a
superconducting, cw linac to accelerate light and heavy
ions to final energies of 400 MeV/u or more with a beam
power of 100 to 400 kW. To meet the beam power
requirements, simultaneous acceleration of several charge
states is proposed for the heavier ions. For example, for
U238, two charge states of 28+ and 29+ would be
accelerated to an energy of about 13 MeV/u where the
beam would be stripped and collimated to retain five
charge states (73+ to 77+). These five charge states
would then be accelerated to an energy of approximately
83 MeV/u where the beam would again be stripped and
collimated to retain three charge states (87+ to 89+) that
would be accelerated to the final energy of 400MeV/u.
The optics design and simulation results for the two
isochronous and achromatic charge-stripping sections are
presented.
"*" Work supported by Michigan State University and
NSF PHY 0110253.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1711 - An SVD Enhanced Fitting for e+/e- Storage
Ring Linear Optics Verification and Correction
Y. Yan, Y. Cai, J. Irwin, M. Sullivan, SLAC, Stanford
We use an SVD-enhanced least square fitting method to
fit the phase advances and the Green's functions
(specified by the local transfer matrix components R12,
R34, R32, and R14) calculated from the lattice model to
the corresponding measurements from turn-by-turn Beam
Position Monitor (BPM) buffered data of a storage ring
using a model-independent analysis (MIA) technique. The
fitting variables are: all of the storage-ring quadrupole
strengths (both normal and skew) and sextupole feeddowns and all of the BPM gains and BPM cross-plane
couplings. Once fitted, the storage ring linear optics is
verified and the magnet strength corrections are obtained,
which would potentially correct the real machine linear
optics to be the same as that of the lattice model.
Furthermore a magnet correction priority sequence in
terms of effectiveness in correcting the real machine
linear optics can be exercised in the computer before
correcting the real accelerator. Results from PEP-II
measurement will be presented.
Work supported by US DOE contract DE-AC0376SF00515.
Type of presentation requested : Poster
Speaker :
Yiton Yan
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
216 - Scaling Relations for the Determination of Beam
Optics Errors using Response Matrix Analysis
V. Ziemann, TSL, Uppsala
Quadrupole gradient errors can be very accurately
determined by carefully analysing difference orbits and
their deviations from computer-model predictions. This
method was successfully applied in synchrotron radiation
sources. In order to allow easy before-hand estimates for
the application to other accelerators we determine scaling
relations for achievable accuracies as a function of BPM
resolution and used number of BPM and dipole
correctors.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
217 - A Proposal to Measure the Duodecapole
Component of the LHC Triplet Magnets using a
Wobbling Method
V. Ziemann, TSL, Uppsala
Due to finite manufacturing tolerances the triplet
quadrupoles used in the interaction regions of LHC will
have non-vanishing multipole errors which need to be
measured and corrected in order to guarantee sufficient
dynamic aperture at collision energy. Here we discuss a
method to measure the unwanted multipole components
by oscillating a closed orbit bump in the interaction
region and observing the orbit at pickups outside the
bump. The beam's response will contain very weak
signals at harmonic frequencies of the sinusoidal
excitation. Even though the amplitude of the harmonic
signal will be below the resolution of the position monitor
system, it can be made visible by adding noise to the
original pickup data and subsequent careful filtering and
averaging. We use a simple computer model to simulate
the oscillating bump that generates pickup signals and
then analyze those in a sophisticated signal processing
chain in order to retreive the magnitude of the unwanted
multipole components.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
703 - Modelling Nonlinear Optics in the CERN SPS
F. Zimmermann, G. Arduini, P. Collier, CERN, Geneva;
A. Faus-Golfe, IFIC, Valencia
Nonlinear fields arising from eddy currents in the vacuum
chamber and remanent fields in the magnets of the CERN
SPS vary with time and with the acceleration cycle. We
describe a procedure of constructing a nonlinear optics
model for the SPS, by considering sextupolar, octupolar,
and decapolar field errors in the dipole and quadrupole
magnets, respectively, whose strengths are adjusted so as
to best reproduce the measured nonlinear chromaticities
up to third order in the
momentum deviation. Applying this procedure to SPS
chromaticity measurements taken at 26 GeV/c, we have
obtained a refined optics model. The tune shifts with the
transverse amplitude predicted by this model are
consistent with a direct measurement.
Type of presentation requested : Poster
Speaker :
Dr. Angeles Faus-Golfe
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
10 /52
1418 - Beam Based Machine Modelling for Orbit
Control and Feedback
D. Zimoch, M. Grewe, G. Schmidt, T. Weis, K. Wille,
DELTA, Dortmund
The 1.5 GeV electron storage ring Delta uses quadrupole
magnets with integrated sextupoles and steerers to obtain
a compact lattice. However, saturation and hysteresis
effects result in nonlinear interactions between the magnet
components. Therefore, optic models have so far failed to
reproduce the observed optics with the required precision.
We thus used beam based methods to obtain a heuristic
machine model. Beam based calibration has been used to
measure offsets between the signal centers of the beam
position monitors and the magnetic centers of their closeby quadrupoles. Measured response matrices are used as
basis for orbit feedback and local orbit bumps. These
steps have significantly improved machine stability and
reliability.
Type of presentation requested : Poster
Classification : [D01] Beam Optics - Lattices, Correction
Schemes, Transport
1052 - Study of Acceptance of FFAG Accelerator
M. Aiba, T. Adachi, S. Machida, Y. Mori, A. Mutoh, J.
Nakano, C. Ohmori, I. Sakai, Y. Sato, M. Sugaya, A.
Takagi, R. Ueno, T. Uesugi, T. Yokoi, Y. Yonemura, M.
Yoshii, M. Yoshimoto, Y. Yuasa, KEK, Ibaraki-ken; K.
Koba, FNAL, Batavia
The horizontal acceptance of radial sector Fixed Field
Alternating Gradient (FFAG) accelerator is evaluated
analytically and with particle tracking with its
applications to phase rotation and acceleration of
secondary particles in mind. In those machines, it is
essential to accommodate beams with huge momentum as
well as large transverse emittance although the number of
revolution are limited, typically 10 turns or so. FFAG
focusing structure has zero chromaticity, in other words,
betatron tunes are independent of momentum in all
momentum range. On the other hand, it introduces strong
nonlinearity, therefore betatoron tunes have the amplitude
dependence and linearized model easily fails. We first
perform particle tracking and obtain the horizontal
acceptance of the order of 10E4 pi mm-mrad when the
machine parameters are optimized. Then the effects of
isolated resonance and its amplitude dependent tune shift
are analyzed taking phase per cell as a parameter. We will
show systematic results in machine parameter space and
give generalized design priciple.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1537 - Application of the Frequency Map Aanalysis to
the New Lattice of SOLEIL Project*.
M. Belgroune, P. Brunelle, A. Nadji, SOLEIL, Orsay; J.
Laskar, IMCCE, Paris
The SOLEIL lattice has been modified in order to
increase the number of straight sections for Insertion
Devices. The linear and non-linear optics have been
optimised and satisfy as good results as in the APD study.
A deep investigation of the dynamics was performed for
several working points using the frequency map analysis.
This technique enables a better understanding of the nonlinear beam dynamics and the inner complexe structure of
the dynamic aperture which is essential to choose the best
working point.
* Work supported by Synchrotron SOLEIL
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1546 - Non-linear Transverse Beam Dynamics Studies
in the Super-ACO Storage Ring*
M. Belgroune, P. Brunelle, A. Nadji, SOLEIL, Orsay; L.
Nadolski, ALS, Berkeley
Experimental turn by turn beam position measurements
were performed in order to investigate the non-linear
transverse beam dynamics in the Super-ACO storage ring.
The aim of these experiments is to understand the
aperture limiting effects of non-linearities and to complete
the model used in tracking studies. The two aspects of
non-linear beam behavior described here are the
amplitude-dependent tune shift and the phase space
trajectories near and far from resonances. This work was
carried out with open and closed undulators for on and
off-momentum particles. The effects of a strong
octupolar-like component due to quadrupoles fringe field
missing in the model will be highlighted. We will also
show an analysis which enables to make the distinction
between a physical and a dynamic aperture limitation.
* Work supported by Synchrotron SOLEIL
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
372 - Separatrix Formalizm in Super-conducting
Linac Design
A. Bogdanov, R. Maier, Y. Senichev, FZJ, Jülich
Under design of the linear accelerator we use the
accelerating systems with external synchronizing of the
different groups of structures with few number of similar
gaps. The equivalent phase velocity is constant along each
structure and it is changed by step from cavity to cavity.
The particles are sliding down or up relatively of RF wave
in dependence on the ratio between the particles and the
wave velocities. Thus, the particles are never in
synchronism with the equivalent traveling wave, and even
some time they have not instantaneous longitudinal
stability. But due to a proper choice of the RF phase shift
DjRF between the cavities we can create a quasisynchronous motion, and in total we have a stable motion
in the whole accelerator. Such structures are used for the
acceleration of particles with different masses from the
low energy and in the high-energy proton linear
accelerators. These structures are cheaper, since they have
the simpler cavity geometry. However, due to the bigger
phase oscillation the particles are appeared in the
11 /52
nonlinear part of the separatrix, which one causes the
growth of the longitudinal emittance. We developed the
separatrix formalism for the optimized design of such
linear accelerators.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1337 - Simulations and Measurements of Machine
Background at DAFNE
M. Boscolo, S. Guiducci, INFN-LNF, Frascati (Roma)
DAFNE background is dominated by Touschek
scattering. Studies have been carried out to provide a code
reproducing the machine induced background. A
comparison between the background simulation
predictions in the KLOE interaction region and the
corresponding KLOE data has been performed. These
studies show a qualitative agreement between the
expected and measured background rates. Simulations of
new scrapers to be installed in the two rings are presented.
Expected efficiencies on background reduction in the IRs
are also presented. The comparison between the expected
and measured efficiencies of the scrapers is discussed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1392 - Computation of Insertion Device Fields and
Simulation of their Effects on the SOLEIL Storage
Ring*
P. Brunelle, O. Marcouille, A. Nadji, SOLEIL, Orsay
The lattice of the SOLEIL storage ring has been modified
in order to increase the number of straight sections
dedicated for insertion devices up to 21 [1]. Insertions
with different characteristics have been chosen in order to
produce photons in the large energy range from 5 eV to
50 keV at 2.75 GeV. Insertion devices such as high field
wigglers, very long undulators, very small period minigap
undulators and APPLE II type can affect the small
emittance of the beam and the good beamlifetime. In
order to validate the performances of the ring, their effects
on emittance, energy spread, focusing and dynamic
aperture have been studied. The complexity of the
insertion magnetic structure leads to use a calculated field
map generated by RadiaToTrack [2]and introduced in the
ESRF BETA code version, especially to simulate the non
linear effects for on and off-momentum particles.
* Work supported by SYNCHROTRON SOLEIL
[1] A. Nadji, P. Brunelle, J.-M. Filhol and M.-P. Level,
"A modified lattice for SOLEIL with a large number of
straight sections", Shanghai Symposium on Intermediate
Energy Light Source, 23-26 september 2001.
[2] P. Elleaume, RadiaToTrack version 1.6.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
449 - Fundamental Aspects of the Moment Problem
for a Particle Density evolving under Non-linear
Forces
J.-M. De Conto, C. Peaucelle, ISN, Grenoble
A statistical description (moments) of a beam can be
foreseen to study its evolution when the force is not
linear. In this case, higher order moments must be
estimated from the known moments. We present the
fundamental aspects of this problem, showing how high
order moments can be extrapolated by using orthogonal
polynomials associated to the beam density, in a twodimension phase space, and showing what kind of
maximum information can be obtained from a finite
number of moments. In particular, this gives a good
estimate of the particle localisation and density. Its shows
also the limits of such methods.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
600 - Analytical Formalism for the Longitudinal
Acceleration including Particle Velocity Changing
Effect*
M. Doleans, S.-H. Kim, E. Tanke, ORNL, Oak Ridge
To calculate the energy gain of a particle passing through
an accelerating element, the Panofsky equation which
introduces the concept of transit time factor and average
phase is widely used. For the transit time factor the
assumption of a constant beta through the element is
usually made. In the case of large acceleration or long and
complex accelerating element this approach can lead to
some inaccuracies. To address this problem a method
taking into account the variation of the beta within the
accelerating element has been developed. This method is
applicable to any element by using decomposition of the
electrical field into fourier components. The average
phase concept is adapted to the new formulation and the
passage from the physical entrance phase to the average
phase is clearly stated. The energy gain and time of flight
functions are analytical and allow the treatment of a
bunch of particles by expansion around a reference
particle. The accuracy of the method is presented by
comparison with a slow and precise numerical approach.
*SNS is managed by UT-Battelle, LLC, under contract
DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1598 - Quasiperiodic Spin--orbit Motion in Storage
Rings and a Rigorous Definition of Spin Tune*
J.A. Ellison, UNM, Albuquerque; D.P. Barber, K.
Heinemann, DESY, Hamburg
We present a rigorous discussion of the concept of spin
tune for integrable orbital motion in a storage ring. Spin
motion on the periodic closed orbit of a storage ring can
12 /52
be analyzed in terms of the Floquet theorem for equations
of motion with periodic parameters and the spin tune
emerges in a Floquet exponent as an extra frequency of
the system. To define spin tune on synchro--betatron
orbits we exploit the important concepts of
quasiperiodicity, the uniform precession frame and the
uniform precession rate. These allow a generalization of
the Floquet theorem whereby the
uniform precession rate appears in a Floquet exponent as
an extra frequency in the system in analogy with the case
of motion on the closed orbit. The spin tune is a uniform
precession rate obtained when certain conditions are
fulfilled. Having defined spin tune we define spin--orbit
resonance on synchro--betatron orbits and can then
examine its consequences. We give conditions (e.g.
where small divisors are controlled by applying a
Diophantine condition) for the existence of a spin tune
and illustrate with several examples. The formalism
suggests the use of Fourier analysis to "measure" spin
tune during computer simulations of spin motion on
synchro--betatron orbits.
*Work of J.E. supported by DOE contract DE-FG0399ER41104.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1638 - Applying the Birkhoff Ergodic Theorem to
Stroboscopic Averaging of Spin Fields and Liouville
Densities*
J.A. Ellison, UNM, Albuquerque; K. Heinemann, DESY,
Hamburg
A class of orbital systems with azimuth-periodic vector
fields and volume preserving flows is defined. Spin
degrees of freedom are added and for the resulting class
of spin-orbit motions spin fields are considered. By
performing
'stroboscopic" averaging, i.e. a ${\rm
Ces\grave{a}ro}$ summation of the spin field at an
increasing sequence of azimuth values, one gets, via
the Birkhoff Ergodic Theorem, polarization fields which
are periodic in the azimuthal variable. This fulfills the
main task of this paper in that it demonstrates that the
tracking algorithm, encoded in the program SPRINT and
used in the simulation of spin polarized storage rings, is
mathematically well-founded. Examples are considered
which illustrate certain points. The machinery developed
also works for "Liouville" densities associated with the
orbital dynamics. A tracking algorithm is derived which
provides periodic Liouville densities.
*Work of J.E. supported by DOE contract DE-FG0399ER41104.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
985 - Analytic Studies of the Long Range Beam-Beam
Tune Shifts and Chromaticities
B. Erdelyi, T. Sen, FNAL, Batavia
A formula was derived, which allows efficient analytical
evaluation of the long range beam-beam tune shifts with
amplitude and the chromaticities. It is assumed that the
beams are infinitely short, oppositely charged, and with
Gaussian transversal profile. The formula employs a quite
rapidly converging infinite sum, with convergence rate
depending only on the amplitudes, making it well suited
especially for the long range case. For a deeper
understanding of the beam-beam effects, the structure of
the formula is analyzed. It is shown that the tune shifts
change sign at certain values of the separation and/or
amplitude, and folds in the tune footprint are predicted.
Applications to the Tevatron are presented.
Type of presentation requested : Poster
Speaker :
Dr. T. Sen
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1862 - Orbital Motion in Storage Rings: Algebraical
Criteria of Stability and Localization
A. Fedorova, M. Zeitlin, IPME RAS, St. Petersburg
We consider orbital beam motion in storage rings with
and without control as variational problem with
constraints in arbitrary but finite rational n-pole
approximation. Set of reduced algebraical problems and
machinery of multiresolution representation in maximally
localized bases [1] allow to formulate algebraical and
computable criteria of stability and localization for
nonlinear beam motion. As example we consider
modeling and control for short-term dynamical aperture.
1.A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
43 - Observations of Beam-beam Effects in RHIC*
W. Fischer, J.M. Brennan, P. Cameron, R. Connolly, C.
Montag, S. Peggs, V. Ptitsyn, S. Tepikian, J. van Zeijts,
BNL, Upton, Long Island, New York
Beam-beam effects in RHIC were observed in operation
and in dedicated experiments with both gold ions and
protons. Observations include measurements of beambeam induced tune shifts, Schottky spectra with and
without beam-beam interaction, and lifetime and
emittance growth measurements with and without beambeam interaction. Transverse emittance growth due to
beam-beam interaction in conjunction with orbit
modulations is simulated. During ramps unequal radio
frequencies in the two rings cause the crossing points to
move longitudinally. Thus bunches experience beambeam interactions only in intervals and transverse tunes
are modulated. In proton operation, RHIC is the only
existing hadron collider in which strong-strong beambeam effects can be expected. Measurements of coherent
modes were attempted with proton beams.
13 /52
*Work supported by U.S. DOE under contract No DEAC02-98CH10886
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
46 - Measurements of Resonance Driving Terms in
RHIC*
W. Fischer, F. Pilat, BNL, Upton, Long Island, New York;
F. Schmidt, CERN, Geneva
Measured resonance driving terms may be used to correct
for nonlinear field errors in accelerators and storage rings.
This is especially interesting for local nonlinear
corrections in the interaction regions of machines like
RHIC and LHC. Measurements are presented that are
based on tune-by-turn data of the beam centroid with
different betatron amplitudes. Resonance strengths were
varied with a single sextupole corrector in one interaction
region.
*Work supported by U.S. DOE under contract No DEAC02-98CH10886
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
62 - Adiabatic Capture of Charged Particles in Islands
of Phase Space: A New Method for Multi-turn
Extraction
M. Giovannozzi, R. Cappi, CERN, Geneva
A new method for multi-turn extraction from a circular
particle accelerator is presented. It is based on adiabatic
capture of particles into islands of transverse phase space
generated by non-linear resonances. By appropriate use
of non-linear elements, such as sextupoles and octupoles,
stable islands can be created at small amplitude. By
inducing an appropriate slow variation of the linear tune,
particles can be captured inside these islands. This allows
the beam to be split into different smaller beamlets in the
transverse phase space. These beamlets can be finally
transported towards higher-amplitudes to prepare them for
extraction, performed by means of kicker and septum
magnets. Results of numerical simulations are presented
and discussed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
245 - Axisymmetric Vortices in Axisymmetric
Inhomogeneous Beams*
Y. Golub, MRI, Moscow
We analyzed localized vortices in non-neutral
inhomogeneous by density and velocity electron beams
propagating in vacuum along the external magnetic field.
These vortices distinguish from well-known vortices of
Larichev-Reznik or Reznik types, which used in [1]. New
types of vortex are obtained by new method of nonlinear
equations solution. That method distinguish from standard
Larichev-Reznik or Reznik method, which used in [1]. It
has been found new expression for electric field potential
of vortex in a wave frame. The expression is
axisymmetric in a wave frame. New vortices are the result
of external disturbances or the appearance and
development of instabilities like for example a diocotron
instability in hollow beams and a slipping-instability in
solid beams.
[1] Golub Yu.Ya., Nikulin M.G., Rozanov N.E. In:
Nonlinear world: IV Intern. Workshop on Nonlin. and
Turbul. Proc. in Phys., (ed. by V.G. Bar'yakhtar et all)
World Scientific Publishing Co. Pte. Ltd., Singapore,
1990, vol. 2, p.857
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
306 - Tolerances of the Spool Piece Correction System
for the LHC
M. Hayes, CERN, Geneva
The LHC main supeconducting dipoles are provided with
a spool piece correction system which is to be used to
correct locally the non-linear multipole errors b3, b4 and
b5. The tolerances of this
correction system to failures are discussed. Also discussed
are simple methods of ensuring they are set correctly
during commissioning.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
997 - Beam Tails in the PLS Storage Ring
E.-S. Kim, K.-M. Ha, D.-T. Kim, S.-J. Park, PAL, Pohang
Non-Gaussian transverse beam tails are investigated from
measurements of the beam lifetime in the PLS storage
ring. Gas-scattering lifetime and Touschek lifetime are
estimated from the measured beam lifetimes. The beam
tails are also compared with those that are obtained by a
simulation method.
Type of presentation requested : Poster
Speaker :
Eun-San Kim
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1037 - Study of Beam Lifetime in PLS Storage RIng
E.-S. Kim, PAL, Pohang
We investigate measurements and interpretation of the
beam lifetime at the PLS storage ring. The beam
lifetimes are observed under variations of several machine
and beam parameters such as gap height of insertion
devices, bunch filling pattern and coupling constant.
Type of presentation requested : Poster
Speaker :
Eun-San Kim
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
549 - Beam Dynamics Formation in Magnetic Field
E. Kotina, St. Petersburg State University, St. Petersburg
14 /52
In this paper methods of construction of magnetic fields
forming given beam dynamics are developed. We
consider this problem as the inverse problem of
determination of magnetic field by given motion of
charged particles. Different inverse problems of
electrodynamics have always been the subject of attention
of many researchers. Attempts to find approaches to the
solving of problems of such kind had been undertaken for
a long time. In particular, similar problems had been
considered in the works of G.A.Grinberg, A.R.Lucas,
B.Meltzer, V.T.Ovcharov, V.I.Zubov. In this paper
numerical-analytical method of finding of magnetic field
is developed. The investigated problem is reduced to the
solving of the Goursat problem for the quasi-linear system
of differential equations with partial derivation. To solve
this problem the method of characteristics and the Masso
method are developed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
809 - On the Possibility of Fast Charged Particles
Channeling in Dusting Crystals
N. Maksyuta, V. Vysotskii, National Taras Shevchenko
University of Kyiv, Kyiv
To obtain an effective short-wave radiation based on
channeling we could realize a positron-type regime for
electrons. This regime would cause an anomalous
dissipation of electron beam between hypothesis
crystallographic planes. So for the case of natural crystals
such regime doesn't work. However some artificial
structures would make true the possibility of positrontype regime channeling. Coulomb crystals named dusting
ones well studied in physics nowadays could suit best of
all. By-electrode layers tumed out to realize conditions for
periodic system origin and restrain. Its points of lattice
contain dusting particles of a fractal structure with great
negative charges. These charge values are determined by
a concentration and dusting particles dimensions. Besides
the possibility of being used for short-wave radiation in
dusting crystals they could be used as macroscopic
analogs of natural crystals suitable for orientation effects
study. We could propose a periodic structure which points
of lattice could accumulate electron neutral particles (e.g.
negative ions, surrounded by charged ones). It would
reveal new possibilities for electron orientational motion
realization.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1135 - Specific Design Peculiarities of Compact
Pproton Synchrotron for Hadron Therapy
A. Molodojentsev, KEK, Ibaraki-ken
The report presents study of specific design peculiarities
of the low-cycling proton synchrotron for hadron therapy,
in particular the space-charge effects of the low-energy
high-intensity proton beam and the nonlinear particle
motion caused by the magnetic field near the edge of the
magnets of the compact synchrotron. The space charge of
the beam can excite the high-order resonances without
any magnetic field imperfection that will lead to the
transverse emittance blow-up. From the other side, the
nonlinearities of the fringe fields become significant
especially in the case of large amplitude of the particles.
Combination of these effects in the case of the lowcycling compact synchrotron can limit the beam intensity
of the medical machine. To avoid it the proper choice of
main machine parameters should be based on accurate
analysis of these effects. The detailed study of the space
charge and fringe field effects for the compact proton
synchrotron is performed by ACCSIM and COSY
INFINITY codes. It is shown that the correct choice of
the "bare" betatron tunes can improve the dynamic
aperture of the synchrotron and minimize the blow-up of
the transverse emittances. The simulations are made for
the compact proton synchrotron designed by Hitachi, Ltd.
for the Proton Medical Center of the University of
Tsukuba.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1142 - Fringe Field Effects and Dynamic Aperture of
the 3 GeV JAERI-KEK Synchrotron
A. Molodojentsev, S. Machida, KEK, Ibaraki-ken
Fringe fields of synchrotron magnets induce a variety of
effects itself beginning from changing the linear
properties of the focusing structure. The pseudo-multipole
nonlinearities of the fringe fields become more significant
in the case of large amplitudes of the particles. As the
result these effects can change the dynamic aperture of
the synchrotron even without any magnetic field
imperfections. Accurate simulation of these effects
including amplitude dependent tune shift and chromaticity
are performed for the 3GeV synchrotron by using the
COSY INFINITY code. The fringe fields of the magnets
are presented by the Enge functions. Sensitivity of the
fringe field effects for different sets of the Enge
coefficients is tested. The dynamic aperture of the
synchrotron is estimated. The symplectic particle tracking
predicts regions of the betatron tunes near the design
values where the fringe field effects are most critical.
Optimization of the working point provides improving the
dynamic aperture of the synchrotron.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
851 - Measurements of Mechanical Triplet Vibrations
in RHIC*
C. Montag, R. Bonati, J.M. Brennan, J. Butler, P. Koello,
BNL, Upton, Long Island, New York
Mechanical vibraions of the RHIC interaction region
triplets has been identified as the dominant source of orbit
jitter for frequencies up to 20 Hz. Detailed
measurementws are reported that were performed in order
15 /52
to characterize these effects. We discuss its impact on
beam dynamics and possible cures.
* Work performed under the auspices of the U.S.
Department of Energy.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
855 - Modulated Beam-Beam Interactions as a
Possible Source of Emittance Growth in RHIC *
C. Montag, W. Fischer, T. Satogata, BNL, Upton, Long
Island, New York
During RHIC Au operations in mid-2001, low-frequency
(up to 20 Hz) beam orbit oscillations were present, with
amplitudes on the order of 10 percent of the transverse
beam size. These oscillations, created by mechanical
vibrations in triplet quadrupole assemblies, drive tune and
beam-beam offset modulations, and may drive transverse
emittance growth, thus degrading performance during
RHIC colliding beam stores. This paper presents the
current status and results of simulation studies to
determine associated growth mechanisms and rates.
* Work performed under the auspices of the U.S.
Department of Energy.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
coherent dipole oscillations or an emittance increase.
These two effects are studied using a strong-strong
multiparticle simulation model. The aim is to identify
possible limitations and to find procedures which
minimize possible detrimental effects.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
523 - Consequences of Beam-beam Interactions on the
Detection of Lepton Pairs Produced by Gammagamma Collisions in the LHC
B. Muratori, W. Herr, CERN, Geneva; D. Bocian, INP,
Cracow
The observation of electron-positron pairs produced in
gamma-gamma collision at the LHC can be used to
determine the luminosity of the proton proton collisions.
The observation of the leptons may be obscured by direct
and long range beam-beam effects and we have evaluated
these consequences in calculations and simulations to
estimate the feasibility of the method and possible
uncertainties.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
904 - Analysis of Multi-Turn Beam Position
Measurements in the CERN PS
A.-S. Mueller, M.E. Angoletta, M. Giovannozzi, M.
Martini, E. Metral, G. Metral, R. Steerenberg, CERN,
Geneva
The observation of betatron oscillations following a
deflection by a kicker pulse offers the possibility to study
various machine parameters. The decoherence and
recoherence of a bunch's centre-of-charge signal, for
example, is governed by chromaticity, momentum spread
and transverse non-linearities. The multi-turn acquisition
system of the CERN PS is able to store beam position
information of about 2000 turns. A careful analysis of
such data can be used to extract estimates of the
parameters involved, as well as to reconstruct the beam
dynamics in phase space. Experimental results are
compared to existing models.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
598 - Application of a New Class of Symplectic
Integrators to AcceleratorTracking
L. Nadolski, LBNL, Berkeley; J. Laskar, IMC-CNRS,
Paris
The dynamics of particle accelerator beams is commonly
described by a Hamiltonian of the form H=A+B where A
and B are integrable. Using Lie formalism, we give an
overview of a new class of symplectic integrator [1]
particularly well adapted when B is viewed as a
perturbation of A. These integrators with positive step
size can be constructed with a remainder of arbitrary
order n in A and order 2 in B. Moreover a corrector step
can be added to the integration scheme in many cases
such that the remainder becomes actually of order 4 in B.
A comparison with the fourth-order standard Forest and
Ruth's [2] is performed showing in general a one order
magnitude improvement in computation precision for the
same cost. The easy construction of these integrators is
sketched for the main magnetic elements of an electron
storage ring.
487 - Study of Offset Collisions and Beam Adjustment
in the LHC Using a Strong-Strong Simulation Model
B. Muratori, CERN, Geneva
The bunches of the two opposing beams in the LHC do
not always collide head-on. The beam-beam effects cause
a small, unavoidable separation under nominal
operational conditions. During the beam adjustment and
when the beams are brought into collision the beams are
separated by a significant fraction of the beam size. A
result of small beam separation can be the excitation of
[1] J. Laskar, P. Robutel, ``High order symplectic
integrators for perturbed Hamiltonian systems'', Celestial
Mechanics, vol. 80, pp. 39-62 (2001).
[2] E. Forest, R.D. Ruth, ``Fourth-order symplectic
integration'', Physica D, vol. 43(1), pp. 105-117 (1990).
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
16 /52
1619 - New Approach to Beam Dynamics
Optimization Problem
D. Ovsyannikov, SPbSU, St.Petersburg
In the works [1],[2] mathematical methods of
optimization of beam dynamics in accelerating and
focusing structures were developed. Optimization
problems of the charged particle beam dynamics were
treated as a control problem of trajectory ensemble of
dynamical system. In this paper another approach to
optimization problems is considered. It is based on the
investigation of special partial differential equations.
[1] Ovsyannikov D.A. (1996). “Mathematical
Methods of Optimization of Charged Partical Beams
Dynamics”. Proceedings of European Partical
Accelerator Conf., Barselona, Spain, Vol.2, p.1382-1384.
[2] Ovsyannikov D.A., Modeling and Optimization
Problems of Charged Particle Beams Dynamics,
Proceedings of the 4th European Control Conference,
Brussels, 1997, pp. 390-394.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1480 - The SNS Ring Dipole Magnetic Field Auality
I. Papaphilippou, J. Jackson, A. Jain, Y.-Y. Lee, W. Meng,
J. Wei, BNL, Upton, Long Island, New York
The large acceptance and compact size of the SNS ring
implies the use of short, large aperture dipole magnets
with significant end field errors, which can be locally
compensated with iron bumps and yoke chamfers. Special
care has to be taken to the accurate evaluation of the
fringe-field effect to beam dynamics. To this end, the ring
dipole magnetic field was modeled using 3D simulations
and compared with long and short coil measurements.
The impact of the dipole magnetic field quality to the
dynamics of the SNS ring is discussed and sorting
installation strategies are proposed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
742 - Dynamic Behavior of Charged Particle Beams in
Curvilinear Magnetic Field
Z. Parsa, BNL, Upton, Long Island, New York; V.
Zadorozhny, IK NASU, Ukraine
We study the stationary equilibrium orbits of compensate
charge particle beams in curvilinear magnetic filed.
Dynamics of charge particles in curvilinear coordinate
system and how to choose an electric field to construct
Brilluen's flow will be discussed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
948 - Linear and Nonlinear Corrections in the RHIC
Interaction Regions
F. Pilat, P. Cameron, V. Ptitsyn, BNL, Upton, Long
Island, New York; J.-P. Koutchouk, CERN, Geneva
A method has been developed to measure operationally
the linar and nonlinear effects of the interaction region
triplets, that gives access to the multipolar content
through the action kick, by applying closed orbit bumps
and analysing tune and orbit shifts. This technique has
been extensively tested and used during the RHIC
operations in 2001. Measurements were taken at 3
different interaction regions and for different focusing at
the interaction point. Nonlinear effects up to the
dodecapole have been measured as well as the effects of
linear, sextupolar and octupolar corrections. An analysis
package for the data processing has been developed that
through a precise fit of the experimental tune shift data
(measured by a phase lock loop technique to better than
0.00001 resolution) determines the multipole content of
an IR triplet. The experimental results have been
compared to a model of RHIC that includes the measured
magnet errors in the interaction region magnets.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1181 - Measurements of Tune Shifts with Amplitude at
the ESRF
A. Ropert, L. Farvacque, ESRF, Grenoble
Together with the reduction of third-order resonances
driving terms, the minimisation of tune shifts with
amplitude is an important lattice design issue for
synchrotron light sources. Since the beginning of ESRF
operation, the tuning of harmonic sextupoles has been
further refined to better match this objective and improve
machine performance. The experimental detuning with
amplitude has been determined from the analysis of turnby-turn BPM measurements for several sets of sextupoles
and compared with predictions from the model. The
limitations arising from the different contributions to
beam decoherence, from non-linear beam dynamics,... are
discussed.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
899 - On the Mechanisms of Particle Acceleration
K. Sadoyan, ARUS, Yerevan
A concept which rejects the existence of both magnetic
monopoles and electric charges in nature is proposed.
Electromagnetism is represented as a unified localized
process inside a material vacuum. The electric field
reflects dynamic aspects of the process while the
magnetic field - kinematical ones. As an attribute of
materiality of the vacuum it is considered the dissipative
character of the processes occurring in it. The
dissipativity of electromagnetic processes is evidenced by
the red-shift of spectral lines of the distant stars. The
Habble's constant characterizes the rate of photon
attenuation in the Universe. On the basis of equivalence
between the inertial and gravitational masses the relative
density of the material vacuum substance is established;
this density is by a factor of 2 x 10^13 greater than the
17 /52
nuclear density. The motion in the vacuum is described by
the laws of Continuum Mechanics. It is proved that the
maximum velocity of nuclear motion in the vacuum is
determined by the binding energy of nucleons in the
nucleus and its form-factor. The anomalously high
content of Li, Be and B nuclei in the cosmic rays is
considered as a result of effective acceleration of heavy
nuclei in strong gravitational fields with their subsequent
high-velocity collapse into high-energy light nuclei. The
mechanisms
of
particle
acceleration
in
the
electromagnetic and gravitational fields, as well as in the
nuclear processes are analyzed and possibilities for the
realisation of those mechanisms in the Earth's conditions
are considered.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1036 - Beam Decoherence due to Combination of
Wake Force and Nonlinearity in SPring-8 Storage
Ring
J. Schimizu, K. Soutome, M. Takao, Hitoshi Tanaka,
JASRI/SPring-8, Hyogo
Top-up operation is planned in the SPring-8 storage ring
to maintain the high brilliance of synchrotron radiation
during several bunch operation where beam lifetime is
extremely short due to Touschek effect. To realize the
top-up operation, we began to investigate the beam loss at
in-vacuum IDs during beam injection, but simulation
results could not explain the measured beam loss
evolution. To understand particle behavior from a beam
injection state to equilibrium state determined by
radiation effects, we have performed a simple experiment
to observe the beam decoherence, i.e., temporal variation
of the damping of beam coherent motion generated by a
single horizontal kicker. We found that the beam
decoherence much depends on chromaticities, the sign of
amplitude-dependent tune shift and beam current. This
suggests that short range wake force and nonlinearity of
ring parameters play an important role in the observed
phenomenon. By taking wake force into account, we
could see that simulation shows good agreements with the
experimental data. In this paper, we will show our present
analysis results on observed beam decoherence in the
SPring-8 storage ring.
Type of presentation requested : Poster
Speaker :
Dr. Hitoshi Tanaka
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
859 - Measurement of Resonance Driving Terms
F. Schmidt, M. Hayes, R. Tomas, CERN, Geneva
In 2001 a series of experiments have been performed at
the CERN SPS at an energy of 26 GeV to measure
resonance driving terms. Theory predicts that these terms
can be determined by harmonic analysis of BPM data
recorded after applying single kicks. This analysis works
equally well for linear and nonlinear diagnostics of
accelerators. Results of the experiments are presented,
including a direct measurement of resonance driving
terms and a comparison to the theory.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
360 - Some Features of Beam Dynamics in
Superconducting Linac Based on Quarter- and Halfwave Cavities
Y. Senichev, A. Bogdanov, A. Lehrach, R. Maier, R. Tölle,
E. Zaplatin, FZJ, Jülich
Super-conducting Injector LINAC for COSY has to
accelerate the protons and deuterium particles that differ
in mass by a factor of 2. There are two preferable types of
linear accelerator structures appropriate for this purpose:
the multi-gap structure with internal synchronization of
gaps, such as an Alvarez structure and the system with
external synchronizing of the different groups of
structures with few gaps, for instance the superconducting coaxial cavities. For our purpose the superconducting cavity is more appropriate. We consider two
options of linear accelerator based on the superconducting quarter- and half-wave resonators. In both
options the accelerator consists of two parts. In first and
second parts we use the resonators with 160 MHz and 320
MHz frequencies correspondingly. Simultaneously the
resonators are subdivided into families with the same
relative velocity. We optimize the number of resonators in
each group and each family. We discuss how to optimize
for protons and deuterium particles simultaneously. We
analyze the 6-dimensional beam dynamics in the real field
calculated by MAFIA. The quarter-wave cavity
technology is quite developed, but due to the dipole
component of magnetic and electrical fields the beam is
unstable in the transverse plane. We have developed the
special method to compensate this effect. In the half-wave
resonators such problem does not exist due to the field
symmetry. For the transverse plane we examine the
single, doublet and triplet systems. We investigate the
parametric resonance arising in the longitudinal plane due
to the drift space needed for the focusing elements and
determine the space limitation.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
970 - Beam-Based Global Correction of Nonlinear
Field Errors
J. Shi, University of Kansas, Lawrence
In the scheme of the global compensation of field errors
based on the minimization of nonlinearities in one-turn
maps, the nonlinear terms in the one-turn map are
minimized order-by-order with a few groups of correctors
and, consequently, the nonlinearity of the system can be
significantly reduced. One potential advantage of this
global correction scheme is that it allows an optimization
of the correction during the commissioning of an
accelerator if a one-turn map can be extracted from beam
18 /52
measurements. Such beam-based optimization is
especially important when there is significant uncertainty
in the magnet measurement or a significant change in the
multiples of magnets after a certain period of operation.
As a measured one-turn map always contains
experimental errors or uncertainties, the sensitivity of the
beam-based global compensation to the experimental
uncertainties in the measured one-turn maps was studied.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1586 - Strong-Strong Beam-Beam Simulation for LHC
J. Shi, L. Jin, University of Kansas, Lawrence, KS; W.
Herr, CERN, Geneva
Beam-beam effects in LHC were studied with including
multipole field errors in the lattice and head-on and longrange beam-beam interactions. The study was conducted
with tracking of one million particles over 100 thousand
turns by using the particle-in-cell method. The effect of
the wire-compensation of the long-range beam-beam
interactions and emittance growth due to head-on
collisions with possible offset were studied.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
195 - Orbit Hamiltonian, Synchrotron Oscillations and
Synchro-Betatron Coupling
T. Suzuki, KEK, Ibaraki-ken
A Hamiltonian formalism is developped for synchrotron
oscillations and synchro-betatron coupling. The orbit
length is chosen as an independent variable, and the
canonical variables are the arrival time and minus the
total energy. A standing-wave picture with a periodic
delta-function is shown to play an important role. We also
study the effect of changing magnetic fields (betatron
acceleration ) for synchrotron oscillations in the
Hamiltonian formalism. The present work is based on a
previous paper by the author (KEK 96-10 ), but the errors
are corrected and the contents are much extended.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
659 - Simple Calculation Method of Distributed
Momentum Acceptance along a Storage Ring
Hitoshi Tanaka, J. Schimizu, K. Soutome, M. Takao,
JASRI/SPring-8, Hyogo
Momentum acceptance (MA) plays an important role to
enlarge beam lifetime under the condition where electronelectron scattering is dominant in total beam loss. In this
case, MA is generally not constant along a storage ring
due to distributed energy dispersion. To optimize lattice
parameters, it is therefore important to calculate the
distributed MA and estimate the "effective MA" which
can be used as a typical value for the estimation of
Touschek lifetime. We then developed a simple
calculation method for the distributed MA by using first
order phase space distortion, nonlinear dispersion up to
4th order of dp/p, and dynamic aperture data at one point
in the ring. The calculated MA by this method well
explains the experimental data in the SPring-8 storage
ring. In this paper, we will present our calculation method
and comparison between the calculation and experimental
data.
Type of presentation requested : Poster
Speaker :
Dr. Hitoshi Tanaka
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
854 - Analysis of Nonlinear Resonances using an AC
Dipole in the CERN SPS
R. Tomas, F. Schmidt, CERN, Geneva; M. Bai, BNL,
Upton, Long Island, New York
AC dipoles in accelerators are used to excite coherent
betatron oscillations at a drive frequency close to the tune.
In principle these oscillations last arbitrarily long without
significant emittance growth if the AC dipole is
adiabatically turned on and off. Therefore the AC dipole
seems to be an adequate tool for non--linear diagnostics
provided the particle motion is well described in presence
of the AC dipole and nonlinearities. A powerful tool to
study these nonlinearities is the Normal Form technique.
In this article it is shown how this technique can be
generalized to include forced oscillations due to an AC
dipole. This new approach is applied to data from a recent
experiment at SPS in which non-linearities have been
studied in conjunction with AC dipole excitations.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
686 - Experimental Study on the Higher Order
Nonlinear Resonance at Taiwan Light Source
T.S. Ueng, J. Chen, K.-T. Hsu, K.-H. Hu, SRRC, Hsinchu
The higher order nonlinear resonances of transverse
betatron oscillation were studied experimentally at the
SRRC's storage ring. The turn-by-turn method and phase
space maps were used to analyze the experimental data.
The instantaneous tune was extracted to study the tune
variation from the different betatron amplitude and
different machine conditions. The linear coupling due to
the difference resonance at around the 6th order nonlinear
resonance has also been investigated.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1156 - Beam Injection and Longitudinal Emittance
Control in the JKJ 50 GeV Synchrotron
T. Uesugi, E. Ezura, Y. Hashimoto, Y. Mori, C. Ohmori,
A. Schnase, A. Takagi, M. Yoshii, KEK, Ibaraki-ken; F.
Tamura, M. Yamamoto, JAERI, Ibaraki-ken
In high intensity proton synchrotrons such as those of the
JAERI-KEK joint hadron(JKJ) project, it is important to
make peak space-charge density as low as possible. In
19 /52
the case of the 50 GeV synchrotron of the JKJ, it is
required that the longitudinal emittance of an injected
beam is enlarged more than 10 eVs before acceleration
keeping with the bunching factor more than 0.3, which
corresponds to the space-charge tune shift of 0.16. In this
paper, the scheme of the longitudinal beam manipulation
in the JKJ 50 GeV synchrotron is described with
simulation studies.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1211 - Non Linear Beam Dynamics for the Octupole
Compensated Lattice of DAFNE
C. Vaccarezza, D. Alesini, G. Benedetti, S. Bertolucci,
M.E. Biagini, C. Biscari, R. Boni, M. Boscolo, A. Clozza,
G. Delle Monache, G. Di Pirro, A. Drago, A. Gallo, A.
Ghigo, S. Guiducci, M. Incurvati, C. Ligi, F. Marcellini,
G. Mazzitelli, C. Milardi, L. Pellegrino, M.A. Preger, R.
Ricci, C. Sanelli, F. Sannibale, M. Serio, M. Serio, F.
Sgamma, A. Stecchi, A. Stella, M. Vescovi, M. Zobov,
INFN-LNF, Frascati (Roma); P. Raimondi, SLAC,
Stanford
Octupole magnets have been installed in DAFNE to
compensate an octupole-like component measured in the
wiggler magnets, providing a knob to control the tune
dependence on amplitude and Landau damping. DAFNE
operation with octupoles and comparison with simulations
are presented.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1610 - First-Order Averaging Principles for Maps
with Applications to Beam Dynamics in Particle
Accelerators *
M. Vogt, J.A. Ellison, UNM, Albuquerque; H.S. Dumas,
UC, Cincinnati
We extend the method of averaging at first order to
slowly evolving, discrete-time-dependent systems defined
by iterative maps. The validity of the averaging
approximation is demonstrated using a generalized Besjes
inequality. We study both cases of near-to-low-order
resonance and far-from-low-order-resonance. We apply
our results to localized perturbations of an otherwise
linear lattice. In particular we discuss the weak-strong
beam--beam effect.
Work supported by US D.O.E. grant DE-FG0399ER41104
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1681 - Explicit Symplectic Integrators for Modeling
3D Magnetic Field Elements
Y.K. Wu, DFELL, Durham
A variety of insertion devices (IDs), wigglers and
undulators, linearly or elliptically polarized, have become
widely used as high brightness radiation sources at
modern light source rings. In addition, long wigglers with
high magnetic fields have been proposed as radiation
damping sources for the next generation linear collider
damping rings. Like the insertion devices, the modeling of
the three-dimensional effects of the magnetic fringe fields
is critical for the future high energy accelerators including
future Hadron colliders and Neutrino Factory and Muon
Colliders with large aperture magnets. Since the early
1990's, the element-by-element tracking based on explicit
symplectic integrators has been successfully applied for
the design and optimization of third generation light
sources. However, the element-by-element tracking has
been limited to the magnetic elements with twodimensional fields, such as dipoles, quadrupoles, and
magnetic multipoles with an impulse boundary due to the
lack of explicit symplectic models for 3D magnetic
devices. This situation has been changed with our recent
work of explicit symplectic integrators for general 3D
magnetic field Hamiltonians. With this type of
integrators, particle motion in 3D magnetic devices can be
integrated as yet another magnetic element in a kick-code
at any given order. Consequently,
this explicit symplectic model allows the detailed analysis
of the beam dynamics in the next generation of
accelerators, from light source rings to high energy
physics rings, in which 3D field elements play a
significant role in beam dynamics.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1113 - Dynamic Aperture of the PoP-FFAG Proton
Synchrotron
M. Yoshimoto, T. Adachi, M. Aiba, S. Machida, Y. Mori,
R. Muramatsu, J. Nakano, C. Ohmori, I. Sakai, Y. Sato,
M. Sugaya, A. Takagi, R. Ueno, T. Yokoi, M. Yoshii, Y.
Yuasa, KEK, Ibaraki-ken; K. Koba, FNAL, Batavia
The Proof of Principle (PoP)-Fixed Field Alternating
Gradient (FFAG) synchrotron, which is the world first
FFAG proton synchrotron, was constructed at KEK, and
the various beam experiments have been carried out.
Among them, measurements of dynamic aperture is one
of the critical items. In the PoP-FFAG synchrotron, a
horizontal acceptance of more than 10000pi mm-mrad is
expected from beam tracking simulation, although the
magnetic field in the FFAG synchrotron intrinsically has
strong higher order components in order to satisfy the
zero chromaticity condition. The beam trajectories in the
horizontal phase space in the PoP-FFAG synchrotron are
measured to verify the large horizontal dynamic aperture
experimentally. We have developed a beam position
monitor, especially for that measurement, with which the
beam position and the angle can be obtained
simultaneously.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
20 /52
1514 - RMS Dynamics via Localized Modes
M. Zeitlin, A. Fedorova, IPME RAS, St. Petersburg
Computational methods based on the exact fast
convergent expansions in high-localized wavelet-like
bases are used for construction of solutions for a few
nonlinear rms-like (envelope) dynamical problems which
can be used for description and modeling important
features of collective type behaviour in momentum
approximation and are related to description of different
space-charge effects in high intensity transport systems in
accelerators and plasma physics problems. Our method is
based on the generalization of variational-wavelet
approach which allows to consider both polynomial and
rational type of nonlinearities without perturbations
or/and linearization [1]. All dynamical variables are
represented as expansions in the bases of maximally
localized modes and are parametrised by a number of
solutions of reduced standard algebraical problems which
can be solved by scalar or parallel algorithms. Best
convergence properties and minimal cost of algorithms
lead to saving CPU time and hdd space as on the level of
scalar as on the level of parallel algorithms inside.
1. A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005.
Type of presentation requested : Poster
Classification : [D02] Non-linear Dynamics Resonances, Tracking, Higher Order
1875 - Oscillations of Mismatched Beams in Fodo
Channels
O.A. Anderson, LBNL, Berkeley
Designers of accelerators for Heavy Ion Inertial Fusion
face various challenges because of the strong space
charge. Among other things, they need simple, accurate
tools for calculating quantities such as the phase advances
sigma0 and sigma given the lattice and beam parameters.
In conjuction with the KV beam model, the smooth
approximation [1] is often used. It is simple but not very
accurate in many cases. Although Struckmieir and Reiser
[2] showed that the stable oscillation frequencies of
unbalanced beams could be obtained accurately, they
actually used a hybrid approach where sigma0 and sigma
were given exactly in advance. Starting instead with
basic quantities?-quadrupole dimensions and field
strength, beam charge and emittance?-the smooth
approximation formulas give substantial errors (10% or
more). We previously described an integration method
[3] for matched beams that yields fairly simple third-order
formulas for sigma0, sigma, beam radius and ripple. Here
we extend the method to include small-amplitude
mismatch oscillations. We derive a simple modification
of the smooth approximation formulas and show that it
improves the accuracy of the predicted envelope
frequencies by a factor of five.
[1]
M. Reiser, Particle Accelerators 8, 167 (1978).
[2]
J. Struckmeier and M. Reiser, Particle
Accelerators 14, 227 (1984).
[3]
O.A. Anderson, Particle Accelerators 52, 133
(1996).
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1483 - Equilibrium Beam Distribution and Halo in the
LHC
R.W. Assmann, F. Schmidt, F. Zimmermann, CERN,
Geneva; M.-P. Zorzano, INTA, tbd
The equilibrium LHC beam distribution at large
amplitudes is a crucial input to the collimation and
machine protection design, as well as to background
studies. Its estimation requires a knowledge of the
diffusion rates at which beam particles are transported to
large transverse or longitudinal amplitudes. Important
known mechanisms of particle diffusion include
Touschek scattering, synchrotron radiation, intrabeam
scattering, the nonlinear motion due to the long- range
beam- beam collisions at top energy, persistent- current
field errors during injection and at the start of
acceleration, Coulomb scattering on residual gas, and
beam- gas bremsstrahlung. The expected contributions
from the different sources are summarized and the
corresponding equilibrium beam distribution is calculated.
The scattering process in the collimator jaws is included,
quantifying the overpopulation of the halo close to the
jaws due to "inward scattering". The result is compared to
simple estimates based on typical beam lifetimes in
existing proton rings.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
961 - Comparison of Space Charge Simulations by
Different Multi-particle Tracking Codes
J. Beebe-Wang, N.L. D'Imperio, A.U. Luccio, BNL,
Upton, Long Island, New York; S. Machida, KEK,
Ibaraki-ken
Space charge in high intensity beams is an important issue
in accelerator physics. Due to the complexity of the
problems, the most effective way of investigating its
effect is by computer simulations. In recent years, many
space charge simulation methods have been developed
and incorporated in various 2D or 3D multi-particle
tracking codes. It has become necessary to benchmark
these methods against each other, and against
experimental results. As a part of a global effort, we
present some comparison of the space charge calculations
done in the PIC codes ORBIT++, ORBIT and
SIMPSONS, with discussion of the relevant differences.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
676 - Longitudinal Beam Echos in Intense Ion Beams
O. Boine-Frankenheim, GSI, Darmstadt; A. Al-Khateeb,
Yarmouk University, Irbid, Jordan
21 /52
Temporal echos have already proven to be a sensitive
probe for diffusion processes in stored high energy
particle beams (see eg. [1,2]). If impedances can be
neglected the echo response is due to the free drifting
motion of the beam ions (ballistic echo). In order to
measure diffusion
rates in high phase space density beams at low and
intermediate energies (like eg. in the GSI cooler storge
ring ESR) the effect of the space charge impedance must
be included into the Vlasov-Fokker-Planck framework.
This requires a self-consistent analytical approach that
will be outlined.
The transition from the ballistic beam echo to the selfconsistent echo in a space charge dominated beam is
analyzed. As an application of the analytic theory we
determine and compare the numerical diffusion in
different self-consistent particle simulation schemes
(Particle-In-Cell and direct Vlasov) using longitudinal
beam echos
[1] L.K. Spentzouris, J.-F. Ostiguy, and P.L. Colestock,
Phys. Rev. Lett. 76, 620 (1996)
[2] O. Bruening, T. Linnecar, F. Ruggiero, W. Scandale,
E. Shaposhnikova, D. Stellfield, Proceedings of the EPAC
96, p.1332
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
382 - Emission and Control of H+ Ions near an
Electron-photon Conversion Target
A. Compant La Fontaine, D. Guilhem, J.-L. Lemaire, C.
Quine, CEA, Bruyeres-le-Chatel
A high-intensity relativistic electron beam is focused on a
tantalum target that converts the electrons into photons
via the bremsstrahlung process. The X-ray emission,
directed along the beam axis, is used for radiographic
purposes. The energy deposited by the beam focused on a
small spot size, causes local vaporisation of the target
and production of ions. A beam charge neutralisation then
occurs, cancelling the average radial electrical field.
Therefore, the beam pinches due to the remaining
azimuthal magnetic field. The ions are subsequently
accelerated downstream in the strong axial electric field
induced by the electron beam. Thus, the displacement of
the waist from the target along with the ions leads to an
increase of the spot size at the target and would result in a
degradation of the sharpness of the radiographic image.
The H+ light ions, issued from hydrogen atoms
contaminating the target, where identified on the PIVAIR
accelerator facility, with a time-of flight diagnostic placed
in front of the target. The H+ ions produced by ionisation
of the H atoms desorbed from the target by the electron
beam, is then calculated, and their transport is
implemented in the M2V Maxwell-Vlasov PIC code. In
this paper, we compare the experimental ionic current,
measured on the time-of-flight diagnostic with this abinitio model, by computing the H+ current collected on
this foil. The calculated mean velocity of the ions is in
agreement with the experimental result and the plateau of
the ion current is closed to the Child-Langmuir theoretical
limit. We also present the new self-biased target converter
designed in order to counteract the ionic motion. We
report on the successfull tests and beam size control along
the pulse.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
847 - A Deuteron Linac for Production of Medicine
Radioisotope Molybdenum-99
P. Demchenko, Y. Gussev, M. Shulika, KIPT, Kharkov
Production of a medicine radioisotope of molybdenum-99
using a high current deuteron linear accelerator had been
investigated. Molybdenum-99 is a generator of a
technetium-99m that is a very important radionuclide for
medicine diagnostics. It was shown that irradiation of a
natural molybdenum target by deuteron with energy of
15MeV and an average beam current of 1mA gave a
molybdenum-99 yield about 1.6Ci/h. As a result of
numerical simulation, a radio-frequency accelerating
channel of a high current deuteron linac had been
calculated. The accelerating channel consists of an ion
injector with output energy 100keV, an initial accelerating
section with radio-frequency quadrupole focusing (RFQ)
and output energy 2MeV, and two sections with
alternating phase focusing (APF) and output energy
15MeV. The sections with alternating phase focusing are
based on the interdigital H-type structures with drift
tubes. An operative frequency of the accelerating channel
is 152,5MHz. The details are given of a beam forming in
the ion injector, of a particle dynamics and the beam
phase space parameters in accelerating sections, and also
the features of a beam matching when the beam is moving
through the sections with different types of symmetry of
accelerating electric fields.
Type of presentation requested : Poster
Speaker :
Dr. P.O. Demchenko
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
881 - Beams Dynamics End to End Simulations in
IFMIF Linac
R. Duperrier, CEA, Gif-sur-Yvette; R. Ferdinand, N.
Pichoff, D. Uriot, CEA, Gif-sur-Yvette
The IFMIF project (International Fusion Material
Irradiation Facility) requests two linacs designed to
accelerate 125 mA CW deuteron beams up to 40 MeV.
After extraction and transport, the deuteron beams with
strong internal space charge forces have to be captured,
bunched, accelerated and transport to targets for the
production of high neutrons flux. This paper presents the
reference
design linac for this project. It is a combination of RFQ
and DTL. Beams dynamics end to end calculations with
errors studies and cavities design are detailed.
Type of presentation requested : Poster
22 /52
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1312 - Beams Dynamics End to End Simulations with
Errors Studies through the ESS linac
R. Duperrier, CEA, Gif-sur-Yvette; N. Pichoff, D. Uriot,
CEA, Gif-sur-Yvette
The ESS project (European Spallation Source) aims to
deliver high power beams for matter studies. Both protons
and H- have to be accelerated and guided to the different
spallation targets. Two 50 mA H- branches are funelled
with one 100 mA H+ beam at around 20 MeV. The Hfront end is constituted by a chopper lines between two
RFQs and DTLs. The H+ front end is composed by one
RFQ and one DTL. The two species are transported
through the same linac up to 1.334 GeV. This commpon
part is composed by SDTL and CCL from 20 to 185 MeV
and followed by a SCL (SuperConducting Linac) to reach
the final energy. This paper presents beams dynamics end
to end calculations with errors studies through the ESS
linac.
Type of presentation requested : Poster
Speaker :
Dr Nicolas PICHOFF
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1184 - Electron Cooling of Ion Beams with Large
Momentum Spread
H. Fadil, Y. Iwashita, A. Noda, T. Shirai, ICR, Kyoto; T.
Furukawa, Chiba University; M. Beutelspacher, M.
Grieser, MPI-K, Heidelberg; M. Muramatsu, K. Noda,
NIRS, Chiba City; S. Shibuya, SHI
A novel method for the reduction of electron cooling time
for an ion beam with large momentum spread has been
studied and experimentally tested at the TSR and HIMAC
rings. A constant external force is applied to the beam
using an induction accelerator, and the beam is rapidly
shifted toward the stable point of the cooling force. The
cooling time of a carbon ion beam (C6+ 73.3 MeV) with
momentum shift of 1% was measured at TSR. We have
observed a reduction from 2.5sec cooling time without
induction accelerator to 0.6sec when applying an
induction voltage of 0.4V. Also, we have investigated the
maximum limit of the induction accelerator voltage where
the ion beam becomes no longer captured by the electron
cooling force. The dependence of such a limit on the
electron density was measured using the HIMAC electron
cooler and a newly constructed induction accelerator for
Ar18+ ions.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1635 - Complex Emittance Dynamics in Space-Charge
DominatedHigh Brightness Beams
A. Fedorova, M. Zietlin, IPME RAS, St. Petersburg
We present numerical-analytical approach to nonlinear
rational envelope dynamics of space-charge dominated
high brightness beam systems, which can provide
understanding of the instability phenomena such as
emittance growth, mismatch, halo formation etc related to
complicated behaviour of underlying hidden nonlinear
modes outside of perturbative tori-like KAM regions. We
calculate the exact fast convergent representations for
solutions in high-localized wavelet-like bases functions,
which correspond to underlying hidden (coherent)
nonlinear eigenmodes [1]. The constructed solutions
correspond to the full multiresolution expansion in all
internal underlying scales and give expansion into slow
modes and fast oscillating modes. So, we give
contribution to dynamics as from coarse scales of
resolution as from finest ones to obtain all information
about complex dynamics of interaction of hidden
nonlinear eigenmodes, which leads to the understanding
of fully-developed instability processes. Because our
approach started from variational formulation we can
control evolution of instability on the pure algebraical
level of reduced algebraical system of equations. This
helps to control stability/unstability scenario of evolution
in parameters space. We demonstrate advantages of this
approach regarding perturbative ones.
1.A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
968 - Half-integer Resonance Crossing and Spacecharge Limit*
A.V. Fedotov, BNL, Upton, Long Island, New York; I.
Hofmann, GSI, Darmstadt
We study the influence of space charge on the crossing of
the second-order resonance and the associated spacecharge limit in high-intensity rings. Two-dimensional
simulation studies are compared with the envelope
models which agree in the finding of an increased
intensity limit due to the coherent frequency shift. We
also discuss the effect on realistic beams with multi-turn
injection painting, effects of coupling and high-order
resonances, and issues of the envelope instability in highintensity rings.
*SNS is managed by UT-Battelle, LLC, under contract
DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
974 - Exploring Transverse Beam Stability in the SNS
in the Presence of Space Charge*
A.V. Fedotov, M. Blaskiewicz, J. Wei, BNL, Upton, Long
Island, New York; V.V. Danilov, J.A. Holmes, A. Shishlo,
ORNL, Oak Ridge
23 /52
The highest possible intensity in the machine is typically
determined by the onset of coherent beam instabilities.
Understanding the contribution of various effects to the
damping and growth of such instabilities in the regime of
strong space charge is thus of crucial importance. In this
paper we explore transverse beam stability by numerical
simulations using recently implemented models of
transverse impedance and three-dimensional space
charge. Results are discussed with application to the SNS
accumulator ring.
*SNS is managed by UT-Battelle, LLC, under contract
DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
44 - Intra-beam Scattering Measurements in RHIC*
W. Fischer, R. Connolly, S. Tepikian, K. Zeno, J. van
Zeijts, BNL, Upton, Long Island, New York
RHIC in gold operation shows significant intra-beam
scattering due to the high charge state of the stored ions.
Intra-beam scattering leads to longitudinal and transverse
emittance growth. The longitudinal emittance growth
causes debunching in operation; the transverse emittance
growth contributes to the reduction of the beam and
luminosity lifetimes. Longitudinal and transverse growth
rates were measured with different intensities below and
above transition. Measured growth rates are compared
with computations.
*Work supported by U.S. DOE under contract No DEAC02-98CH10886
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
762 - Effect of Lattice Random Errors on a Space
Charge Dominated Beam
G. Franchetti, I. Hofmann, GSI, Darmstadt
The effect of random errors in linear accelerators raises
some fundamental questions on error propagation and
transformation into emittance growth due to the action of
space charge. In this paper we carry out a generic study of
this problem by using 2D computer simulation in a
periodic quadrupole channel. In the limit of no or very
weak space charge random focusing errors lead to the
well-known square root law of mismatch accumulation
with distance. In the presence of sufficiently strong space
charge the parametric (in some case also higher order)
resonances of particles with the mismatch motion lead to
a continuous damping of mismatch. This has the effect
that the average value of the rms emittance (over an error
ensemble) grows linearly with distance. Quantitative laws
on the rms emittance evolution as function of error
strength, and using a large number of error sets, are
presented.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
455 - The Electron Gun with Variable Beam Profile
for Optimization of Electron Cooling
A.V. Ivanov, A.V. Bubley, A.D. Goncharov, E.S.
Konstantinov, S.G. Konstantinov, A.M. Kryuchkov, V.M.
Panasyuk, V.V. Parkhomchuk, V.B. Reva, B.A. Skarbo,
B.M. Smirnov, B.N. Sukhina, M.A. Tiunov, M.N.
Zakhvatkin, BINP, Novosibirsk; X.D. Yang, IMP, Lanzhou
The electron cooling of the intensive ion beams shows the
problems connected with the development of the
instabilities inside cooled core of the beam. To avoid this,
the usage of the hollow electron beams was proposed. The
density of the electron beam at central part can be
decreased at many times without losses of the cooling of
whole ion beam. As results the recombination losses in
the core of the stored ion beam can be made less and the
intensive ion beam will interact with low intensive
electron beam that can decrease undesirable coherent
oscillations. The electron gun with the possibilities of the
variation of the electron beam profile was designed for
CSR cooler (IMP, China) and consists of the cathode,
control electrode and anode. The variation of the potential
sign of the control electrode permits to change the beam
profile from disk to ring in the cross-section. The gun
parameters were calculated using UltraSAM code. The
results of the microperveance and the electron beam
profiles measurements are presented. For the electron
beam profiles measurements the interaction of the
electron beam with crossed wire and with the residual gas
was used. The results are in good agreement with
calculations.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
626 - Stability Analysis of Intense Ion Beams in the
NIRS S-ring
V. Kapin, M. Kanazawa, T. Murakami, K. Noda, S.
Yamada, NIRS, Chiba City; E. Syresin, JINR, Dubna,
Moscow Region; S. Shibuya, Sumitomo Heavy Industries,
Tokyo
A small ring (S-ring) with circumference of 25 m has
been proposed at NIRS. It will produce an ion beam with
intensity higher 5 billions particle per second, the
injection energy of 6 MeV/u, energy of 1-28 MeV/u for
charge to mass ratio of 0.5 and bunch length of 10-1000
ns. The main peculiarities of S-ring are the low energy
after deceleration and the small circumference. A feature
of S-ring is a large relative length of the cooling section,
which occupies 3.6% of the ring circumference. This
value is 3-5 times higher than in the usual ion storage
rings. A maximum intensity of cooled ion beam can be
restricted by the ion beam instabilities. The application of
intense electron beam for fast cooling of ion beam in the
S-ring is limited so-called effect of electron heating. The
stability analysis includes the following effects: tune shift,
longitudinal and transverse beam instabilities, space
24 /52
charge effects in the electron cooling system, dipole
transverse instability due to interaction with ionization
electrons. Beam dynamics including space-charge effects
has been simulated using ACCSIM and WinAGILE
codes. Results of analytical estimations, stability analysis
and numerical simulations are presented.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
607 - Particle Diffusion due to Coulomb Scattering
V. Lebedev, S. Nagaitsev, FNAL, Batavia
Conventionally, the multiple and single particle scattering
in a storage ring are considered to be independent. Such
an approach is simple and often yields sufficiently
accurate results. Nevertheless there is a class of problems
where such an approach cannot produce correct results
and the single and multiple scattering need to be
considered together. This can be achieved by solving an
integro-differential equation for the particle distribution
function, which correctly treats particle coulomb
scattering. A derivation of the equation for the cases of
single- and two-dimensional betatron motion is presented
in the article. Numerical and analytical solutions for
important practical cases are also considered.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1559 - Longitudinal Cooling of A Strongly Magnetized
Electron Plasma
J. Lee, J. Cary, Center for Integrated Plasma Studies,
Boulder, CO
For a strongly magnetized plasma the small gyroradius
compared with the mean interparticle spacing makes the
energy exchange between perpendicular and parallel
almost vanish, so that the two energies are nearly
independently conserved. In this case, the thermodynamic
property of crystallization depends almost exclusively on
the parallel temperature, as the perpendicular degrees of
freedom act like internal degrees of freedom. On the
other hand, only the perpendicular degree of freedom is
well coupled (through synchrotron radiation) to the
outside. Thus, in the presence of a distant, lowtemperature wall, the perpendicular temperature
decreases, while the parallel temperature remains high,
and crystallization is not achieved. We propose to cause
crystallization through use of microwaves, which transfer
parallel energy to perpendicular. Our calculations show
that crystallization can be achieved in reasonable times (a
few hours) by this method.
Type of presentation requested : Poster
Speaker :
Professor. John Cary
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1579 - Analysis and Simulation of the CSR Induced
Modulational Instability
R. Li, TJNAF, Virginia
Recent analytical studies [1-3] and simulation [4]
indicated that coherent synchrotron radiation (CSR) could
induce microbunching instability for short electron
bunches passing through magnetic bending systems, such
as in the case of a bunch compression chicane or a storage
ring. In this paper, we present our simulation results on
the study of the CSR induced microbunching or
modulational instability, especially the dependence of the
growth rate on the design bunch distribution and on the
bunch transverse dynamics. We also describe our
simulation algorithm for the investigation of this
instability, and carry out analysis to explain the
simulation results.
*This work was supported by the U.S. Dept. of Energy
under Contract No. DE-AC05-84ER40150
[1] S. Heifets and G. Stupakov, Proceedings of 2001
Particle Accelerator Conference, 2001.
[2] E. L. Saldin, et al., Proceedings of the FEL2001
Conference, 2001.
[3] S. Heifets and G. Stupakov, SLAC-PUB-8988, 2001
[4] M. Borland, Proceeding.s of the 2001 Particle
Accelerator Conference, 2001
Type of presentation requested : Poster
Speaker :
Rui Li
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
843 - Space Charge Dynamics Simulated in 3-D in the
Code ORBIT
A.U. Luccio, J. Beebe-Wang, N.L. D'Imperio, BNL,
Upton, Long Island, New York
ORBIT is a PIC simulation code for beam dynamics in
synchrotrons, developed jointly by Oak Ridge and BNL.
Work is in progress at BNL to validate the code against
(1) physics, (2) machine experiments, and to (3) apply the
code to different types of lattice. This is coordinated with
similar work done at ORNL, that uses in some cases
different approaches, algorithms and coding, while the
basic formulation is the same.In the BNL implementation
(ORBIT++), 3D space charge is calculated by slicing the
beam in many longitudinal sections, with the calculations
done simultaneously in each slice with MPI on a parallel
computer. ORBIT uses distance along the ring as the
independent variable, so at each space charge 'node' the
beam is expanded to 'freeze' each macro particle in its
position at a given time. Image forces and currents on
walls are calculated by solving the Poisson/Ampere
equation with boundaries and then finding the impedances
(in the ORNL version the same calculations are done
using impedances as input). We have applied ORBIT++
to study a reference simple FODO machine, the Rapid
Cycling Medical Synchrotron (RCMS), the AGS Booster
and the AGS synchrotron. Results are discussed.
Type of presentation requested : Poster
25 /52
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1055 - Coherent Motion of a Bunched Beam and its
Resonances
S. Machida, KEK, Ibaraki-ken
It is now clear that resonances of a space-charge detuned
coasting beam in a circular accelerator is described by
coherent motions, not a single particle incoherent tune
[1,2]. For the lowest order resonance, the 2-dimensional
envelope equations predict that almost two times higher
tune shift (precisely speaking, it is 8/5) can be
accommodated than the one estimated by incoherent tune
shift formula. It is, however, not obvious that it is also
true for a bunched beam. Synchrotron oscillations may
destroy the coherence. Line density, which is assumed
constant in the 2-dimensional model, varys along the
bunch. We study coherent motion of a bunched beam with
multi-particle tracking code Simpsons.
[1] R. Baartman, AIP Conf. Proc. 448, (1998) p.56.
[2] S. Machida and M. Ikegami, ibid., p.73.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
184 - Beam Loading and Waveguide Buncher
Optimizing for High Current Relativistic Beam.
E. Masunov, MEPhI, Moscow
The problem of the bunching of a high current relativistic
electron beam in travelling-wave structure is studied. At a
high initial beam power the bunching efficiency is
determined by the beam itself in the waveguide structure,
rather than by the external rf fields. Optimization method
for beam phase-focusing action are suggested. There is a
detailed discussion of the final stage of the beam
interaction in the rf structure, in which an equilibrium is
established between the bunched beam and its own
microwave field. It is shown that the parameters of the
structure can be chosen to optimize the integrated
characteristics of the bunched electron beam.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
42 - Beam Dynamics Study of a Muon Cooling
Experiment with 200 MHz Cavities in the Framework
of the CERN Cooling Study
M. Migliorati, L. Palumbo, Dipartimento di Energetica,
Roma; K. Hanke, A.M. Lombardi, CERN, Geneva; F.
Tazzioli, C. Vaccarezza, INFN-LNF, Frascati (Roma)
Muon cooling is one of the building blocks for a Neutrino
Factory. It has the potential to increase the muon flux at
the detector of an order of magnitude. Different set-ups
for the experimental observation of cooling are proposed
and discussed by an international collaboration [MICE].
In this paper we present the results of the tracking studies
for a cooling experiment based on 200 MHz cavities with
superconducting solenoids and liquid hydrogen absorbers.
The cooling factor (i.e. the increase of the number of
particles in a given acceptance) achieved for a 200 MeV
muon beam passing through a system of 4 cavities at 7.6
MV/m is of the order of 10 %. This is believed to be well
within the capability of the measurement apparatus and
sufficient to gather important information for the final
design of a full-scale cooling channel.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
505 - Thin Foil Physical Effects on the Transport of an
Intense Relativistic Electron Beam
O. Mouton, D. Guilhem, CEA, Bruyères-le-Châtel
While it crosses a perpendicular thin foil, an electron
beam suffers a well known emittance growth due to the
Coulomb scattering mechanism which alters the
propagation of the beam. It also suffers a foil focusing
effect caused by the beam induced foil charges. We have
implemented these effects in an envelope simulation code
TRAJENV capable of studying the beam propagation
along transport lines. The moments are calculated in two
different manners: the first one via a numerical integration
and in the second one analytical solutions are used.
Simulations results are compared to experimental
measurements for relativistic electron beams (6 MeV, 3
kA) propagating through solenoidal chanels.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1363 - Flip-Flop Phenomenon Observation at VEPP2M
I. Nesterenko, P. Ivanov, A. Valishev, BINP, Novosibirsk
In this paper the experimental studies of flip-flop
phenomenon at two different excitation modes for vertical
emittances of e+e- colliding beams are presented. This
experimental data was obtained at VEPP-2M in summer,
2000. A comparison of the phenomenological model with
the experimental data is given. It is shown that a nonresonant generation of the vertical emittances (by means
of excitation of the vertical dispertion in bending magnets
such as to exclude the dependence of the natural vertical
emittance on the linear optics distortion due to a beambeam interaction) permits to increase significantly the
blowup threshold in comparison with the mode when the
emittances are determined by coupling of vertical and
horizontal betatron oscillations and by vicinity of the
betatron tunes to coupling resonance.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
289 - Design of the ACR Electron Cooler at RIKEN
M. Nishiura, T. Katayama, Toshiya Tanabe, RIKEN,
Saitama; A. Sidorin, JINR, Dubna, Moscow Region; I.
Watanabe, TOSHIBA
The radioisotope beam factory (RIBF) is under
construction at RIKEN. In the RIBF, multi-use
experimental storage rings (MUSES) consists of an
26 /52
accumulator cooler ring (ACR) and an electron-RI beam
collider (e-RI Collider). The ACR is equipped with an
electron cooler (EC). The 3 dimensional calculations of
magnetic fields and beam trajectories are carried out in
order to obtain better configuration in the gun and the
toroidal section of the ACR-EC. The cooling time is
calculated using these parameters.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
639 - Electron Cooling Experiment at HIMAC
synchrotron
K. Noda, T. Honma, M. Muramatsu, NIRS, Chiba City; T.
Furukawa, Chiba University, Chiba; S. Shibuya, SHI,
Tokyo
One of the objectives of HIMAC is to develop new
technologies in heavy-ion therapy and related basic and
applied research. For the purpose, it is very important to
improve beam property and enhance capability of
handling it. The electron-cooling method can provide
high-intensity or high-quality beams by cool stacking and
by its strong phase-space compression. The aim of our
study is to apply those techniques of accelerator physics
to medical and other fields. These techniques will lead to
the following: (1) an increase in the intensities of
positron-emitter beams for the ion range measurements
and of heavier ions, such as Fe and Ni, (2) micro-beam
probe for the cellular radiation-response, and (3) shortbunched beams for time-resolving measurements. At
HIMAC synchrotron, thus, electron-cooling experiments
have been carried out. In the transverse coolingexperiments, a cooling time and an equilibrium emittance
at horizontal direction were measured and an intrabeam
scattering was also measured. Beam intensity was
increased by one order through the cool-stacking method.
Beam bunch was compressed from around 400 ns to 40 ns
by the electron cooling. The experimental results will be
presented.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
432 - Parametric Resonances in Intense Hadron
Beams
H. Okamoto, Hiroshima University, Higashi-Hiroshima;
S. Machida, K. Yokoya, KEK, Ibaraki-ken
This paper presents several interesting results of resonant
beam instability induced by the periodic nature of external
focusing force. Firstly, an eigenvalue equation that
determines the frequencies of collective oscillation modes
in a one-dimensional beam is given by solving the
Vlasov-Poisson equations. Approximate formulae for the
resonance stopbands and growth rates are derived from
the eigenvalue equation. It is shown that the beam
becomes unstable not only when a coherent tune is close
to an integer but also when it is near a half integer.
Secondly, a general Hamiltonian formalism is constructed
for the study of two-dimensional space-charge-dominated
beams in circular accelerators. The theory suggests the
possibility of a novel resonant instability driven by
momentum dispersion and space charge. The particle-incell simulation technique is employed to confirm the
existence of a "dispersive resonance" stopband.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
433 - A New Experimental Approach to Space-charge
Effects
H. Okamoto, K. Ito, A. Ogata, R. Takai, Y. Wada,
Hiroshima University, Higashi-Hiroshima
In recent papers[1], we proposed a novel experimental
approach to investigate various collective effects in spacecharge-dominated beams. It was demonstrated that either
a radio-frequency quadrupole trap or a solenoidal trap
could reproduce nonlinear collective processes equivalent
to those in a beam transport channel. In the present paper,
we outline the essence of the idea, showing typical trap
configurations for beam-physics applications. We also
briefly discuss possible trap experiments that greatly
deepen our current understandings of collective beam
instabilities including coherent resonances and halo
formation.
[1]. H. Okamoto, Hiroshima University Preprint HUBP01/98 (1998); H. Okamoto and H. Tanaka, Nucl. Instr.
Meth. A437 (1999) 178.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
434 - On the Maintenance Condition of a Crystalline
Beam
H. Okamoto, K. Okabe, Y. Yuri, Hiroshima University,
Higashi-Hiroshima
It is widely believed that the so-called "maintenance
condition" must be satisfied to achieve beam
crystallization in a cooler storage ring. The condition
requires the ring lattice to have a betatron phase advance
below about 127 degrees per single superperiod[1]. In the
present work, we show that this condition is not sufficient
in general situations. Systematic multi-particle
simulations and analytic studies suggest that the phase
advance per lattice period should be lower than 90
degrees in order to totally avoid half-integer resonance
crossing during the cooling process.
[1]. J. Wei, X.-P. Li, and A. M. Sessler, Phys. Rev. Lett.
73 (1994) 3089; J. Wei, H. Okamoto, and A. M. Sessler,
Phys. Rev. Lett. 80 (1998) 2606.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
586 - Luminosity and Energy Resolution in e+eColliding Rings
S. Petracca, University of Sannio, Benevento; K. Hirata,
The Graduate University for Advanced Studies, Hayama
27 /52
Luminosity is one of the key concepts for accelerator
design. When the design target is a narrow energy peak,
the collision energy resolution becomes more relevant.
In this paper we give a fairly accurate expressions for
luminosity and energy resolution based on the Gaussian
approximation of the beam distribution functions[1]. All
kind of couplings are considered.
Work sponsored in part by INFN and by EC through a
grant to S.P.
[1] S.Petracca and K. Hirata, Jpn. J. Appl. Phys. 2001,
vol. 40,p.5123-5129.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
973 - Small Isochronous Ring Project at NSCL*
E. Pozdeyev, F. Marti, J.A. Rodriguez, R.C. York, NSCL,
East Lansing
The Small Isochronous Ring (SIR) is under development
at National Superconducting Cyclotron Laboratory
(NSCL) at Michigan State University (MSU). The main
objective of the project is the experimental study of space
charge effects in the isochronous regime. The ring is a
small-scale experiment that requires low beam intensities
to simulate the dynamics of intense beams in large-scale
accelerators. The important issues to be addressed by the
ring are the space charge induced vortex motion specific
to the isochronous regime, the longitudinal break-up of
long bunches, formation of the self-consistent stable
charge distribution by short bunches, and formation of
weak beam tails and beam halo. This paper reports the
status of the project and describes the design of major ring
systems.
* Work supported by the NSF Grant # PHY 0110253 and
the US Department of Energy Contract # DE-FG0299ER41118
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
975 - Computer Simulations of the Beam Dynamics in
the Small Isochronous Ring*
E. Pozdeyev, J.A. Rodriguez, NSCL, East Lansing
A Small Isochronous Ring (SIR), whose main objective is
the experimental study of the space charge effects in the
isochronous regime, is under development at National
Superconducting Cyclotron Laboratory (NSCL) at
Michigan State University (MSU). To study the beam
dynamics in the ring we tracked particle trajectories in a
realistic magnetic field generated by TOSCA. The singleparticle tracking shows that the horizontal and vertical
dynamic apertures of the ring are 8 cm and 5 cm
respectively at the injection energy. With the inclusion of
an energy spread of +-5%, the dynamic aperture is still
greater than 4 cm. To simulate the multi-particle beam
dynamics in the ring, we have developed a threedimensional PIC code that accurately calculates particle
trajectories in a specified magnetic field. A field solver
based on Fast Fourier Transformations calculates the
space charge field of the beam. Multi-particle simulations
show that the energy spread within a bunch circulating in
the ring grows from 0 to +-3% in 20 turns. In addition, the
bunch breaks into a set of small round clusters. Detailed
investigation reveals that particles within each cluster are
involved in a vortex motion induced by the space charge
force.
* Work supported by the NSF Grant No. PHY 0110253
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
967 - Injection Line of the Small Isochronous Ring*
J.A. Rodriguez, F. Marti, E. Pozdeyev, NSCL, East
Lansing
The Small Isochronous Ring (SIR), under development at
National Superconducting Cyclotron Laboratory (NSCL)
at Michigan State University (MSU), is a ring whose main
purpose is the study of longitudinal space charge effects
[1]. This paper describes the SIR injection line.
Descriptions of the ion source, einzel lenses, bending
magnet, diagnostics, chopper, and ring injection inflector
plates are given.
Single particle beam dynamics
simulations performed using SIMION and TOSCA are
detailed. Experimental results are provided and compared
to simulations.
*Work supported by NSF Grant # PHY-0110253 and U.S.
Department of Energy Contract # DE-FG02-99ER41118
[1] E. Pozdeyev et al, Small Isochronous Ring Project at
NSCL, these proceedings
Type of presentation requested : Poster
Speaker :
Dr. E. Pozdeyev
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1366 - Simulation Study of Beam Compression by
Barrier Bucket for ACR at RIKEN MUSES
A. Sakumi, RIKEN, Saitama; T. Katayama, T. Takeuchi,
CNS, Saitama; P. Zenkevitch, ITEP, Moscow
MUSES-ACR is designed to make accumulated and
cooled beam for not only the radioactive isotope ion
beams, but also intense primary ion beams. We proposed
the barrier bucket method as a beam bunching system in
ACR. We calculated the dynamics of the accumulating
beam in the ACR are compressed by barrier bucket.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
926 - Beam Dynamics Design of a Superconducting
175 MHz CH-Linac for IFMIF
A. Sauer, H. Deitinghoff, H. Klein, U. Ratzinger, R. Tiede,
IAP, Frankfurt-am-Main; R. Eichhorn, GSI, Darmstadt
In the IFMIF project the generation of a 125 mA, 40 MeV
D+ beam is required to produce very high neutron fluxes
from a liquid Li target to test possible wall materials for
inertial fusion chambers. The linac design consists of a
RFQ accelerator as first part (0.100 - 5 MeV) followed by
28 /52
a drift tube linac from 5 to 40 MeV. The required cw
operation favours a superconducting approach with
shorter length, high efficiency and larger aperture, which
gives a higher safety margin against possible particle
losses and resulting structure activation. One well suited
candidate may be the CH-structure, which combines high
acceleration efficiency with comparatively small
geometrical dimensions. In a first attempt a beam
dynamics design have been studied: a combination of a
normal-conducting
IH-cavity
followed
by
a
superconducting 175 MHz CH-section, which fulfills all
IFMIF requirements. The DTL length is about 10 m only.
Results of multiparticle simulations show very good beam
behaviour and will be presented and discussed together
with the main structure parameters.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1779 - Kinetic Theory of Periodic Holes in Debunched
Particle Beams*
H. Schamel, J.-M. Griessmeier, University of Bayreuth,
Bayreuth; R. Fedele, Universita Federico II and INFN,
Napoli
A self-consistent theory of periodic hole structures in
coasting beams in synchrotrons and storage rings is
presented, extending the theory on localized holes. The
analysis reveals new intrinsic nonlinear modes which owe
their existence to a deficiency of particles trapped in the
self-sustained potential well, showing up as notches in the
thermal range of the distribution function. It is hence the
full set of Vlasov-Poisson equations which is invoked;
linearized treatments as well their nonlinear extensions
fundamentally fail to cope with this strongly
nonthermodynamic phenomenon. Qualitative agreement
[1] with the holes recently found at the CERN Proton
Synchrotron Booster [2] is shown.
* This work is supported by DAAD (Deutscher
Akademischer Austauschdienst) and CRUI (Conferenza
dei Rettori delle Universita Italiane) within the research
program "Vigoni" between the University of Bayreuth
and the University Federico II of Napoli.
[1] To appear in Phys. Rev. ST Accel. Beams (2002)
[2] S. Koscielniak, S. Hancock and M. Lindroos, Phys.
Rev. ST Accel. Beams 4,044201 (2001)
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1223 - An Electron Cooler Design for the S-ring at
NIRS
S. Shibuya, K. Noda, S. Yamada, NIRS, Chiba City; E.
Syresin, JINR, Dubna, Moscow Region; T. Tachikawa,
Sumitomo Heavy Industries, LTD.
A small synchrotron project for heavy ions has been
started at NIRS. The small synchrotron (S-ring), whose
circumference is less than 25-m has been designed to
supply heavy-ion beams with a charge to mass ratio of 1/2
ranging of energy from 1 to 28-MeV/n. The project will
be presented in this conference*. In this synchrotron, an
electron cooler is installed to be able to deliver a low
emittance beam at any energy range, a high intensity
beam using cooling and stacking technique, and deliver a
short-bunched beam using cooling and phase rotation
technique. The cooler consists of two toloid magnets with
a radius of 650-mm, a main solenoid magnet with a length
of 900-mm, an electron gun with high perveance, and
highly efficient collector system. A magnetic field of the
main solenoid is 0.05-T, and the maximum expansion
ratio is around 10. A design of the cooler are presented.
* K.Noda et.al, "S-ring project at NIRS", this conference.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1038 - Hamiltonian Dynamics of Intense Beams in a
Nonlinear Focusing Channel
K. Sonnad, J. Cary, CIPS, Boulder
The continuous focusing model for high intensity beams
shows that nonlinear terms in the external focusing induce
damping of the envelope oscillations. We propose that
this could be applied to reduce beam halos. We then
derive a Hamiltonian that is averaged over a lattice period
for an intense beam under the influence of quadrapole and
octupole focusing terms. This analysis is for a thin,
unbunched beam and assumes that the lattice period is
much smaller than the period of the envelope oscillation.
This averaging procedure reduces the computation time
by eliminating the rapid time scale from the problem,
while retaining the essential physics.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1093 - Cure for a Transverse Instability during
Electron-Cooling Bunching
M. Takanaka, RIKEN, Saitama
We have studied characteristics of electron-cooled
bunched ion beams using a multiparticle tracking
simulation. During electron-cooling bunching, the beams
become space-charge dominated and meet a transverse
instability of which the source is the toroid field at the
electron-cooling section. We check if a set of skew
quadrupole magnets are an effective cure for the
instability.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1102 - Halo-formation and beam loss in the 3GeV
Ring of the Joint Project
K. Takayama, T. Adachi, S. Igarashi, S. Machida, Y.
Shimosaki, M. Shirakata, KEK, Ibaraki-ken; F. Noda, T.
Shigaki, JAERI, Tokai; N. Tani, SOKENDAI, Tsukuba
A systematic study on the halo-formation predicted in the
3GeV Booster Ring for the Joint Project has been
performed. Orbits of interacting particles are examined
by utilizing three independently developed computer
29 /52
codes of ACCSIM, SIMPSONS, and PATRASH. Selffields, higher multipole fields in the lattice magnets as
well as sextupole fields for chromaticity correction are
included in the tracking simulations. For a typical
example, driving mechanisms of halo-formation are
manifested. Absolute sizes of the halo are given as a
function of the beam intensity for a set of possible
machine parameters. The size tells us an achievable beam
intensity under the best machine-condition, which would
allow hands-on-maintenance.
Type of presentation requested : Poster
Speaker :
Dr. Susumu Igarashi
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1609 - Comparison between the Predictions and
Mmeasurements for the Beam Gas Interactions during
the Last Gold and Proton Runs in RHIC
D. Trbojevic, W. Fischer, H.-C. Hseuh, W.W. MacKay,
S.Y. Zhang, BNL, Upton, Long Island, New York
The last gold-gold and polarized proton-proton collision
runs were performed at energies of 100 GeV/nucleon. The
beam gas interactions in RHIC are very important for the
beam lifetime in RHIC. This is a report where the
pressure data differences between the beams on and
beams off at injection and at the 100 GeV/nucleon energy
are compared with predictions for the beam gas
interaction and beam lifetime for both gold and proton
beams.
[1] work supported under auspices of the U.S. Department
of Energy
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
977 - A High-Intensity Highly-Polarized Electron
Beam for High-Energy Physics*
J.L. Turner, A. Brachmann, J.E. Clendenin, F.-J. Decker,
D.-A. Luh, T. Maruyama, M.B. Woods, SLAC, Stanford
A new high-energy parity violation (PV) experiment at
SLAC as well as particle-physics experiments using
future e+e- colliders (such as NLC) operating at energies
above the scale of unification of the electromagnetic and
weak interactions require a highly-polarized electron
beam with intensity requirements previously unachievable
due to a surface charge limit effect at the cathode of the
polarized
electron
source.
Using
a
GaAs(0.95)P(0.05)/GaAs(0.66)P(0.34)
single-layer
photocathode with high surface doping that was recently
developed at SLAC as part of the NLC R&D effort [1], a
beam with >2x10^12 e- per 100 ns of pulse length (and up
to 3 A/cm^2) has been produced at the electron source of
the SLAC 3-km linac, limited only by the available laser
energy. This is considerably more charge per unit pulse
length than required for the NLC macropulse. The
polarization measured in the laboratory is ~80%. The
present PV experiment (E-158) at SLAC requires
8x10^11 e- in a 370 ns pulse (350 mA). Consequently
there is sufficient head room to shape the pulse temporal
profile to allow the necessary energy compensation for
the linac beam loading to limit the energy spread at 48.7
GeV to ~0.3% rms. The intensity stability required for
stable machine operation is determined by the source laser
stability. After recent improvements [2], the SLAC-built
flashlamp-pumped Ti:sapphire laser now has an energy
stability of ~1% rms. Temporal pulse shaping is
performed on the laser beam using an improved pulse
shaper. Details of the beam generation, energy
compensation, and linac performance recently achieved
for E-158 will be discussed.
*Work supported by Department of Energy contract DEAC03-76SF00515.
[1] T. Maruyama et al., "Overcoming the surface-chargelimit using high-gradient-doped strained photocathodes,"
to be submitted for publication.
[2] R. Alley et al., "SLAC's polarized electron source
laser system for the E-158 parity violation experiment," to
be submitted for publication.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
111 - Renormalization Group Approach to the BeamBeam Interaction in Circular Colliders
S. Tzenov, PPPL, Princeton
Building on the Renormalization Group (RG) method the
beam-beam interaction in circular colliders is studied. A
regularized symplectic RG beam-beam map, that
describes successfully the long-time asymptotic behavior
of the original system has been obtained. The integral of
motion possessed by the regularized RG map has been
used to construct the invariant phase space density
(stationary distribution function), and a set of coupled
nonlinear integral equations for the distributions of the
two colliding beams has been derived.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
406 - Solitary Waves in an Intense Beam Propagating
Through a Periodic Focusing Field*
S. Tzenov, PPPL, Princeton; R. Davidson, PPPL,
Princeton, New Jersey
Based on the Vlasov-Maxwell equations describing the
self-consistent nonlinear beam dynamics and collective
processes, the evolution of an intense sheet beam
propagating through a periodic focusing field has been
studied. In an earlier paper [1] it has been shown that in
the case of a beam with uniform phase space density the
Vlasov-Maxwell equations can be replaced exactly by the
macroscopic warm fluid-Maxwell equations with a tripleadiabatic pressure law. In this paper we demonstrate that
starting from the macroscopic fluid-Maxwell equations a
nonlinear Schroedinger equation for the slowly-varying
wave amplitude (or a set of coupled nonlinear
Schroedinger equations for the wave amplitudes in the
case of multi-wave interaction) can be derived. Properties
30 /52
of the nonlinear Schroedinger equation are discussed,
together with the role of solitons in halo formation in
intense particle beams.
* Research supported by the US Department of Energy.
[1] Ronald C. Davidson, Hong Qin and Stephan I.
Tzenov, ``Kinetic Description of Intense Beam
Propagation Through a Periodic Focusing Field for
Uniform Phase Space Density'', to be submitted for
publication (2002).
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1520 - A New Model for the Strong--Strong Beam-Beam Interaction *
M. Vogt, J.A. Ellison, UNM, Albuquerque
The Strong-Strong Beam-Beam is studied in the
framework of maps with a "Kick-Rotate" model in 4-D
phase space. The classical method of averaging is applied
to derive an approximate map which is equivalent to a
flow within the averaging approximation. This flow leads
to an averaged Vlasov equation (AVE). The power of this
approach is evidenced by the fact that the AVE has exact
equilibria and the associated linearized equations have
uncoupled azimuthal Fourier modes. In the usual way,
the Fourier mode equations lead to a Fredholm integral
equation of the third kind. This is a generalization of the
2-D case presented at the recent Beam-Beam Workshop at
Fermilab 2001. Comparison with simulations of the exact
system will be presented.
* Work supported by US D.O.E. grant DE-FG0399ER41104
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1532 - Simulations for RHIC Beam-Beam
Experiments *
M. Vogt, J.A. Ellison, UNM, Albuquerque; T. Sen, FNAL,
Batavia
A recent experiment at RHIC examined the coherent
dipole modes for hadron bunches in collision.
We have simulated the collective beam-beam effect in
RHIC selfconsistently in 4-D (transverse) phase space.
Compared to standard Monte-Carlo methods our methods
improve the sampling of the halo regions of phase space.
We compare our simulations with the experimental
results.
* Work supported by US D.O.E. grant DE-FG0399ER41104 and the US VHLC project
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1272 - Electron Beam Generation in Multicathode
Secondary-emission Systems
V. Zakutin, N. Ajzatsky, V. Boriskin, A. Dovbnya, V.
Kushnir, V. Mitrochenko, N. Reshetnyak, V. Romas'ko,
KIPT, Kharkov; M. Krasnogolovets, T. Semenets, Y.
Volkolupov, KhNURE, Kharkov
The paper reports the results of investigations into the
electron beam generation by a secondary-emission
cathode system in crossed magnetic and azimuthdissimilar electric fields. In the first case, the system
under study consisted of pin anodes and pin cathodes. The
anodes were arranged at the intersection of the axes
forming squares in the plane perpendicular to the pins,
and the secondary-emission cathodes were placed
between them at the intersection of diagonals that formed
a set of cells. At a cathode diameter of 5 mm, a magnetic
field strength of 2.5 to 3.5 kOe, and a voltage amplitude
of 45 kV, the current of a tubular electron beam in a
single cell was between 12 and 14 A. In a four-cell
system, at a voltage amplitude of 28 kV and a magnetic
field strength of 2200 Oe, the beam current was measured
to be 22 A. In the second case, the system under study
included the anodes in the form of two coaxially arranged
cylinders and eight secondary-emission pin cathodes
evenly distributed around a circle in the gap between the
anodes. At a voltage amplitude of 34 kV and a magnetic
field strength of ~2600 Oe, the total beam current was
equal to 35 A.
Type of presentation requested : Poster
Speaker :
Prof. A.Dovbnya
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
1232 - Fast Calculation Methods in Collective
Dynamical Models of Beam/Plasma Physics
M. Zeitlin, A. Fedorova, IPME RAS, St. Petersburg
We consider applications of numerical--analytical
technique based on the methods of local nonlinear
harmonic analysis to nonlinear collective models of
beam/plasma physics, e.g. some forms of VlasovMaxwell-Poisson equations related to modeling of
propagation of intense charged particle beams in highintensity accelerators and transport systems [1]. In our
approach we use fast convergent
variational-wavelet representations for solutions, which
allows to consider polynomial and rational type of
nonlinearities. The solutions are represented via the
multiscale decomposition in nonlinear high-localized
eigenmodes (generalized Gluckstern modes), which
corresponds to the full multiresolution expansion in all
underlying hidden time/space or phase space scales. In
contrast with different approaches we do not use
perturbation technique or linearization procedures. Fast
scalar/parallel modeling demonstrates appearance of highlocalized coherent structures in spatially--extended
stochastic systems with complex collective behaviour.
1.A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
31 /52
135 - Control of Beam Space Charge Redistribution
and Emittance Growth
Y. Zuev, NIIEFA, St. Petersburg
A charged beam in confining fields tends to an
equilibrium configuration. The process, as well known,
entails space charge redistribution and emittance growth.
In most cases the beam phase distribution oscillates about
equilibrium one due to excess of energy. Appropriate
choice of the confining fields allows to control frequency
and amplitude of the oscillation so that beam distortions
remain reversible and exhibit at the exit a required phase,
for example, close to the initial phase when the distortions
are small. Designing optics with aberration compensated
by beam field may be based on the principle. An example
of the optics for matching beam into RFQ linac is
presented.
Type of presentation requested : Poster
Classification : [D03] High Intensity - Incoherent
Instabilities, Space Charge, Halos, Cooling
671 - Electron Cloud and Ion Effects
G. Arduini, CERN, Geneva
The significant progress in the understanding and control
of machine impedances has allowed obtaining beams with
increasing brilliance. Dense positively charged beams
generate electron clouds via gas ionization, photoemission
and multipacting. The electron cloud in turn interacts with
the beam and the surrounding environment originating
fast coupled and single bunch instabilities, emittance
blow-up, additional loads to vacuum and cryogenic
systems, perturbation to beam diagnostics and feedbacks
and it constitutes a serious limitation to machine
performance. In a similar way high brilliance electron
beams are mainly affected by positively charged ions
produced by residual gas ionization. Recent observations
of electron cloud build-up and its effects in present
accelerators are reviewed and compared with theory and
with the results of state-of-the-art computer simulations.
Two-stream instabilities induced by the interaction
between electron beams and ions are discussed. The
implications for future accelerators and possible cures are
addressed.
Type of presentation requested : Invited Paper
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
675 - Measurement of the Electron Cloud Properties
by means of a Multi-strip Detector in the CERN SPS
G. Arduini, P. Collier, B. Dehning, G. Ferioli, B. Henrist,
L. Jensen, J.-M. Jimenez, J.-M. Laurent, G. Rumolo, K.
Weiss, F. Zimmermann, CERN, Geneva
Electron cloud effects presently limit the performances of
the CERN SPS with LHC type beams and are of concern
for the LHC itself. Electron multipacting in the SPS
produces dramatic dynamic pressure increases and strong
transverse instabilities. In the LHC the electron cloud is
expected to significantly increase the heat load in the
cryogenics system. Estimates of these effects are based on
computer simulations of the electron cloud build-up and
of its spatial distribution in field free regions and in strong
magnetic fields. The accuracy of such simulations is
therefore a key issue for component design and for the
definition of the operating strategies for the LHC. In 2001
a multi-strip detector has been installed in the SPS to
study the electron cloud and to provide experimental data
to validate the models and to better constrain their input
parameters. After a description of the monitor
characteristics and of its associated electronics an
overview of its performance and of the results of the
measurements conducted with different proton beam
parameters are presented. The measurements are
compared with simulation results. Possible monitor
upgrades are also discussed.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1542 - Coaxial Wire Measurements in NLC
Accelerating Structures
N. Baboi, G. Bowden, J. Wang, SLAC, Stanford
The coaxial wire method provides a way of measuring
wake fields without the need for a particle beam. A
special setup has been designed to measure the loss
factors of dipole modes in some traveling and standing
wave structures for the Next Linear Collider (NLC). The
ongoing measurements will be presented. Comparisons
with teoretical predictions will be made.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1741 - Effects of Dark Currents on Beam Quality in
the JLC/NLC Linac
K. Bane, G. Stupakov, SLAC, Stanford
In high gradient structures, such as those used in the main
linac of the JLC/NLC, electrons are drawn spontaneously
and at random positions from the structure walls, and are
then accelerated in the rf fields. These so-called dark
currents are relatively weak (on the order of milliamps),
and their dipole moment, on average, should be small.
Nevertheless, according to estimates, their cumulative
effect, over the many structures in the linac, may result in
a significantly degraded final beam emittance. Using
numerical beam tracking we study the extent of this
problem in the NLC linac.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
542 - Impedance Reduction in the CERN SPS as seen
from Longitudinal Beam Measurements
T. Bohl, T. Linnecar, E. Shaposhnikova, CERN, Geneva
The longitudinal single bunch (microwave) instability of
the proton beam in the CERN SPS, observed for the first
time in 1977, became an important issue with the high
intensity and high quality beams required for transfer to
LHC. The main sources of impedance causing this
32 /52
instability were found in 1996 from measurements of the
spectrum of unstable single bunches. During the
2000/2001
shutdown the major part of an impedance reduction
programme was completed. Comparative beam
measurements from before and after this programme are
presented. While results obtained with short captured
bunches allow us to see the overall bunch stability
improvement, measurements with long bunches and RF
off allow this impedance change to be distinguished at
particular frequencies.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
679 - Large Scale Simulation Study of the Microwave
Instability in Intense Ion Beams
O. Boine-Frankenheim, I. Hofmann, GSI, Darmstadt
For a single, long bunch the tolerable longitudinal
impedance budget is determined by the fast microwave
instability [1]. In low and medium energy beams the
space charge impedance strongly affects the saturation
level of the instability. For coasting beams this was
demonstrated in Ref.[2] by means of Vlasov simulations.
In the present work large scale Vlasov simulations are
performed
in order to determine the saturation levels of the fast
microwave instability in coasting and bunched beams as a
function of the space charge impedance and of the
broadband resonator strength. The obtained 'phase space
blow-up diagrams' and 'over-shoot diagrams' are useful
for the design
of high current ring machines in general; here we apply
them to the generation of short and intense heavy ion
beams in a new facility proposed at GSI for the efficient
production and subsequent storage of exotic fragment
beams [3].
[1] E. Shaposhnikova, CERN-SL-99-008 HRF
[2] O. Boine-Frankenheim and I. Hofmann, Phys. Rev.
ST Accel. Beams 3, 104202 (2000)
[3] An International Accelerator Facility for Beams of
Ions and Antiprotons, GSI report 2001
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
457 - Coherent Beam Oscillations and Transverse
Impedance in the SPS
H. Burkhardt, G. Rumolo, F. Zimmermann, CERN,
Geneva
We describe experimental studies of single bunch
coherent oscillations in the SPS. The coherent tune shift
has been measured as a function of current and
growth/decay rates of head-tail modes have been
measured over a wide range of chromaticities, providing
information on the frequency dependence of the SPS
impedance. Simulations of coherent tune shifts and
growth/decay rates in the presence of broad-band wake
fields, space charge, chromaticity and detuning with
amplitude are then matched to the observations in order to
establish an appropriate model for the SPS transverse
impedance.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
917 - Transverse Resistive Wall Impedance for Round
Chambers of Finite Thickness
A. Burov, V. Lebedev, FNAL, Batavia
Conventionally, the resistive wall impedance is calculated
within an approximation of an infinite thickness of the
vacuum chamber. This assumption implies the skin depth
is smaller than the wall thickness, which is not always
well justified. When the skin depth exceeds the thickness,
the impedance gets to be sensitive to the vacuum chamber
exterior. In this paper, the analytic results are presented
for various surroundings and arbitrary skin-to-thickness
ratio. Effects of the finite wall thickness are important for
long next-generation rings as VLHC and for thin metallic
coatings in general size accelerators.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
923 - Transverse Resistive Wall Impedance for Elliptic
Chambers of Finite Thickness
A. Burov, V. Lebedev, FNAL, Batavia
For elliptic chamber of finite thickness, the impedances
can be expressed in terms of one of a round chamber and
geometrical form-factors. These form-factors are derived
here for a case when the outer space is vacuum. The
results are applied to the transverse coupled-bunch
instability in VLHC.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
532 - Reducing the SPS Machine Impedance
P. Collier, M. Ainoux, R. Guinand, J.-M. Jimenez, A.
Rizzo, A. Spinks, K. Weiss, CERN, Geneva
During a recent long shutdown of the SPS a major effort
was undertaken to reduce the impedance of the machine.
The task was to insert mobile RF shields into each intermagnet vacuum pumping port. The cylindrical pumping
ports had been identified as acting as accidental cavities
with a characteristic frequency in the 1-1.5 GHz range.
With some 1000 pumping ports distributed around the
machine they represented a significant fraction of the
machine impedance. The mechanical design of the
shields proved to be complex, providing good RF
performance while not degrading the pumping speed and
allowing easy installation and removal of both magnets
and shields. In addition, the SPS makes use of several
vacuum chamber sections and hence required the
development of many different models. After outlining
the specific requirements for the shields, the design
choices are detailed, together with tests made in the
laboratory for RF performance and vacuum behaviour.
33 /52
Finally, prototypes were installed in a test zone in the SPS
machine and measurements taken with beam. The
success of these tests led to the series production of
around 2500 shield sub-assemblies of 30 different types.
The installation involved the removal and re-installation
of half of the main dipole magnets, together with most of
the short straight sections. The result of all this work has
been a significant reduction in the impedance and
consequently an increase in the threshold of the
microwave instability to bunch intensities above that
required for the nominal LHC beam.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
466 - Electron Cloud Instability in the SPS.
K. Cornelis, G. Arduini, G. Rumolo, F. Zimmermann,
CERN, Geneva
The beam-induced electron multi-pacting which is created
by the LHC beam in the SPS,occurs mainly in the
dipoles. It creates a vertical electron ribbon which is
responsible for strong transverse instabilities. In the
horizontal plane we could identify a coupled bunch mode
instability. The tune shift measurements and mode
number analyses can tell us something on the electron
cloud density and the electron survival time between
bunches. In the vertical plane a single bunch head-tail like
instability occurs. A method is described by which we can
measure an equivalent impedance, created by the electron
cloud.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
136 - Closed Orbit Instability*
V.V. Danilov, S. Henderson, J.A. Holmes, ORNL, Oak
Ridge; A. Burov, FNAL, Batavia
Due to a long-range resistive wake, the closed orbit in
high-intensity circular accelerator may experience an
unstable drift. Unlike the conventional betatron
instabilities, this closed orbit instability is not sensitive to
the spread of the betatron frequencies. For bunched
beams, feedback appears to be the only way to stabilize
the closed orbit above threshold. This new instability can
be significant both for existing and for designed high
intensity rings.
*Research sponsored by UT-Batelle, LLC, under contract
no. DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
137 - An Improved Impedance Model of Metallic
Coatings*
V.V. Danilov, S. Henderson, ORNL, Oak Ridge; A. Burov,
V. Lebedev, FNAL, Batavia
A metal coating is required on the inner surface of the
ceramic injection kicker vacuum chambers of the
Spallation Neutron Source (SNS) for two reasons. First, a
coating shields the ceramic surface from the beam to
reduce the secondary emission (TiN is the candidate for
the coating because of the low secondary emission
coefficient). Secondly, a coating is required to suppress
penetration of the beam fields into the kicker at dangerous
beam frequencies (about 1 MHz). The choice for the
metal thickness is determined by the resulting impedance
and eddy-current limitations. Here we present an
improved model for the coating impedance, which
shows significant deviation from the handbook
expressions at low frequencies.
*Research sponsored by UT-Batelle, LLC, under contract
no. DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
555 - Measurements of the Coupling Impedance of the
SNS Wwindow Frame Extraction Kickers*
D. Davino, H. Hahn, Y.-Y. Lee, BNL, Upton, Long Island,
New York
The Spallation Neutron Source (SNS) Accumulator ring
extraction system includes 14 modules of window-frame
ferrite pulsing kicker magnets. Their contribution to the
beam coupling impedances is the largest among the others
ring components. Measurements of various design
options, external circuit resistances, and different ferrites
are explored in this paper. The kicker impedances are
measured with the single and the two-wire Lecher line
technique. Measurements confirm that a resistive
termination, on the external circuit, yields a significant
transverse coupling impedance reduction with respect to
the open termination.
* SNS is managed by UT-Battelle, LLC, under contract
DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
413 - Coupled-Bunch Instabilities Growth Rates in the
Next Linear Collider Damping Rings*
S. De Santis, LBNL, Berkeley
Wwe evaluate the growth rates of longitudinal and
transverse coupled-bunch instabilities in the NLC
damping rings. The two options with 1.4 and 2.8 ns
spacing between bunches are both investigated.
* This work was supported by the U.S. Department of
Energy under Contract No. DE-AC03-76SF00098.
Type of presentation requested : Poster
34 /52
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1658 - Analysis of Formulas Used in Coupling
Impedance Coaxial-wire Measurements for
Distributed Impedances*
S. De Santis, LBNL, Berkeley
In this paper we study the validity of two formulas
commonly used to derive the longitudinal coupling
impedance of a distibuted impedance from the scattering
parameters measured in the coaxial-wire setup. The
equations found, applying a differential formulation of the
classic Bethe's diffraction theory, allow for a quantitative
description of the influence of the wire thickness used in
the measurements.
*This work was supported by the U.S, Department of
Energy under Contract No.DE-AC03-76SF00098.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
493 - Higher Order Mode Absorption in TTF Modules
in the Frequency Range of the Third Dipole Band
M. Dohlus, S. Wipf, DESY, Hamburg; V. Kaljuzhny,
MEPhI, Moscow
One of the sources of transverse emittance dilution in the
superconducting e+e- linear
collider TESLA are
transverse wakefields of higher frequency modes excited
in the accelerating cavities by long trains of intense
bunches. Traditionally HOM couplers have been designed
to damp modes from the 1st and 2nd dipole bands,
however measurements showed that modes with
unexpectedly high Q-factors and R/Q values occur in the
3rd dipole band. The present work quantitatively analyses
the fields and their damping in the frequency range of the
3rd dipole band (~2580 MHz). In our investigation we use
an S-parameter concept. The accelerating module is split
into several components, such as the TTF nine-cell cavity,
different types of couplers, cold windows etc., for which
the S-parameters are independently calculated using the
MAFIA and Microwave Studio codes. We have the
ability, to calculate the scattering matrix and to study the
S-parameter dependence on frequency for a complete
accelerating module, which permits us to find the
resonant frequencies and Q-factors. An understanding of
the damping mechanisms in the 3rd dipole band was
obtained and an improved design of the HOM couplers
was proposed in order to suppress those 3rd dipole band
modes with high values of R/Q.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1212 - Evaluation and Modeling of Longitudinal
Impedance Using Current Dependent Bunch
Lengthening and Bunch Deformation Effects
K. Dunkel, U. Berges, M. Grewe, R. Heine, H. Quick, T.
Weis, DELTA, Dortmund
DELTA is a 1.5 GeV synchrotron radiation facility. The
storage ring has been designed especially for low
longitudinal impedance to allow also for high electron
densities in the case of few bunch operation besides the
standard multibunch operation mode. Bunch length and
longitudinal bunch profile depend on bunch charge as
well as on the longitudinal impedance as major factor of
influence. Measurement of turbulent bunch lengthening
and potential well distortion effects on optical basis using
a streak camera turned out to be an excellent tool to
evaluate the longitudinal impedance. The paper presents
experimental data concerning bunch lengths and
longitudinal profiles for various beam energies, intensities
and RF-settings as well as theoretical aspects (impedance
modeling of the storage ring). The analysis using the KeilSchnell-Boussard criterion confirms the theoretical value
of the impedance (broadband impedance Z/n = 0.37
Ohms). The paper also presents results concerning the
influence of two small gap insertion devices and a 3rd
harmonic cavity.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
182 - CSR Wake for a Short Magnet in
Ultrarelativistic Limit*
P. Emma, G. Stupakov, SLAC, Stanford
Using results for the CSR wake in a short magnet [1] we
obtain expressions for the wake in the limit of very large
values of the relativistic factor for both the entrance and
exit of the magnet. The analytical results are illustrated
with numerical computation of the wakes, energy loss,
and energy spread for magnets of different lengths.
* Work supported by DOE contract DE-AC0376SF00515
[1] E. L. Saldin et. al., NIM A398, 373(1997)
Type of presentation requested : Poster
Speaker :
Dr. Gennady Stupakov
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1398 - From Localization to Stochastics in VlasovMaxwell Dynamics
A. Fedorova, M. Zeitlin, IPME RAS, St. Petersburg
Fast and efficient numerical-analytical approach is
proposed for modeling complex collective behaviour and
propagation of an intense charged particle beams
described by different forms of Vlasov-Maxwell
equations. Our approach is based on a set of methods
which give the possibility to work with well-localized
bases and provide maximum sparse forms for the general
type of operators in such bases, and as consequence lead
to fast numerical algorithms in scalar/parallel calculations
[1]. We give representations for distribution functions via
the multiscale/multiresolution decomposition in nonlinear
high-localized
eigenmodes
corresponding
to
decomposition into a slow parts and fast oscillating
parts.These expansions take into account contributions
35 /52
from all underlying hidden multiscales from the coarsest
scale of resolution to the finest one to provide full
information about stochastic dynamical process. We
compare our approach with previous ones, e.g. nonlinear
delta F simulation and PIC modeling and demonstrate its
advantages. As particular limiting cases of our
construction we have standard KV and Klimontovich
distributions. Numerical modeling shows the creation of
different internal coherent structures from localized
modes, which is related to stable/unstable type of
behaviour and corresponding pattern (waveletons)
formation.
1.A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
45 - Vacuum Pressure Rise with Intense Ion Beams in
RHIC*
W. Fischer, M. Bai, M. Blaskiewicz, J.M. Brennan, P.
Cameron, H.-C. Hseuh, H. Huang, W.W. MacKay, T.
Roser, T. Satogata, L.A. Smart, D. Trbojevic, S.Y. Zhang,
BNL, Upton, Long Island, New York
When RHIC is filled with bunches of intense gold beams
a fast pressure rise is observed. The pressure rise exceeds
the acceptable limit for operation with the design
intensities. Observations of events leading to a pressure
rise are summarized. Relevant parameters include ion
species, charge per bunch, bunch spacing, and the
location in the ring. Effects that can contribute to a
pressure rise, including loss driven gas desorption and
electron clouds, are discussed, and countermeasures are
presented.
*Work supported by U.S. DOE under contract No DEAC02-98CH10886
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
787 - Longitudinal Impedance Measurements in
RHIC*
W. Fischer, M. Blaskiewicz, J.M. Brennan, P. Cameron,
BNL, Upton, Long Island, New York
The unusually clean Schottky spectra available for gold
beams in RHIC allow for a very clean measurement of
potential well distortion. By observing the variation in the
small amplitude, incoherent synchrotron tune with
intensity and bunch length the intensity dependent
longitudinal force can be measured directly. Subtle
dynamical effects associated with coherent motion are not
important allowing for measurements of very high
reliability. Measurements were cared out both at injection
energy and store, which allowed the space charge and
wall contributions to be individually determined.
*Work supported by U.S. DOE under contract No DEAC02-98CH10886
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1694 - Electron-Cloud Simulation Results for the SPS
and Recent Results for the LHC*
M. Furman, M. Pivi, LBNL, Berkeley
We present an update of computer simulation results for
the main features of the electron cloud at the Large
Hadron Collider (LHC) and recent simulation results for
the Super Proton Synchrotron (SPS). A refined secondary
electron (SE) emission model has been recently included
in the simulation code. The model has been fit to recent
experimental data published at CERN, which include
measurements at low incident electron energy. In
particular we benchmark our simulation results with
measurements, obtained by means of dedicated probes
installed in the SPS ring.
*Work supported by the US-LHC collaboration and by
the US DOE under contract DE-AC03-76SF00098.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1382 - DAFNE Broadband Impedance
A. Gallo, D. Alesini, C. Biscari, A. Drago, A. Ghigo, S.
Guiducci, F. Marcellini, C. Milardi, M. Serio, M. Zobov,
INFN-LNF, Frascati (Roma)
Beam dynamics is one of the most challenging issues of
DAFNE, due to the high single bunch current involved.
The single bunch dynamics is dominated by the short
range wakefields, that are usually expressed in terms of
machine broadband impedance. Measurements of bunch
lengthening and betatron tunes as functions of bunch
current have been performed on both rings to measure the
longitudinal and transverse broadband impedances.
Results are compared with calculations and impedance
differences between the two rings are discussed.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
10 - On the Scaling Law of Single Transverse
Instability Threshold Current vs the Chromaticity in
Electron Storage Rings
J. Gao, LAL, Orsay
Based on the single bunch transverse instability theory
established in
NIM A416 (1998) p. 186 (J. Gao), it is shown that the
instability threshold bunch current scales with the
chromaticity of the machine in a nonlinear way, with
power being 1.3 and 2.3 at low and high bunch
lengthening regime, respectively. These scaling laws are
confirmed by the experimental results from ESRF.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
36 /52
11 - On the Single Bunch Longitudinal Collective
Effects in Electron Storage Rings
J. Gao, LAL, Orsay
After giving an analytical expression for the single bunch
short range wake potential of a storage ring, we have
discussed separately the roles of linear and nonlinear
terms of the Taylor expansion of the wake potential on the
bunch longitudinal motion. The bunch lengthening and
energy spread increasing equations are established.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
41 - Impedances: Measurements and Calculations for
Non-symmetric Structures
J. Gareyte, CERN, Geneva
Coupling impedances are most often calculated for beam
enclosures of circular cross-section, and resulting
formulae are sometimes used to interpret beam
measurements, even in the case of flat chambers. This
leads to misunderstanding and inaccurate evaluations.
Rigorous analytic formulae exist for smooth, resistive
chambers of elliptical or rectangular cross-section, while
evaluations through computer programs can be found for
more complicated, non circular-symmetric geometries.
We show that these results provide a much better
interpretation of beam measurements. In addition, we
review current knowledge concerning the departure of the
resistive wall impedance from classical formulae at very
low frequencies. This behaviour becomes important for
very large machines.
Type of presentation requested : Invited Paper
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
249 - The Effect of Spread of Longitudinal Velocities
on Budker-Chirikov Instability *
Y. Golub, MRI, Moscow
The two-beams electron - ion system consists of a
nonrelativistic ion beam propagating co-axially with a
high-current relativistic electron beam in a longitudinal
homogeneous magnetic field [1]. The effect of spread of
longitudinal velocities of an electron beam on instability
Budker-Chirikov (BCI) in the system is investigated by
the method of a numerical simulation in terms of the
kinetic description of both beams. Is shown, that the
increasing of spread of longitudinal velocities of electron
beam results in the decreasing of an increment of
instability Budker-Chirikov and the increasing of length
of propagation of a electron beam.
[l] Yu.Ya. Golub, N.E.Rozanov, Nuclear Instruments and
Methods in Physics Research, A358 (1995) 479
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1158 - Evaluation of the Vertical Transverse
Impedance of the ESRF-machine by Element-wise
Wakefield Calculation
T. Günzel, ESRF, Grenoble
At the ESRF a particular strong detuning of the head-tail
modes is observed in the vertical plane. It was explained
by a corresponding transverse impedance following a
fitted Broad-Band model[1]. To examine more thoroughly
the origin of the vertical transverse impedance a
systematic evaluation of the impedance of all elements of
the machine was started. A new electromagnetic field
solver in 3 dimensions, GdfidL[2], was used for the
calculation of the wakefields. The calculations allow to
establish the impedance budget of the machine and to
improve the characterisation of the spectral form of the
transverse impedance. In particular they show that the
vertical transverse impedance weighted by the local
vertical betafunction of the tapering of the RF-liners (RFfingers) is more important than the one of the low-gap
chambers and is one of the main contributions to the
whole budget.
[1] R.Nagaoka, J.L.Revol, P.Kernel, G.Besnier,
"Transverse Instabilities in the ESRF Storage Ring:
Simulation, Experimental Results and Impedance
Modelling", PAC 1999
[2]W.Bruns, "GdfiDL: A finite difference program with
reduced memory and CPU usage", EPAC 1997
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
407 - RHIC Abort Kicker with Reduced Coupling
Impedance
H. Hahn, D. Davino, BNL, Upton, Long Island, New York
The abort kickers represent the largest contributor to the
RHIC transverse impedance budget. Increasing the
performance, beyond the design specifications, will
require impedance reduction. During beam store, the
abort kicker is not resistive terminated and its impedance
is determined by the CMD5005 ferrite. The potential of
gaining by using different, low-mu ferrites is
experimentally explored. Permeability measurements of
several ferrite types have been performed, and results
from relevant impedance measurements are reported.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
983 - A Preliminary Comparison of Beam Instabilities
among ESRF, APS, and SPring-8 X-ray Storage Ring
Light Sources
K. Harkay, ANL, Argonne; R. Nagaoka, J.-L. Revol,
ESRF, Grenoble; T. Nakamura, JASRI/SPring-8, Hyogo
A collaboration has been established among the three
highest-energy storage ring synchrotron light sources:
European Synchrotron Radiation Facility (ESRF) (6
GeV), Advanced Photon Source (APS) (7 GeV), and
Super Photon Ring (SPring-8) (8 GeV). The goal is to
enhance understanding of impedance and instability
characteristics for present performance and future
machine development. In this paper, we compare the
37 /52
instability characteristics of the three rings and present a
preliminary discussion of the similarities and differences.
Topics for future, in-depth study, such as comparing the
effect on the beam of in-vacuum undulators and small-gap
chambers, will be described.
* Work at ANL supported by the U.S. Department of
Energy, Office of Basic Energy Sciences under Contract
No. W-31-109-ENG-38.
Type of presentation requested : Poster
Speaker :
Dr. R. Nagaoka
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
197 - Measurement of Beam-Beam Tune Shift
Parameter at KEKB
T. Ieiri, J. Flanagan, H. Fukuma, E. Kikunani, M.
Tobiyama, KEK, Ibaraki-ken
In a colliding machine, the beam-beam tune shift
parameter is a good indicator of its luminosity. We can
estimate this parameter by measuring the separation
between split coherent betatron tunes. In a single-ring
collider, where the two beams have a common tune, the
observed tunes and the non-perturbed tune are simply
related. In a double-ring collider the relationship is more
complicated because of the difference in tunes of the two
rings. At KEKB, which is an asymmetric double-ring
collider at KEK, we measured the tunes with a bunch-bybunch tune meter, which had already been developed and
used in regular operation. We discuss the results of the
measurement and compare them with other
measurements.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
802 - Transition Effects in Round Pipe with Finite
Conducting Walls*
M. Ivanyan, V. Tsakanov, CANDLE, Yerevan
The study of the transit resistive wake field excitation by
relativistic electron beam in round pipe is given. Two
models have been considered: the transition of the round
pipe from perfectly to finite conducting walls and the
semi-infinite resistive pipe. In the first model, the excited
fields have been calculated by using the modal expansion
in frequency domain. The second model has been studied
based on the image charge representation technique.
*We need of financial support
Type of presentation requested : Poster
Speaker :
Doctor Michael Ivanyan
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1684 - Multi-Band Dipole Wakefields in NLC
Traveling Wave and Standing Wave Accelerators and
a Wire Measurement Technique
R. Jones, N. Baboi, SLAC, ARDA, Menlo Park; N.M.
Kroll, UCSD, La Jolla
Dipole wakefields in NLC structures have been measured
with ASSET [1] and well predicted by a circuit model [2].
However, the experimental technique is both time
consuming and expensive. Here, we report on kick factor
and synchronous frequency determination for 1st and
higher order dipole bands for both traveling wave and
standing wave accelerators via a wire measurement
technique.
This stand-alone technique is relatively
inexpensive and leads to an efficient determination of
wakefield parameters. The perturbative effect of the wire
on the dipole band is pointed out and a two wire scheme
with a limited perturbative effect is also discussed. The
partitioning of kick factors for the standing wave structure
is quite different from that previously encountered in
NLC traveling wave structures and the requirements on
higher order damping are pointed out.
[1]C. Adolphsen et al, Phys.Rev.Lett.74, 2475-2478, 1995
[2]R.M. Jones at al, EPAC 96, SLAC-PUB 7187, 1996
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
785 - Investigations of Beam Instabilities in PLS
Storage Ring
E.-S. Kim, PAL, Pohang
We present the results on studies of the beam instabilities
since
450 mA beam in 2.0 GeV has been stored in the PLS
storage ring in April 2001.
We investigate the characteristics of the transverse and
longitudinal coupled-bunch instabilities that are driven at
various different beam energies between 2.0 GeV and 2.5
GeV in the ring. The investigations on tuning of machine
parameters to cure the beam instabilities at the various
different beam energies are presented.
Type of presentation requested : Poster
Speaker :
Dr. Eun-San Kim
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
996 - Nonlinear Behaviors in Bunch-Lengthening by
Localized Impedances in Electron Storage Ring
E.-S. Kim, M.-H. Yoon, PAL, Pohang
The equilibrium particle distribution of a bunch is
investigated by using a localized delta wake and a
localized constant wake in an electron storage ring. It is
shown that multi-periodic states and resonant island states
exist stably. A mapping method is performed to show
dynamical behaviors of particle distribution by using the
Gaussian approximation. Multi-particle trackings are also
performed. Bunch-lengthenings due to composite effects
of the two wakes show different beam behaviors with
those of the individual wake. It shows new behaviors in
bunch-lengthening.
Type of presentation requested : Poster
Speaker :
Eun-San Kim
38 /52
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1662 - Coherent Microwave Synchrotron Radiation in
the VUV Ring
S.L. Kramer, B. Podobedov, BNL-NSLS, Upton, Long
Island, New York
Microwave emission, in the 3 to 75 GHz range, have been
measured from electron bunches in the VUV storage ring
for coherent and incoherent synchrotron radiation.
Coherent signals are observed at frequencies below the
predicted shielding cut-off of the vacuum chamber. The
current threshold of these signals are measured and
compared with those expected from the microwave
instability. The impedance of the ring vacuum chamber
components were estimated and compared with these
measurements. These signals also proved to be a useful
diagnostic of the level of RF noise on the beam.
Work supported by the U.S. Department of Energy.
Type of presentation requested : Poster
Speaker :
Dr. Podobedov
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
601 - Beam Coupling Impedances of Fast
Transmission-Line Kickers
S. Kurennoy, LANL, Los Alamos
Fast transmission-line kickers contain no ferrite and
consist of two long metallic parallel plates supported by
insulators inside a beam pipe. A beam is deflected by both
the electric and magnetic fields of a TEM wave created by
a pulse propagating along the strips in the direction
opposite to the beam. Computations of the beam coupling
impedances for such structures are difficult because of
their length. In the paper, the beam coupling impedances
of transmission-line kickers are calculated by combining
analytical and numerical methods: the wake potentials
computed in short models are extended analytically to
obtain the wakes for the long kickers, and then the
corresponding beam impedances are derived. As one can
expect, at very low frequencies the results are in
agreement with simple analytical expressions available
for the coupling impedances of striplines in beam position
monitors.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
158 - Beam Loading of the Super-conducting RF
System at SRRC
W.-K. Lau, L.H. Chang, C.E. Wang, M.-S. Yeh, SRRC,
Hsinchu
A superconducting cavity will be installed into the TLS
storage ring in the near future. The cavity is decided to
operate in a detuned condition for the reduction of beam
loading effects. In this study, such operation condition at
rated beam current has been examined. Multi-particle
tracking simulation has also been done to look into the
longitudinal dynamics for the bunched beam.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1529 - Frequency Analysis of the Transverse Sawtooth
Instability at the Advanced Photon Source*
E. Lessner, E. Crosbie, K. Harkay, Z. Huang, V. Sajaev,
B. Yang, ANL, Argonne
A horizontal single-bunch instability is observed at the
Advanced Photon Source above the transverse modecoupling threshold. The instability exhibits two modes:
the steady-state mode and the quasi-periodic sawtooth, or
bursting mode. The instability is self-limiting, i.e., the
oscillation amplitud saturates at up to 2 mm peak-to-peak
without beam loss, and the instability onset can occur well
below the higher, single-bunch accumulation limit. We
describe the dependence of the saturation instability
amplitude and the growth rate in terms of the amplitudedependent tune shift and the chromaticity. The tune shift
and tune spread over the instability time scale are
extracted from turn-by-turn centroid and beam-size
measurements. These are compared with the tune shift
calculated for the resistive wall and broadband resonator
impedances. Finally, we propose some machine tuning
conditions to raise the instability threshold that will allow
higher single-bunch current operation.
* Work supported by the U.S. Department of Energy,
Office of Basic Energy Sciences under Contract No. W31-109-ENG-38.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
479 - Self-bunching of Circulating Beam in Proton
Synchrotron U-70
A. Malovitsky, V. Kalynin, I. Sulygin, IHEP, Protvino,
Moscow Region
The selfbunching of the circulating beam at the magnetic
field flat-top of the proton synchrotron U-70 is studied. It
was found by computer simulation and proved by
experiments that the effect has unusually low threshold.
The Fourier analysis of the beam has shown that the
impedance of the RF cavities is the reason for the
selfbunching. It was found independently by computer
simulation and by experiments that the selfbunching
occurs in the central part of the beam and leads to the
beam displacement to smaller radius, which is a serious
problem for the slow extraction. It is shown that the
reason for such a low threshold is the filamentated
structure of the beam formed by drifting bunches. As well
as in a case of the microwave instability the threshold is
determined not by the total but by the local momentum
spread of an individual drifting bunch (filament)which
continuosly decreases during the drifting. Some measures
are proposed and proved experimentally to increase the
threshold of this undesirable selfbunching.
Type of presentation requested : Poster
39 /52
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
63 - Stability Criteria for High-Intensity Single-Bunch
Beams in Synchrotrons
E. Metral, CERN, Geneva
In circular accelerators, the interaction between the beam
and its surroundings is described in terms of bunchedbeam modes through Sacherer's formalism. As the bunch
intensity increases, the different modes, separated by the
synchrotron frequency, can no longer be treated
separately. In this regime, the wake fields couple the
modes together and a wave pattern travelling along the
bunch is created. It leads to the longitudinal and
transverse mode-coupling instabilities, aspects of which
are discussed under many different names in a variety of
different papers. The present work reviews and unifies
these approaches. It is shown that for the transverse plane,
the same intensity threshold is obtained through 5
seemingly diverse formalisms: (i) transverse mode
coupling, (ii) beam break-up, (iii) fast blow-up, (iv) post
head-tail, and (v) a quasi coasting-beam approach using
the peak values of bunch current and momentum spread
as input for the coasting-beam formula. For the
longitudinal plane, the intensity threshold is expressed in
the form of the Keil-Schnell-Boussard criterion with a
general form factor, which takes into account the
potential-well distortion and the resonator bandwidth.
Type of presentation requested : Poster
Speaker :
Dr. E. METRAL
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1404 - Destabilising Effect of Linear Coupling in the
HERA Proton Ring
E. Metral, CERN, Geneva; G.H. Hoffstaetter, F. Willeke,
DESY, Hamburg
Since the first start-up of HERA in 1992, a transverse
coherent instability has appeared from time to time at the
beginning of the acceleration ramp. In this process, the
emittance is blown up and the beam is partially or
completely lost. Although the instability was found to be
of the head-tail type, and the chromaticity and linear
coupling between the transverse planes was recognized as
essential for the instability to occur, the driving
mechanism was never clarified. An explanation of the
phenomenon is presented in this paper using the coupled
Landau damping theory. It is predicted that a too strong
coupling can be detrimental since it may shift the
coherent tune outside the incoherent spectrum and thus
prevent Landau damping. Due to these features, the name
"coupled head-tail instability" is suggested for this
instability in the HERA proton ring.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1322 - Study of Resistive-Wall Instabilities with a
Multi-bunch Tracking
R. Nagaoka, ESRF, Grenoble
Due to the presence of numerous low-gap chambers for
insertion devices, the resistive-wall instability tends to
severely influence the machine operation in light sources
such as the ESRF. Despite being a multibunch instability,
the strong short range part of the resistive-wall wake field
induces single bunch nature as well, which is reflected in
different thresholds observed according to the beam
filling. In particular, the large dependence of the threshold
on the chromaticity comes from the way the head-tail
motion of a bunch interacts with the wake field. In the
numerical analysis, however, the standard frequency
domain approach is usually limited to the special case of
uniform filling. To be able to treat the general case, a
multibunch tracking has been developed. The bunch
motion is represented with macro particles. The
nonlinearity of the betatron motion is incorporated to
evaluate its influence on the threshold. The effectiveness
of feedback is also studied. Application to the ESRF case
is presented.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1330 - Incoherent Transverse Tune Shifts due to
Resistive Low-Gap Chambers
R. Nagaoka, J.-L. Revol, ESRF, Grenoble
Large betatron tune shifts with current observed at the
ESRF, having opposite signs for the horizontal and
vertical, have been identified to be due to mean fields
generated by the resistive-wall of asymmetric cross
sections. Employing the scheme developed by K. Yokoya,
fields are computed for the actual low-gap chambers of
the ESRF machine. Tune shifts are then computed and
compared with observations. In the multibunch case, it is
found that the tune shifts are dominated by the multi-turn
effect. The apparent asymmetry of the effect between the
two transverse planes is investigated. In the single bunch
case, on the other hand, the single turn effect is expected
to be significantly enhanced, which well explains the
difficulties encountered in the single bunch operation.
Further experimental evidence is pursued utilising the
beam response to the half-integer resonance. The
influence to the coherent single bunch tune shifts and
hence to the modelling of the broadband impedance is
also discussed.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
587 - The Gaussian Approximation for a Purely
Inductive Wake Function.
S. Petracca, University of Sannio, Benevento; K. Hirata,
The Graduate University for Advanced Studies, Hayama
We study the equilibrium bunch length in electron storage
rings with a purely inductive localized wake function,
assuming the Gaussian approximation of the distribution
40 /52
function in phase space. As discussed in [1] the localized
wake can be extended to more general cases, even to
uniformly distributed wakes, described by the Haissinski
equation. To do so one should introduce the
superperiodicity N and let it grow to infinity. For N=1 we
get stable solutions with period-1 fixed points as well as
multistable states. For N>>1 the comparison of our results
with those obtained from the Haissinski equation [2]
shows good agreement and helps understanding the
validity of the Gaussian approximation.
Work sponsored in part by INFN and by EC through a
grant to S.P.
[1] K. Hirata, Part. Acc. 1987, vol. 22, p. 57-59.
[2] Y. Shobuda and K. Hirata, KEK Preprint 99-37, July
1999 A.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
590 - Impedance Boundary Conditions for
Corrugated Beam Pipe Walls
S. Petracca, T. Demma, University of Sannio, Benevento
An equivalent
wall impedance to describe
the
electromagnetic boundary conditions at corrugated pipe
walls is introduced. The general formulae for computing
longitudinal and transverse beam coupling impedances in
complex heterogeneous pipes reported in [1] together
with the impedance boundary conditions introduced
provide
a good
trade-off between computational
accuracy and ease.
Work sponsored in part by INFN
[1] S. Petracca, Phys. Rev. E 1999, vol. 60, p.6030-6041.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1319 - Probing the Transverse Impedance of the ESRF
Storage Ring
E. Pichoff, ESRF, Grenoble
We have tested at ESRF a method for probing the
transverse impedance of a storage ring. This method is
based on the measurement of the second derivative of the
beam energy loss per turn with respect to its transverse
position. Since it is safely possible, on a powerful
synchrotron radiation source like ESRF, to apply only
small vertical orbit distortion, we had to implement a
sensitive enough instrumentation set up to detect the small
beam loss variation per turn induced by the change of the
orbit. We made measurements with different kinds a of
orbit distortions: slowly oscillating transverse kicks and
fast transverse kicks able to excite beam transverse
movements at betatron oscillation frequencies. The
comparison of the results of the measurements obtained
with both kind of excitation gives indication on the shape
of the frequency dependency of the broadband part of the
impedance. This paper describes our measurement set up
and data analysis method and gives experimental results.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
613 - Numerical Investigation of Coherent
Synchrotron Radiation Driven Instability in Magnetic
Bunch Compressors
P. Piot, T. Limberg, E. Schneidmiller, DESY, Hamburg
It was recently recognized [1,2] that an initial density
modulation on an electron bunch upstream of a magnetic
bunch compressor can be enhanced during the bunch
compression process. This amplitude enhancement occurs
essentially because of the bunch self-interaction via the
coherent synchrotron radiation field. In this paper we
present numerical results that support the theoretical
expectation of the analytical model elaborated in
Reference [2]. We especially study the amplitude of the
enhancement for various initial density modulation
parameters (initial frequency, amplitude, etc...).
[1] T. Limberg, Ph. Piot, E Scheidmiller, presented at
FEL 2000 conference and to appear in NIM A
[2] E. Saldin, E. Schneidmiller, M. Yurkov presented at
FEL 2001 conference and to appear in NIM A
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1666 - Simulation Results for the Electron Cloud at
the PSR and SNS*
M. Pivi, M. Furman, LBNL, Berkeley
We present an update of computer simulation results for
the main features of the electron cloud at the Proton
Storage Ring (PSR) and recent simulation results for the
Spallation Neutron Source (SNS). In particular we
benchmark our simulation results with measurements,
obtained by means of dedicated probes installed in the
PSR ring.
*Work supported by the SNS project and by the US DOE
under contract DE-AC03-76SF00098.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1750 - Origin of the Longitudinal Density Modulation
of Unstable Bunches in the NSLS VUV Ring*
B. Podobedov, BNL-NSLS, Upton, Long Island, New
York; G.L. Carr, S.L. Kramer, J. Murphy, BNL, Upton,
Long Island, New York
Streak camera measurements showing longitudinal
density modulation of unstable bunches emitting coherent
microwave radiation were reported previously [1]. Those
measurements, however, left open the question of origin
of the wake fields creating the modulation. The two
possible candidates were the wake from the corrugated
bellow shields in the vacuum chamber or the coherent
synchrotron radiation (CSR) wake.
To distinguish
between the two we have performed another series of
streak camera measurements at different beam energies
and momentum compaction. These data favor the wake
41 /52
field from the shields over CSR as the source of the
measured modulation.
Work supported by US DOE under contract DE-AC0298CH10886
[1] B. Podobedov et al, PAC2001
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
308 - Electron-Cloud Wake Fields
G. Rumolo, F. Zimmermann, CERN, Geneva
The electron cloud gives rise to coherent and incoherent
single-bunch wake fields, both in the longitudinal and in
the transverse direction, and to coherent coupled-bunch
wakes. These wake fields can be computed using the
simulation programs ECLOUD and HEADTAIL
developed at CERN. We present the wake fields
simulated for the LHC beam in the CERN SPS and at
injection into the LHC, considering different magnetic
field configurations (field-free region, dipole, quadrupole,
and solenoid), where the magnetic fields affects both the
electron motion during a bunch passage and the overall
electron distribution in the beam pipe.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
314 - Driving the Electron-Cloud Instability by an
Electron Cooler
G. Rumolo, F. Zimmermann, CERN, Geneva; O. BoineFrankenheim, I. Hofmann, GSI, Darmstadt
We discuss the possibility to 'mis-tune' an electron cooler
in order to generate an artificial electron cloud of known
density and velocity distribution. The results of such
controlled experiment could provide further informations
on the electron-cloud instability, including its dependence
on chromaticity, beam size, beam energy, and bunch
length, and permit a calibration of the simulation code.
We present simulation results for the SIS and ESR rings st
GSI, both equipped with electron cooling devices, and
explore for which parameter combinations of beam
intensity, bunch length, solenoid field, and electron
current an instability might occur.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1218 - Observation of Ion Effects at the SPring-8
Storage Ring
M. Takao, H. Ego, Y. Kawashima, Y. Ohashi, T. Ohshima,
H. Saeki, JASRI/SPring-8, Hyogo
The SPring-8 storage ring is the high brilliant light source
facility with electron beam energy 8 GeV. If all the rf
buckets are filled with electrons, we have observed the
expansion of the vertical beam size in proportional to the
beam current. At the maximum stored current of 100 mA
the vertical beam size in uniform filling mode reaches
about twice as large as that in partially filling. To
investigate the source of the vertical expansion of the
beam size, we measured the dependence of the
bremsstrahlung on the beam filling pattern. In the case of
all the rf buckets filled the excess of the photon count
similar to the beam size expansion is observed, which
may imply the ion trapping. We discuss the vertical
expansion of the beam size induced by the trapped ion.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1557 - The LambertW Function, an Analytical
Solution of the Static Fokker-Planck Equation with a
Purely Inductive Wake Field
C. Thomas, J.I.M. Botman, TU-Eindhoven, Eindhoven; G.
Dattoli, ENEA, Frascati (Roma)
The Haissinski equation, accounting for the static
distribution of an electron beam circulating in a StorageRing and subject to a purely inductive field has an
analytical solution, which is a specific form of the
LambertW function. We show how the use of this
analytical tool allows a better understanding of the
validity of the numerical solutions and the distribution
normalization properties.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1132 - Measurements of the Impedance Introduced by
the Scrapers at ELETTRA and their Effects
L. Tosi, E. Karantzoulis, V. Smaluk, ELETTRA, Trieste
In apparent contradiction with the forseen single bunch
effect, noticeable excitations of particular narrow band
longitudinal coupled multibunch instabilities as a function
of the position of the blades of the scrapers have been
observed. In order to achieve a deeper insight of the
phenomenon and in particular that of an eventual
crosstalk between the scrapers and the RF cavities via the
beam, an exhaustive characterization of both the
longitudinal and transverse impedances of the scrapers
has been carried out.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1145 - Measurements and Simulations of the Damping
Effect of the Harmonic Sextupole on Transverse
Instabilities
L. Tosi, E. Karantzoulis, V. Smaluk, ELETTRA, Trieste
Measurements at ELETTRA have shown that the
harmonic sextupole provides Landau damping capable of
suppressing transverse coupled multibunch instabilities.
There is strong evidence that the damping is induced by
the non-linear tune spread with amplitude among the
electrons within the individual bunches together with a
change in the electron bunch distribution. Results of
measurements are compared to simulations.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
42 /52
1134 - Synchrobetatron Dynamics With a Radio
Frequency Quadrupole
A. Valishev, E. Perevedentsev, BINP, Novosibirsk
Variation of the betatron tune over the bunch length with
a radio frequency (RF) quadrupole is proposed in [1] as a
way to increase the threshold of the transverse mode
coupling instability in storage rings. Significant effect can
be achieved if the betatron tune modulation is comparable
with the synchrotron tune. However, the required timevarying field introduces a strong coupling between the
transverse and longitudinal degrees of freedom which
imposes a negative impact on the single particle
dynamics, leading to the unstable synchrobetatron
resonances. In this paper we present the results of
numerical simulation of the single particle motion in a
storage ring with an RF quadrupole, and discuss its
applicability for suppression of the transverse mode
coupling instability.
[1] V.V. Danilov, Phys. Rev. ST-AB 1, 041301 (1998).
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
865 - Examination of the Longitudinal Stability of the
HERA Proton Ring
E. Vogel, DESY, Hamburg
Since the luminosity upgrade of HERA, the proton bunch
length is relevant for the achievable luminosity. Coherent
oscillations of the proton beam during acceleration lead to
an increase of the bunch length and less luminosity. A fast
longitudinal diagnostic system was developed for an
investigation of these oscillations. One can observe
coupled-bunch oscillations, which are correlated with an
increase in the longitudinal emittance. Measurements of
the longitudinal beam transfer function and measurements
of decoherence times, together with beam echoes, are
performed. The results obtained, provide the necessary
information for the design of feedback systems.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1803 - Multi-Bunch Beam Breakup due to ResistiveWall Wake
J.-M. Wang, J. Wu, BNL-NSLS, Upton, Long Island, New
York
An integral transform, which represents the solution to the
symmetric coupled-bunch dipole beam-breakup problem
under an arbitrary wake function, is given. For the special
case of a resistive-wall wake function, a simple and
explicit asymptotic expression for the integral
representation is derived. We demonstrate by an example
of the PERL-project parameters that the growth rate of the
instability depends dramatically on the linac
characteristics, particularly on the chamber radius.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1019 - Collective Effects Study for BEPCII
J. Wang, Z. Guo, Q. Qin, J. Xing, IHEP, Beijing
BEPCII is the upgrade project of Beijing Electron
Positron Collider (BEPC). It will be a double ring
machine with beam current over 1A in each storage ring.
This paper focuses on the single beam instabilities due to
the intensive beams. With an impedance budget obtained,
the bunch lengthening and coupled bunch instability are
investigated. The photon electron cloud effect in the
positron ring and ion trapping issues in the electron ring
are studied analytically as well as with simulation. The
beam lifetime is also estimated.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1669 - Nonsingular Integral Equation for Stability of a
Bunched Beam
R. Warnock, M. Venturini, SLAC, Stanford; J.A. Ellison,
U. New Mexico, Albuquerque
The usual linearized Vlasov equation for longitudinal
motion of a bunched beam leads to a singular integral
equation, with singularity where the coherent frequency
equals a single-particle frequency. A discretization for
numerical solution of the equation in this form is not
justified. A simple transformation gives a system which
can be approximated by a matrix equation, because the
new integral operator is compact. The bunch becomes
unstable at the current for which the determinant of the
system (a nonlinear function of frequency) first has a zero
on the real axis of the frequency plane. The theory and a
realistic example will be presented.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1647 - Beam Transfer Function and Beam-Beam Tune
Shift Measurements at PEP-II
U. Wienands, SLAC, Stanford; A. Hofmann, CERN,
Geneva
Beam transfer function measurements were taken at PEPII both with single beams and with the beams colliding, in
single and multi bunch operation. For single beams, the
stability diagram shows a certain amount of damping,
presumably due to synchrotron radiation and, in case of
multi bunch operation, the bunch-by-bunch feedbacks.
The contribution of the beam-pipe impedance is presently
being evaluated. In collision, evidence for Landau
damping arising from the beam-beam tune shift has been
seen. Narrow structures on the beam response to the
stimulus as well as an apparent asymmetry of
the(broadened) peaks have also been seen consistently,
the origin of which is under investigation. As a byproduct,
the beam-beam tune shift was measured as well and
shown to be significantly larger for the low energy beam
than for the high energy beam.
Type of presentation requested : Poster
43 /52
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1722 - High Modes Contribution of the Surface
Roughness Wake*
J. Wu, J. Murphy, BNL-NSLS, Upton, Long Island, New
York
Wake field effects are important in nowadays
accelerators, which support short bunches, with high peak
current. When the bunch gets shorter, it excites more and
more high modes, and the contribution of these modes
becomes important. In this paper, we discuss the high
modes contribution of the surface roughness wake, and
we focus on the longitudinal effect.
*The work is done under the contract DE-AC0298CH10886 with the US Department of Energy
**Also at the C.N. Yang Institute for Theoretical Physics,
SUNY - Stony Brook, Stony Brook, NY 11794
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1731 - A Surface Impedance Approach for the Wakes*
J. Wu, J. Murphy, BNL-NSLS, Upton, Long Island, New
York
Based on a surface impedance approach, we treated
several wakes in a unified way. This approach also
provides a natural way to combine these wakes.
*The work is done under the contract DE-AC0298CH10886 with the US Department of Energy.
**Also at the C.N. Yang Institute for Theoretical Physics,
SUNY - Stony Brook, Stony Brook, NY 11794
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1713 - Nonlinear Localized Coherent Spectrum of
Beam-Beam Interactions
M. Zeitlin, A. Fedorova, IPME RAS, St. Petersburg
We consider modeling for strong-strong beam-beam
interactions outside preceding linearized methods such as
soft gaussian approximation or FMM (HFMM) etc. In our
approach discrete coherent modes, discovered before,
appear as the result of exact multiresolution
decomposition in the bases of high-localized wavelet or
wavelet packets functions, which correspond to
underlying coherent nonlinear eigenmodes [1]. The
constructed solutions represent the full multiscale
expansion in all internal underlying scales from slow to
fast oscillating eigenmodes. Underlying variational
method provides algebraical control of the spectrum.
1.A.Fedorova, M.Zeitlin, Seven papers in PAC01 Proc.,
arXiv preprints: physics/0106022, 0106010, 0106009,
0106008, 0106007, 0106006, 0106005.
Type of presentation requested : Poster
Classification : [D04] Instabilities - Processes,
Impedances, Countermeasures
1789 - Particle-in-cell Code Library for Numerical
Simulation of the ECR Source Plasma "*"
V. Alexandrov, A. Filippov, R. Komissarov, V. Mironov,
V. Preisendorf, V. Shevtsov, G. Shirkov, E. Shirkova, O.
Strekalovsky, N. Tokareva, A. Tuzikov, JINR, Dubna,
Moscow Region; V. Shevelko, PIAN, Moscow; T.
Nakagawa, Y. Yano, RIKEN, Tokyo; A. Anisimov, E.
Donskoi, V. Fomin, A. Golubev, S. Grushin, V. Povyshev,
A. Sadovoi, E. Vasina, V. Vatulin, R. Veselov, VNIIEF,
Sarov
A summary of resent developments of physical and
mathematical basement and the first version of the
computer code library based on the particle-in-cell
method are presented. The code library is aimed for the
3D simulation of the ECR plasma and ion production in
the ECR ion source. The particle-in-cell (finite particle)
method is one of the most powerful methods for the
numerical simulation of multicomponent ECR plasma and
electron-ion beams. This method allows studying the
detailed characteristics of plasma, taking into account the
distribution functions of particles (spatial, velocity and
energy distributions), real self and external fields, the
particle-particle interactions and many other effects. This
technique promises to provide very precise numerical
simulations and optimizations of ECR ion sources. The
first results of simulations of ECR source plasma are
presented.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
185 - Beam Dynamics Simulation via Parallel and
Distributed Computing
S. Andrianov, SPbSU, Saint-Petersburg
In this paper an approach to beam dynamics simulation
via parallel and distributed computing is discussed. This
approach is based on two modeling levels. On the first
level we find symbolic presentations both for a beam
propagator (using the matrix formalism for Lie
transformations) and for particle beam description (using
a set of model distribution functions). On this level the
LEGO-technology is used. This allows creating special
date bases of LEGO-objects. On the second level we
generate some distributed simulation flows synchronized
with each other. For this purpose the natural parallel and
distributed structures of the beam dynamics are used. The
matrix formalism presentation for the beam propagator
(Lie transformation) permits us to reduce numerical
operations to routine matrix algebra operations. This
allows us to realize the numerical simulation process on a
computer cluster or on a set of computer clusters. A
version of the prediction-correction method is used for
space-charge-dominated beam dynamics.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
44 /52
186 - LEGO-Technology Approach for Beam Line
Design
S. Andrianov, SPbSU, Saint-Petersburg
In this paper we present an approach to study some
problems of beam line modeling and optimization. We
use a modular principle for all levels of the modeling and
optimization procedures. The design code proposed by
J.Irwin with colleagues is based on modular presentation
only for beam line description. For every module (LEGOmodule) they used numerical methods for equation
motion integration and additional operations. In our
approach we introduce LEGO-objects on all levels of the
modeling and optimization processes. The beam line
components each have two main sets of LEGO-objects:
the first contains all necessary objects for beam line
component description and the second - all objects which
correspond to a transfer map (a beam propagator) as an
aggregate of two-dimensional matrices. These matrices
are computed in symbolic forms up to some
approximation order of the nonlinear aberrations. Similar
approach we developed for the space charge forces
description too. In this case a set of model distribution
function is used. Some examples of practical application
are discussed.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
758 - INTRANS 2.0 - A Windows Program for
Interactive Transport Design of Charged Particles
Transfer Lines
V. Angelov, INRNE, Sofia
INTRANS 2.0 is C++ object-oriented program with
suitable graphical user interface that allows an operator
quickly to reach desirable beamline parameters. It permits
a user to design a transfer line without requiring programs
such as MAD and TRANSPORT. INTRANS works on
PC under Windows 95 (and later), which makes the
program both user friendly and transparent. A few new
features have been added in the version 2.0 - MAD format
files for input and output, fine step tuning, simultaneous
design of several variants of line, detailed graphical and
data output, printer output and others. Dynamic
programming approach is first employed for optimization
of the line parameters. With this various qualities
INTRANS is a very suitable and effective tool for
interactive beamline design.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
741 - A General Method for the Evolution of the Phase
Space Probability Density with Applications to Beam
Physics
G. Bassi, H. Mais, DESY, Hamburg; A. Bazzani, G.
Turchetti, University of Bologna, Bologna
We present a general method for treating the time
evolution of the phase space probability density. It can be
applied to many-particles systems governed by the
Vlasov-Fokker-Planck dynamics. The method consists in
splitting the time evolution operator in the Hamiltonian
and non-Hamiltonian part. For the first one we apply the
method of the characteristics while for the second one a
finite difference scheme is used. We have found a very
good agreement with the analytically solvable systems,
long term stability and good conservation of the
symplecticity. The method can be applied to many beam
dynamics problems as for example transverse echo effect
in proton accelerators or longitudinal dynamics in the
presence of noise.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1486 - Particle Dynamic in the Ion Linear Accelerator
based on Alternating Phase Focusing with Moving
Center of the Bunch
V. Bomko, A. Kobets, Y. Meleshkova, B. Zajtsev, KIPT,
Kharkov
The version of alternating phase focusing in an ion linear
accelerator is discussed. It is based on a periodic shift of
the bunch from the region of negative phases to that of
positive ones and conversely, with a constant excess of
the bunch center energy over the synchronous particle
energy both in positive and negative phases. The
compromise between the inconsistent requirements of
radial and phase stability is achieved by selection of phase
shift depth, the number of accelerating cells along
focusing and bunching regions, and by excess of the
bunch center energy over the synchronous particle energy.
A high efficiency of the version is demonstrated by the
example of calculations of the accelerating structure and
beam dynamics of a heavy ion linear accelerator with a
high ratio of atomic mass to charge, A/q=32.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1182 - RFQ Simulation Based on New Possibilities of
LIDOS.RFQ Codes
B. Bondarev, A. Durkin, Y. Ivanov, I. Shumakov, S.
Vinogradov, MRI, Moscow
Recent enhancement of LIDOS.RFQ code package took
an opportunity to investigate some new problems of RFQ
operation - the possibility of simultaneous acceleration of
different sorts of ions, including negative ions; the role of
construction mismatching of various types; the influence
of residual gas on beam dynamics, etc. Some results of
these new investigations are presented in this work.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1437 - GdfidL on Clusters of Workstations
W. Bruns, TU-Berlin, Berlin
The electromagnetic field solver GdfidL has been
extended to run efficiently on loosely coupled parallel
systems, such as clusters of workstations. A
45 /52
computational volume which is discretised using a regular
grid can be easily partitioned such that each processor has
the same number of gridcells. If for every gridcell the
needed computation is the same, the partitioning is easy.
For typical accelerator components, most gridcells are
filled with metal, therefore no fields need to be computed
in these cells. When such a geometry is parellelised
naively, the computational efficiency goes down to about
10%, since most processors work on electrical conducting
cells. In that case, the problem is finding a partitioning
such, that each processor gets the same number of
gridcells filled with vacuum. The paper describes the
implemented
algorithms
for
partitioning
the
computational volume and for computing the
electromagnetic fields. The total achieved computational
efficiency is about 60%.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
213 - Beam Dynamics Simulations for the PITZ RFGun
R. Cee, M. Krassilnikov, S. Setzer, T. Weiland, TUDarmstadt, Darmstadt
The Photo Injector Test Facility at DESY Zeuthen (PITZ)
is dedicated to the optimisation of laser driven rf-guns as
applied for Free Electron Lasers (FEL) and linear
colliders. The rf-gun currently under test is a 1.5 cell
cavity operated in the pi-mode at 1.3 GHz. It is designed
for subsequent use at the TESLA Test Facility (TTF).
Beam dynamics simulations deliver an essential
contribution to the understanding of the emittance growth
within the gun and can thus assist in reaching the aim of
high quality beams. Possible reasons for emittance growth
we investigated in our simulations are an initial transverse
beam offset with respect to the field symmetry axis and an
inhomogeneous rf- field with different maximum field
gradients in the half and the full cell. The simulations
were carried out with the TS2 and TS3 modules of the
MAFIA programme which are particle in cell (PIC) codes
for two and three dimensions.
Work supported in part by DESY, Germany and DFG
(FOR 272/2-1)
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
907 - Magnetic Helical DNA Type Undulator*
M. Dan, Univ. "Babes-Bolyai", Cluj-Napoca, Cluj; A.O.R
Cavaleru, V. Niculescu, INFLPR, Bucharest; V. Babin,
INOE2000, Bucharest
A new theoretical model of an undulator for free electron
lasers in a helical DNA type magnetic field is presented.
The undulator is a wire which mimics DNA structure. In
this new structure the current is circulating in two distinct
widding creating alternating dipoles. Semi-analytical
expressions of the magnetic field components were also
obtained. This new treatment of the problem could be
extended to the nonlinear dynamical analysis of the
electrons in the studied structure.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
942 - The Particle Beam Optics Laboratory:
Enhancing Scientific Productivity for the Accelerator
Community
G. Gillespie, GHGA, Del Mar
The increasing use of accelerators for a variety of
practical applications, as well as for many types of
research studies, has resulted in an expanding need for
software that focuses on the requirements of the
accelerator community. This paper summarizes several
recent advances in software developed to meet a number
of those requirements.
The Particle Beam Optics
Laboratory (PBO Lab) family of software applications
was designed to support three primary areas: beamline
design, accelerator operations, and personnel training. All
of the PBO Lab applications are based upon an innovative
software framework designed specifically for the
accelerator community: the Multi-Platform Shell for
Particle Accelerator Related Codes (SPARC-MP). The
SPARC-MP framework includes a sophisticated beamline
object model, an extensive library of graphic user
interface (GUI) components, and supports a variety of
particle optics codes and add-on tools. The PBO Lab
Basic Package provides a unique and intuitive GUI whose
signature feature is a drag and drop graphical beamline
construct kit. The SPARC-MP beamline object model
provides the foundation for the icon-based manipulation
of accelerator components and models. An interactive
tutorial system links physics and engineering concepts
and discussions to individual icons, providing a unique
computer based teaching tool that has been used for
several years by the U. S. Particle Accelerator School.
Particle optics codes have always been important tools for
accelerator science, and a number of popular optics codes
have been integrated into the framework and several are
now available commercially as PBO Lab Application
Modules,
including
MARYLIE,
TRANSPORT,
TURTLE, DECAY-TURTLE and TRACE 3-D. Complex
optimization problems can be addressed by using a new
Optimization Module which seamlessly integrates the
NPSOL and MINOS nonlinear, constrained, optimization
programs into PBO Lab.
An overview of the current
version of PBO Lab is described and several of the
capabilities are illustrated.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
309 - Simulating Dynamic Effects in Superconducting
Magnets at the LHC
M. Hayes, CERN, Geneva
Changes in multipole errors (during injection or ramping)
of the superconducting magnets in the LHC affect
important beam parameters such as the closed orbit, tune
46 /52
and chromaticity. In the following it is described how the
currently available simulation tools (MAD and
SIXTRACK) have been altered to simulate this time
dependence and in order to reproduce these effects.
Preliminary results are shown.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
560 - Study of Coherent Modes caused by Parasitic
Beam-beam Interactions using a Fast Multipole
Algorithm (FMM)
W. Herr, CERN, Geneva; F. Jones, TRIUMF, Vancouver
Head-on as well as long range beam-beam interactions
can excite coherent beam-beam modes. The quantitatively
correct simulation is often hindered by the required
precise calculation of the forces on the individual
particles. We have recently developped a simulation
program that allows the exact calculation of both head-on
and long range forces in a reasonable computing time. It
is based on a Hybrid Fast Multipole Method (HFMM).
We shall show that the coherent modes from head-on and
long range interactions are of significantly different
nature and their behaviour can be understood in the
framework of a perturbative treatment and demonstrated
with our multiparticle simulation program.
Type of presentation requested : Poster
Speaker :
werner Herr
Classification : [D05] Code Developments and
Simulation Techniques
equation in 3-D. For an accelerator with long bunches, the
3-D problem is usually reduced to 2-D, because the
transverse motion can be decoupled from the longitudinal
due to very different characteristic times. The simulation
of large macroparticle ensembles requires rapid
evaluations of space-charge forces. Fast field solvers are
usually based on Fourier-transform methods, but they are
not applicable for arbitrary geometries of walls. For
arbitrary walls, the solution for Poisson's equation can be
derived using a Green function, which is numerically
calculated on discrete mesh points. For simple wall
geometries, e.g., circle and ellipse, it can be expressed
analytically. Usually, such technique results in slow
solvers. We discuss here a method, which combines a
Green function technique and Fast-Fourier transformation
solver. In the first step, the Green function technique is
used for arbitrary walls to calculate potentials on an
intermediate rectangular boundary, which includes all
macroparticles. In the second step, Fast-Fourier
transformation solver calculates potentials inside this
rectangular boundary with given potentials. Preliminary
numerical results will be reported.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
691 - ULTRASAM - 2D Code for Simulation of
Electron Guns with Ultra High Precision
A.V. Ivanov, M.A. Tiunov, BINP, Novosibirsk
The program package UltraSAM intended for the
simulation of cylindrically symmetric electron guns and
collectors is presented. The package is the further
development of the program package SAM and combines
the boundary elements method, used in SAM, with curved
meshes for space charge description. Advanced models of
electron emission and beam dynamics are developed. The
thermal spread simulation of the initial velocities of
particles at a cathode is also added. Due to this the
precision of high perveance guns evaluation is improved,
and the scope of devices that can be simulated is
essentially extended. The results of the simulations and
measurements for several electron guns are presented.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
210 - Impact of the RF-Gun Power Coupler on Beam
Dynamics
M. Krassilnikov, R. Cee, T. Weiland, TU-Darmstadt,
Darmstadt
A production of high brightness electron beams is
necessary for FEL operation. Since the beam quality
degrades as the beam propagates along the beam line,
every perturbation factor has to be studied. The electron
beam dynamics in the TESLA Test Facility (TTF DESY)
rf-gun has been investigated with the on-line simulation
tool V-Code. While some of the rf-gun misalignments can
be corrected by an earlier developed alignment procedure,
the aside power coupler causes a field asymmetry
resulting in unavoidable steering forces. The dependence
of the accelerating mode offset on the longitudinal
coordinate, calculated with CST Microwave Studio, has
been implemented in the V-Code. Assuming a possible
laser beam offset on the cathode additionally to the given
rf field asymmetry one can explain the dependence of the
electron beam offset measured by the first beam position
monitor (BPM1) on rf phase. The measured data as well
as simulation results are presented.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
622 - A Method for Numerical Solution 2-D Poisson's
Equation with Image Fields
V. Kapin, NIRS, Chiba City
Simulation of high intensity accelerators leads to the
calculation of space charge forces between macroparticles
in the presence of acceleration chamber walls. To
calculate space-charge forces, one solves the Poisson's
1217 - Single-Bunch Instability of Positron Beams in a
Rare Electron Plasma
K. Lotov, BINP, Novosibirsk; G. Stupakov, SLAC,
Stanford
Single-bunch instability of a short and dense positron
beam in a photo-electron plasma is studied numerically
with code LCODE. The code was originally developed
47 /52
for studies of plasma wakefield acceleration. It is twodimensional and fully relativistic, with both the beam and
electrons modelled by macro-particles. The instability is
shown to affect the rear part of the beam, right after the
arrival of nearby electrons to the axis. As the result, the
emittans of the whole beam grows exponentially. The
instability can be stabilized by an external longitudinal
magnetic field. The field does not itself stabilize the
instability, but prevents the electrons from going to axis
once they were thrown to the wall by the previous bunch.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1459 - Application of UAL-Based Correction Schemes
to the SNS Accumulator Ring*
N. Malitsky, A.V. Fedotov, I. Papaphilippou, J. Wei, BNL,
Upton, Long Island, New York
The SNS ring correction schemes were tested using the
Unified Accelerator Libraries (UAL). The capabilities of
some already existing algorithms, such as tune and
chromaticity fitting , orbit and coupling correction [1],
were applied to beam dynamics studies. In addition, the
option of beam-based correction schemes was
investigated and compared with the purely analytic
approach.
* SNS is managed by UT-Battelle, LLC, under contract
DE-AC05-00OR22725 for the U.S. Department of
Energy. SNS is a partnership of six national laboratories:
Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los
Alamos, and Oak Ridge.
[1] R.Talman. A Universal Algorithm for Accelerator
Correction. AIP 255, 1992.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
746 - Simulations of Transient Phenomena in
Thermionic RF Guns
V. Mytrochenko, V. Kushnir, A. Opanasenko, KIPT,
Kharkov
The report is dedicated to simulation of transient
phenomena in resonant systems of thermionic RF guns
caused by beam loading effect. The technique of the
PARMELA code using for evaluation of a resonant
system excitation by electron bunches is described. The
results of transient phenomena simulation in some RF
guns are given as examples.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
844 - Bunching of Weakly Relativistic Intense Electron
Beam
V. Mytrochenko, M. Ayzatsky, V. Kushnir, A.
Opanasenko, KIPT, Kharkov
Problems connected with strong influence of space
charge forces on bunch formation arise under
development of microwave sources and linac injectors
with comparatively low energy of electron beam (when
energy of particles is several tens of keV). Results of
intense electron beam dynamics simulation in bunching
systems are presented in this report. The main attention
was given to the bunching process in resonant systems
based on a coupled cavity chain.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1458 - Simulations of Flip-Flop Behavior of Colliding
Beams
I. Nesterenko, P. Ivanov, D. Shatilov, E. Simonov, BINP,
Novosibirsk
In this paper computer simulations of flip-flop behavior of
transverse sizes in framework of strong-strong model for
e+e- colliding beams are presented. Features of this type
instability for both flat and round beam concepts are
discussed.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
460 - Twisted Radial Sinusoidal Modulated Wiggler
V. Niculescu, INFLPR, Bucharest, sect. VI; V. Babin,
INOE2000, Bucharest-com. Magurele; M.R. Leonovici,
Univ.Buc., Bucharest-com. Magurele
For free electron laser wigglers a new theoretical model
was presented. The wiggler is a stack of radial sinusoidal
modulated rings of wires which in xy plane are described
by
the
following
type
of
equations
:
x=(R+pRsin(k*teta))*cos(teta),y=(R+pRsin(k*teta))*sin(t
eta),z=cst.; k=2,3,4,...;p=m/n,m<n;m,n integers. Each
wire is twisted relative to precedent one with a constant
angle.The x and y magnetic field components of B for a
large range of ratio of R to h (where R is wiggler radius ,h
step between wires) are negligible. A saw - tooth
periodicity of the z magnetic field components was
observed.This new structure has a high transversatility of
the magnetic field.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1582 - Beam Dynamics Optimization in RFQ
Structures
A. Ovsyannikov, I. Antropov, D. Ovsyannikov, SPbSU,
St.Petersburg; B. Bondarev, A. Durkin, MRI, Moscow
In this paper mathematical methods of optimization of
beam dynamics in RFQ structures are developed.
Different mathematical optimization models of charged
particles dynamics are suggested. BDO-RFQ code that is
created on the base of these methods and models allows
modeling and optimization of beam dynamics at various
stages of investigation. In particular, longitudinal and
transverse motions can be considered separately. For the
estimations of beam dynamics the system of functionals
is introduced. It allows conducting multi-goals
48 /52
optimization with taking into account various limitations
for RFQ structure.
Type of presentation requested : Poster
Speaker :
Dr. A. Ovsyannikov
Classification : [D05] Code Developments and
Simulation Techniques
355 - Beam Loading the Standing Wave Injector on
the Base of Evanescent Wave
S. Perezhogin, M. Ayzatsky, K. Kramarenko, KIPT,
Kharkov
Standing wave injectors on the base of evanescent waves
are considered. Injectors consist of the fragments of the
cylindrical discloaded waveguide and biperiodic
cylindrical discloaded waveguide. The parameters of the
systems are selected in such a way, that at the working
frequency the resonant oscillation in the injector
corresponds to the evanescent wave of the boundless
periodic structure. It gives possibility to create in the
injector the increasing amplitude distribution, which
improves the bunching process at the initial stage of
acceleration. The simulation of the beam dynamics is
carried out with taking into account the beam loading.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
632 - Symplectic Integrator for Particle Tracking in
Complex Magnetic Field
P. Piminov, E. Levichev, BINP, Novosibirsk
High field wigglers for synchrotron radiation production
have usually rather complex distribution of magnetic
field, and particle motion through it can hardly be treated
analytically. This paper concerns a simple and reliable
receipt for a symplectic algorithm to track a particle
through such fields. Input data for numeric integration are
taken directly from results of magnetic mapping or
simulation of 2D field values array. A 3-pole 7 T
superconducting wiggler is considered as an example.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1173 - A Fast 3D Multigrid Based Space-Charge
Routine in the GPT Code*
G. Pöplau, U. van Rienen, Universität Rostock, Rostock;
M. de Loos, B. van der Geer, Pulsar Physics, Soest
Fast calculation of 3D non-linear space-charge fields is
essential for the simulation of high-brightness charged
particle beams. We report on our development of a new
3D space-charge model that scale nearly with the number
of particles in terms of CPU time. The model is based on
a multigrid Poisson solver used to solve the electrostatic
fields in the rest frame of the bunch. The multigrid
Poisson solver is adapted to the non-equidistant
rectangular grids generated in order to get a good
approximation of the particle distribution while keeping
the number of grid points as small as possible. Lorentz
transformations are applied for the transformation from
lab- to rest-frame and vice-versa. The new algorithm is
implemented as a custom element in the General Particle
Tracer (GPT) code. Numerical results will be presented.
*supported by a research grant from DESY, Hamburg
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
85 - A New Technique to Compute Long-Range
Wakefields in Accelerating Structures
J.-Y. Raguin, J. Prochnow, W. Wuensch, CERN, Geneva
A new technique is proposed to compute the long-range
wakefields based on a scattering matrix formalism which
relies heavily on post-processed data from the commercial
finite-element code HFSS. To illustrate the accuracy and
the speed of this technique, computations of the longrange wakefields of conventional constant-impedance
structures and of structures damped with waveguides are
given. The efficiency and accuracy of the technique is
achieved because the characteristics of periodic structures
can be computed using single-cell data. Damping and
synchronism effects are determined from such a
computation. The results are compared with a direct-time
domain approach.
Type of presentation requested : Poster
Speaker :
Dr. J.-Y. Raguin
Classification : [D05] Code Developments and
Simulation Techniques
724 - MAD-X, an Upgrade from MAD8
F. Schmidt, H. Grote, CERN, Geneva
The development of MAD8 has been suspended for many
years. At the start of 2001
it was decided to revive it and put it into a more
maintainable form since it is needed for the LHC during
design and operation. In particular, the home grown
dynamic data management in Fortran77 limits further
extensions, and is not guaranteed to survive for another
ten years. In fact, MAD-X has been originally planned to
be a copy of MAD8 with a more modern data
management. The data structures that hold the
information about the accelerator, and the interfaces to the
modules are written in C which provides the dynamic data
structures needed. Contrary to MAD8, the MAD-X
modules are designed as truly independent entities; they
will be much simpler and therefore better maintainable. It
was also thought important to spread the responsibility for
the various MAD-X modules among several accelerator
physicists. Lastly, an upgrade of MAD-X is being planned
to improve the physics models and to include map related
tools using Etienne Forest's PTC code.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
391 - FEL Photoinjector Simulation Studies by
Combining MAFIA TS2 and ASTRA
49 /52
S. Setzer, R. Cee, M. Krassilnikov, T. Weiland, TUDarmstadt, Darmstadt
For the successful FEL operation a high brightness low
emittance beam is of crucial importance. For a detailed
investigation of the emittance development the
simulations should not be restricted to the RF-Gun only.
That is why the two simulation codes MAFIA TS2 and
ASTRA have been combined in order to make use of their
individual advantages. The PIC code MAFIA TS2 is used
for detailed modelling of the space charge effects inside
the RF-Gun. By using a data interface the beam dynamics
downstreams the RF-Gun is simulated by ASTRA which
is capable of simulating long accelerator structures
efficiently. In this paper we discuss the advantages and
limitiations of both simulation approaches. Additionally
the results of combined simulations using both codes are
presented.
Work supported in part by DESY Hamburg.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1224 - New 2D Real-time Radiation Field Simulator
T. Shintake, KEK, Ibaraki-ken
Real time computer simulator for 2D radiation field
pattern has been developed. Graphic shows radiation from
a moving charge in free space. Instead of processing timeconsuming integration of the retarded potential, it simply
tracks the flow of "information points" emitted from
moving charge. The light aberration is correctly
implemented to ensure relativistic conversion. Pre-coded
models are synchrotron radiation, dipole, undulator
radiations, as well as radiations from your mouse
movement.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1044 - Beam Tracking Study for the Large Aperture
Bump System
M. Shirakata, H. Fujimori, Y. Irie, KEK, Ibaraki-ken
Generally, the magnet aperture tends to be large with
respect to the core length for the high intensity
accelerators. The effect of the fringe fields on beam may
cause the unexpected interferences when the magnet
aperture is very large. In joint project of JAERI and KEK,
the compact beam bump system is required for the beam
injection of the 3 GeV booster ring. The eight magnets
bump system is under consideration, here. The core length
of bump magnets cannot be so long and the strong fringe
fields are expected. Because the distance between the
adjacent bump magnets is also close, the fringe fields
enhance or override each other and the magnet effective
lengths change dinamically. The beam tracking study is
discussed of the large aperture bump system with the
crossing fringe fields from the closely aligned bump
magnets.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1495 - An Analysis Tool for RF Control for
Superconducting Cavities
S.N. Simrock, DESY, Hamburg; V. Ayvazyan, A.
Vardanyan, Yerevan Physics Institute, Yerevan
The rf control analysis tool consists of a set of library
blocks to be used with SIMULINK. The tool allows to
study the performance of a given rf control design. The
library blocks include models for the superconducting
cavities, the rf power source, the beam, and the rf
feedback system.
The rf control relevant electrical and mechanical
characteristics of the cavity are described in form of timevarying state space models. Included are perturbations
from Lorentz force detuning and microphonics with the
appropriate parameters for several mechanical resonances.
The power source is calibrated in terms of actual power
and includes saturation characteristics and noise. An
arbitrary time structure can be imposed on the beam
current to reflect a macro-pulse structure and bunch
charge fluctuations. For rf feedback several schemes can
be selected: Generator driven system or self-excited loop,
traditional amplitude and phase control or I/Q control.
The choices for the feedback controller include analog or
digital approaches and various choices of filters for the
gain stages. Feed forward can be added to further
suppress repetitive errors. The results of a performance
analysis of the TTF Linac rf system using these tools are
presented.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
141 - Resonance Strengthening and Damping of
Synchrotron Oscillations
A. Taratine, JINR, Dubna, Moscow Region
Resonance strengthening and damping of synchrotron
oscillations of collider bunch halo particles was studied
by simulation. Additional longitudinal kicks are applied in
resonance with the synchrotron oscillations of the
particles. It was shown that the strengthening of particle
synchrotron oscillations can be high efficient. The
resonance damping of particle synchrotron oscillations is
only possible when the inverse population of the
accelerated bunch halo is realized. Resonance method of
synchrotron oscillation strengthening can be used for the
extraction of beam halo particles with a bent crystal to
improve the background conditions for colliding beam
experiments and to fulfill simultaneously some fixed
target experiments. Possibility to use this method for high
intensity beams is also discussed.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
50 /52
215 - BRICTEST: a Code for Charge Breeding
Simulations
V. Variale, INFN-Bari, Bari; T. Clauser, A. Raino',
Universita' di Bari e INFN-Bari, Bari; M. Claudione,
Universita' di Bari, Bari
In the framework of the SPES project [1], already funded
by INFN at the LNL (Padua) in Italy, for Radioactive Ion
Beam (RIB) production, an experiment of a charge
breeder device, BRIC, is in progress at Bari INFN section
[2]. BRIC is an EBIS type ion charge state breeder in
which a quadrupolar rf field is added at the trapped ion
region to introduce a selective containment with the aim
to increase the wanted ion containment efficiency. A code
that study the ion charge state evolution in the trap region,
which allows of choosing the rf quadrupole parameters to
optimise the ion charge breeding efficiency, has been
recently developed in Bari. In this paper the main feature
of the code, named BRICTEST, and the simulation test
will be presented and discussed.
[1]"SPES Project Study", LNL-INFN (REP), 145/99
[2]G. Brautti,T. Clauser,A. Raino',V. Stagno, V.
Variale,"BRIC: An EBIS Design for Charge State
Breeding in RIB.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
955 - High Current Beam Simulation using
Templates*
L. Vorobiev, R.C. York, NSCL, East Lansing
Charged particle beam dynamics including space charge
and image forces was simulated in both two and three
dimensions with a newly developed code. The formalism
for this new code is based on the template potential
techique and can be employed for calculational
approaches ranging from envelope equations to particlein-cell (PIC) models in either two- or three-dimensional
geometries. The self-consistency of the method is not
complete for all cases but is appropriate for a large class
of beam distributions and conducting boundary
configurations. The calculational speed is high and
memory demands are moderate in comparison with
conventional PIC algorithms.
*Work supported by the U.S. Department of Energy
Contract No. DE-FG02-99ER41118
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1473 - Aberration Coefficients of High Order Optics
for Beam Transport Channels
I. Yudin, JINR, Dubna, Moscow Region
In this paper the nonlinear high order beam optics is built
for a wide list of different elements of the charge particle
transport channels. The optical elements are a drift space,
a bending magnet, a quadrupole, a sextupole, an octupole,
a solenoid, a toroidal ("orange" type) magnetic lens, an
accelerating tube. The motion equations are written. The
solution techniques is the Green' function method (GFM).
Polarization effects and self-coordinate space charge
analysis are performed to integrate it into the proposed
model. The programme realization of our model is
presented. Some results of the investigation are
demonstrated.
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
694 - A Conformal Scheme for Wake Field
Calculation*
I. Zagorodnov, T. Weiland, TU-Darmstadt, Darmstadt
The existing computer codes experience problems in
wake field calculations for long smooth structures. To
overcome them a new staircase free scheme for
rotationally symmetric case is developed. It allows to
calculate wake potentials for ultra short bunches in long
arbitrary shaped perfectly conducting geometries. Unlike
previous conformal approaches the scheme has a second
order convergence without the need to reduce the
maximal stable time step of conventional staircase
method. Several numerical examples are presented and
the algorithm is compared to other approaches.
* Work supported in part by the Deutsche
Forschungsgemeinschaft, Graduiertenkolleg Physik und
Technik von Beschleunigern
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
1519 - Computation of RF-Properties of Long and
Complex Structures*
U. van Rienen, H. Glock, D. Hecht, K. Rothemund,
Universität Rostock, Rostock
Numerical calculation of RF-properties of accelerating
structures are normally done by numerical field solving
codes such as MAFIA or Microwave Studio(TM). But if a
certain amount of details has to be considered in long
structures, e.g. the TESLA accelerating channel, the
numerical effort grows to a level where the computational
resources reach the limit of todays computer hardware.
Therefore we have been developing a method called
Coupled S-Parameter Calculation (CSC) which is based
on a scattering parameter description. It allows the
splitting of large structures into several components and
results in the entire structure´s scattering properties, or, if
all external ports are closed, in the eigenfrequencies and modes of the structure. The S-parameters of the
components are computed by customary field solving
codes. Exploiting all possible symmetries and repetitions
can reduce the computational expense, especially if
certain components are of rotational symmetry which
allows for 2D-calculation. Additional a frequency range
can be specified concentrating on the frequency band of
interest, hence neglecting lower frequencies, which is not
possible for the majority of eigenmode solvers. The
authors want to demonstrate the capabilities of CSC
reporting results on the effect of different HOM-coupler
51 /52
geometries in the TESLA channel and compare the effects
of different cavitiy- and coupler arrangements.
* work supported by DESY, Hamburg
Type of presentation requested : Poster
Classification : [D05] Code Developments and
Simulation Techniques
52 /52