SLAC NATIONAL ACCELERATOR LABORATORY
ACCELERATOR RESEARCH DIVISION
April, 2011
FY2011-Q2 Quarterly Report (Jan-Mar, 2011)
* department mission statements and function in blue, publications in dark red
Table of Contents:
1. ARD Administration
2
2. Advanced Accelerator Research Department
AARD – Microwave
AARD – Plasma
AARD – Laser
AARD – Feedback & Dynamics
3
3
4
4
6
3. Beam Physics Department
Collective Effects
FEL Physics
Advanced Computation
Beam Optics & Non-Linear Dynamics
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6
8
10
11
4. Accelerator Design Department
ILC Systems R&D
ILC RF Systems
FNAL Project-X
X-Band
LARP
SuperB
End Station A
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13
15
16
16
17
18
18
5. Accelerator Physics & Engineering Department
ATF2
CTF3
FACET
LCLS
LCLS-II
LHC
NLCTA
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21
21
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22
23
23
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6. Test Facilities Department
ASTA
NLCTA
FACET User Area
End Station A
End Station B
ECHO Experiments
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24
24
25
25
25
25
A U.S. Department of Energy Research Facility Operated Under Contract by Stanford University
Accelerator Research Division Quarterly Report – 2001/Q1
1. ARD Administration
The Accelerator Research Division (ARD) is a division within SLAC’s Accelerator Directorate. The
division is supported with an annual budget of roughly 40 M$ from the US Department of Energy,
Offices of Basic Energy Science and High Energy Physics. It consists of roughly 110 physicists,
engineers and technicians, including 5 Stanford faculty members, and is divided into five departments:
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Advanced Accelerator Research
Beam Physics
Accelerator Design
Accelerator Physics and Engineering
Test Facilities
ARD’s mission is to develop accelerator science and technology that will enable new accelerators in
photon science and high energy physics as well as other fields of science, medicine and industry with
R&D aimed at near-term, mid-term, and long-term development. It has a world renowned research
program in advanced acceleration techniques and is engaged in R&D on some of the most advanced
accelerators in the world including the Large Hadron Collider at CERN and the Linac Coherent Light
Source at SLAC. The division operates three test facilities dedicated to accelerator research: the
Accelerator Structure Test Area, the NLC Test Accelerator and the FACET facility.
This report is intended to highlight ARD’s research program and describe progress and advances made in
the previous fiscal quarter. Its intended audience is the Directorate and Laboratory management. In
addition it is will help ARD staff understand the breadth and strength of the division research program
and work that their colleagues are engaged in.
General and more specific information about ARD can be found in:
slacportal.slac.stanford.edu/sites/ard_public/Pages/Default.aspx
and the ARD organization chart is shown in:
slacportal.slac.stanford.edu/sites/ard_public/SiteCollectionDocuments/ARDOrgChart-feb-2011-v2.pdf.
The Invited Accelerator Seminars during the quarter were:
 Mike Borland, APS, “A Comparison of Ultimate Storage Rings as Next Generation X-ray
Sources”
 Claudio Pellegrini, UCLA, “Fifth Generation FEL Light Sources”
 David Robin, LBL, “Novel Design of Gantry Optics for Carbon Cancer Therapy Accelerator”
 Pietro Musumeci, UCLA, “The Development of Relativistic Ultrafast Electron Diffraction: Using
Particle Accelerators to Watch Atoms Move in Real Time”
 Steve Geer, FNAL, “Muon Collider R&D”
These talks are posted on slacportal.slac.stanford.edu/sites/ard_public/ardhq/seminars/Pages/default.aspx.
FACET Construction At the end of the Q1, the FACET project was 80% complete and held 1.3M$ of
management reserve on an estimated cost to complete of 2.6M$. Mechanical installation in Sector 20
began in late Q1 and continued through Q2. At the end of March the project was 93% complete and held
400K$ of reserve on an estimated cost to complete of 1M$. It is expected that FACET construction will
be complete in early May, 2011 with first beam in mid-June.
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Accelerator Research Division Quarterly Report – 2001/Q1
2. Advanced Accelerator Research Department
The Advanced Accelerator Research Department (AARD) is dedicated to basic and applied research in
accelerator science with the goals of advancing the state-of-the-art and educating accelerator scientists.
Our investigations lie at the forefront of accelerator physics, and incorporate a wide variety of fields
ranging from microwave engineering, plasma physics, electromagnetic theory, and ultra-fast lasers to
physical optics, materials science, formal control theory, ultrafast electronics, and nanofabrication
engineering and design. AARD efforts focus on understanding and extending the limits of accelerator
technology to expand capabilities in energy, luminosity, beam power, and timescale to extend the reach of
discovery science. Primarily developed for High Energy Physics and Basic Energy Science, these
accelerator technologies will also benefit medicine, food safety, biology, and homeland security.
The department consists of four groups focusing on the four main research directions:
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Microwave : Development of normal conducting accelerators and power sources, with a focus on
understanding the limitations in high-gradient and high-frequency microwave structures.
Plasma: Use of short, intense pulses of electrons and positrons to create waves in a plasma
(ionized gas) capable of producing orders of magnitude higher accelerating gradients than
traditional accelerators
Laser: Investigation of techniques for accelerating electrons and positrons using lasers and
dielectric microstructures, with acceleration gradients orders of magnitude larger than traditional
accelerators
Feedback & Dynamics: Development of novel ultrafast and wide-bandwidth electronic circuits,
signal processing systems, and laboratory measurement techniques for particle accelerators
AARD – Microwave Group:
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Structure Manufacturing Technology (Collaborative work with CERN & KEK)
o Coordinated the work for two TD24_VG1.8 structures. Finished construction: Structure with
SLAC flanges will be vacuum backed and tested at NLCTA, Structure with KEK flanges will
be held pending discussions with KEK.
o Completed one each from deflector structures T11 and T27. They have been installed at
NLCTA for the Echo-7 experiment.
o Worked to produce a T105 accelerator structure: Job submitted, needed machined parts sent
for quotation, mechanical design for the copper is ongoing.
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Novel Structure Designs
o Working on a Mechanical design structure for test of optimized shaped cavity (three cells –
optimized cavity cell and two coupling cells)
o Completed realistic design including initial mechanical design of accelerator cavity geometry
to be used in parallel-fed standing-wave accelerator structure.
o Finalized the design and now manufacturing a cryogenic system to test normal-conducting
accelerating structures at cryo-temperatures are progressing.
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High-Gradient Experiments
o Testing a New PBG structure
o Tested Hard-copper highest-shunt-impedance 1C-SW-A2.65-T2.0-Clamped-Cu-SLAC-#1.
o Tested T18 Structure with a resonant ring
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Accelerator Research Division Quarterly Report – 2001/Q1
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Manufactured and delivered to collaborators:
o Reiterated on hard-copper-cells for advanced coating to Yale.
o Delivered Mode launchers for Argonne National Lab.
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RF Undulators
o Tested RF undulator structure and compared it to simulations with exceptional agreements.
o Designed a new type of end wall termination for the undulator with reduced fields
o Started looking a beam dynamics
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Superconducting Material Research
o Continue testing new stratified media based on MgB2
o Continue testing new Nb samples
o Testing the newly fabricated structure cavity for testing residual resistance.
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Publications
o Roark A. Marsh Michael A. Shapiro, Richard J. Temkin, Valery A. Dolgashev, Lisa L.
Laurent, James R. Lewandowski, A. Dian Yeremian, Sami G. Tantawi, “X-Band Photonic
Bandgap (PBG) Accelerator Structure Breakdown Experiment,” Phys. Rev. ST Accel. Beams
14, 021301 (2011) [11 pages].
o
Lisa Laurent, Sami Tantawi, Valery Dolgashev, Chris Nantista, Yasuo Higashi, Markus
Aicheler, Samuli Heikkinen, and Walter Wuensch, “Experimental Study of RF Pulsed
Heating,” Phys. Rev. ST Accel. Beams – (accepted for publication).
AARD – Plasma Group:
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Worked with TFD to develop an integrated layout of the FACET IP area that accommodates
several experimental groups without the need for removal of experimental hardware between
runs.
Worked with TFD and controls department to experimental protection system (EPS) and
necessary interlocks and controls for the plasma oven.
Worked with beam physics department to develop alternate FACET optics to produce shaped
drive bunches for high transformer ratio PWFA experiments at FACET.
Worked with beam physics department to develop optics multi-knobs to introduce x-z and y-z
correlations on the beam at the plasma entrance to make parametric measurement of the electron
hose instability.
Developed a configuration for installation of a one-meter long x-band deflecting cavity in the
FACET beamline upstream of the IP that provides the required experimental resolution (30 fs)
with existing infrastructure and nominal optics.
Completed SAREC review of FACET proposals – PWFA proposal received the highest possible
rank from the committee (Excellent).
Delivered Two oral presentations, 6 posters and 7 presentations at PAC11 New York.
Hosted FACET satellite meeting at PAC11 with 35 attendees.
AARD – Laser Group:
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NLCTA Beam Tests
o Successfully detected wakefield radiation in 4 different photonic crystal test fibers excited by
the NLCTA electron beam.
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Accelerator Research Division Quarterly Report – 2001/Q1
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A near-IR spectrometer was used to spectrally analyze the radiation from one of the
commercial fibers within the bandgap region, providing first demonstration of e-beam
coupling to TM modes in an optical scale photonic crystal structure.
A Mach-Zehnder Interferometer was adapted for use with a free-space TEM01* mode, with the
intention of measuring phase length dependence on temperature for TM rather than TE fiber
modes. A TM mode was successfully excited and observed.
Designs completed and parts ordered for construction of a tunable optical parametric oscillator
(OPO) to be used for alignment testing of prototype silicon woodpile accelerator structures in the
4 to 5 micron wavelength region.
Silica gratings with the proper aspect ratio and line spacing for 800nm wavelength operation were
successfully fabricated, and techniques were explored for making a spacer layer to separate two
gratings to create a prototype accelerator structure.
Simulations conducted of newly proposed laser-driven dielectric structure for transverse
confinement of electron beams showing successful excitation of focusing fields by an externally
coupled Gaussian laser pulse.
Simulations performed to model various components of coupling schemes for the woodpile
accelerator structure, indicating up to 70% coupling efficiency from free space Gaussian mode to
on-chip silicon waveguides and 95% efficiency for coupling to accelerating channel by a sidecoupled photonic crystal waveguide T-junction.
Publications and Talks:
o Invited Talk at PAC11 Conference, "Experiment to Demonstrate Acceleration in Optical
Photonic Bandgap Structures," R. J. England, et. al.
o E. R. Colby et al., "A Laser-Driven Linear Collider: Sample Machine Parameters and
Configuration," PAC11 proceedings.
o C. M. McGuinness, et al., "Fabrication and Measurement of a Silicon Woodpile Accelerator
Structure," PAC11 proceedings.
o J. E. Spencer, et al., "Coupler Studies for a PBG Fiber Accelerator," PAC11 proceedings.
o K. Soong, et al., "Experimental Determination of Damage Threshold Characteristics of IR
Compatible Optical Materials," PAC11 proceedings.
o R. Laouar, et al., "Measurement of Thermal, Stress, and Field Dependencies of PBG Fiber
Properties," PAC11 proceedings.
o E. Peralta, et al., "Fabrication and Measurement of Silica Grating Accelerator Structures,"
PAC11 proceedings.
o Z. Wu, et al., "Design of On-Chip Power Transport and Coupling Components for a Silicon
Woodpile Accelerator", PAC11 proceedings.
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Accelerator Research Division Quarterly Report – 2001/Q1
AARD – Feedback and Dynamics Group:
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Integration of realistic feedback model into CMAD particle dynamics code - allows evaluation of
instability dynamics, impact of realistic feedback ( bandwidth limits, offsets, noise)
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Testing of 100W 1 GHz amplifiers for upcoming SPS MD - intergration of power stages into 4
GS/sec. excitation system
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LHC MD results focused on longitudinal diffusion from RF system noise
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Sho Uemura ( Stanford Physics) has joined the group as a student RA.
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Publications and Talks:
o
o
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Themis Mastorides presented his contributed talk "Studies of RF Noise Induced Bunch
Lengthening at the LHC", PAC11
Ozhan Turgut, "Estimation of Ecloud and TMCI Driven Vertical Instability Dynamics from
SPS MD Measurements - Implications for Feedback Control”, PAC11
C. Rivetta, J. Fox, T. Mastorides, M. Pivi, O. Turgut, W. Hofle, R. Secondo, J-L. Vay.
"Mathematical Models of Feedback Systems for control of intra-bunch instabilities driven by
E-Clouds and TMCI", PAC11
3. Beam Physics Department
The mission of the Beam Physics Department (BPD) is primarily focused on beam theory. There are three
beam dynamics groups: Collective Effects, FEL Physics, and Beam Optics & Nonlinear Dynamics.
These groups supports the operating accelerators at SLAC and studies beam physics that can enable or
limit future accelerators and its members work closely with other ARD groups and programs. BPD also
contains the Advanced Computation Group. This group develops massively parallel computing
techniques to solve problems in beam physics. It supports accelerator programs at SLAC as well as across
the US. The R&D enables improved understanding of accelerator phenomena through simulation and
allows a cost-effective accelerator design process through extensive calculation.
Collective Effects:
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Daniel Ratner successfully graduated with thesis defense.
Systematic studies of the emittance exchange. A method is proposed to achieve exact phase space
exchange, i.e. mapping x to z, x' to delta, z to x and delta to x'. The work is documented in a
PAC11 proceedings paper.
A triple modulator-chicane scheme for seeding FELs is proposed. The scheme has the advantage
that ultrahigh harmonics can be generated while simultaneously keeping the energy spread
growth much smaller than beam's initial slice energy spread. The paper is submitted to New
Journal of Physics.
Work on noise and coulomb collision effects in the EEHG.
Work continued on ECHO-7 commissioning. The 5th harmonic at 318 nm with the EEHG
technique was observed in January 2011 and in the following months the in-vacuum UV
spectrometer was tested and observed coherent harmonic radiation at 266 nm from the 800 nm
seed laser.
Work on foil emittance partitioning.
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Accelerator Research Division Quarterly Report – 2001/Q1
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Work on CSR calculations using direct numerical solution of Maxwell’s equations.
Work on wakefield calculation in the interaction region of the ILC.
Study dynamic aperture on low emittance (7nm) optics of SPEAR3;
Study of synchrotron oscillation on cross-correlation on the bunch length measurement in
SPEAR3
Study of the beam ion instability in SPEAR3
Principle study on LCLS fs bunch length measurement using ionization electrons
Simulation of electron cloud in CESRTA
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Talks and papers (with abstracts):
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G. Stupakov, K. Bane and I. Zagorodnov. “Impedance scaling for small angle transitions”,
Phys. Rev. ST Accel. Beams 14, 014402 (2011). Abstract: Based on the parabolic equation
approach to Maxwell’s equations, we have derived scaling properties of impedance that
apply either to (1) structures of general shape at high frequencies, or (2) small angle
transitions at all frequencies. Applying these scaling properties to impedance/wakefield
calculation of long, small angle, beam pipe transitions, like one often finds in insertion
regions of storage rings, one can greatly reduce the computer resource required. We have
tested the scaling with wakefield simulations of 2D and 3D models of such transitions, and
have found that it appears to work well.
Michael P. Dunning et al. "Status and Upgrades of the NLCTA for Studies of Advanced
Beam Acceleration, Dynamics, and Manipulation", PAC 2011. Abstract: The Next Linear
Collider Test Accelerator (NLCTA) is a low-energy electron accelerator (120 MeV) at SLAC
that is used for ultra-high gradient X-band RF structure testing and advanced accelerator
research. Here we give an overview of the current program at the facility, including the E163 direct laser acceleration experiment, the echo-enabled harmonic generation (EEHG)
FEL experiment, narrow-band THz generation, coherent optical transition radiation (COTR)
studies, microbunching instability studies, and X-band structure testing. We also present the
upgrades that are currently underway and some future programs utilizing these upgrades,
including extension of the EEHG experiments to higher harmonics, and an emittance
exchange experiment.
Dao Xiang et al. "Experimental Demonstration of the Echo-enabled Harmonic Generation
Technique for Seeded FELs", PAC 2011. Abstract: Recently the scheme of echo-enabled
harmonic generation (EEHG) was proposed for short wavelength seeded FELs. This scheme
allows far higher harmonic numbers to be accessed and makes the generation of coherent
soft x-ray directly from a UV seed laser in a single stage possible. In this paper we present
the experimental demonstration of this echo harmonic technique at the Next Linear Collider
Test Accelerator (NLCTA) at SLAC, where the coherent radiation at the harmonic frequency
of the seed laser is generated using the 120 MeV electron beam. The experiment confirms the
physics behind this technique and paves the way for applying it for seeded x-ray FELs.
B. Podobedov and G. Stupakov. "Calculating Point-Charge Wakefields from Finite Length
Bunch Wake-Potentials", PAC 2011. Abstract: Starting from analytical properties of high
frequency geometric impedance we show how one can accurately calculate short bunch
wake-potentials (and even point-charge wakefields ) from time domain calculations
performed with a much longer bunch. In many practical instances this drastically reduces the
need for computer resources, speeds up the calculations, and improves their accuracy. To
illustrate this method we give examples for accelerator structures of various complexities in
both 2D and 3D.
A. Novokhatski. "CSR Fields from using a Direct Numerical Solution of Maxwell's
Equations", PAC 2011. Abstract: Using a previously developed method to numerically
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Accelerator Research Division Quarterly Report – 2001/Q1
o
calculate electromagnetic fields of very short bunches we simulate coherent synchrotron
radiation (CSR) in a rectangular bending magnet vacuum chamber. Initial results clearly
show the first part of the CSR - magnet edge radiation. The transverse shape of this part
looks very similar to the screen images, seen after the dump magnets at the SLAC LCLS. As
an ultra-relativistic bunch and the CSR fields have almost the same propagation velocity they
essentially move together and interact for a long time until the bunch goes into another beam
chamber. The CSR edge radiation part continues to propagate straight ahead.
A. Novokhatski. "Wake Potentials in the ILC Interaction Region", PAC 2011. Abstract: The
vacuum chamber of the ILC Interaction Region (IR) is optimized for best detector
performance. It has special shaping to minimize additional backgrounds due to the metal part
of the chamber. Also, for the same reason this thin vacuum chamber does not have water
cooling. Therefore, small amounts of power, which may be deposited in the chamber, can be
enough to raise the chamber to a high temperature. One of the sources of “heating” power is
the electromagnetic field of the beam. We will consider three ways in which power can be
transferred from the beam. They are: image current losses, losses due to propagating wake
fields, which stay for a short time in the IR and losses from trapped modes, which may stay
for a long time. To calculate these effects we use analytical formulas; wake field code NOVO
and Eigen mode calculations with MAFIA.
FEL Physics:
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Finalized LCLS-II CDR and prepared for CDR review.
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A single-shot electron bunch length measurement technique has been tested on the LCLS with ~1
fs resolution achieved.
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A new method is developed to measure the ultra-short soft x-rays pulse length through the
analysis of the statistical properties of the SASE FEL spectra. The method has been
experimentally demonstrated at LCLS. Different x-ray bunch lengths have been measured
keeping the electron bunch charge fixed at 250 pC and manipulating the peak current from 1.5 kA
to 3kA. Bunch length has been also measured for different number of undulators. Finally using
the slotted foil to obtain shorter pulses, x-ray pulse lengths down to 13 fs FWHM have been
measured.
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Investigated the use of x-band deflector to measure single-shot fs electron and x-ray pulse
duration that is applicable to wide operating conditions.
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Worked on optimizing the undulator tapering in a self-seeding scheme to reach terawatts (TW)
FEL for LCLS-II. Empirical solution to have a TW FEL is found to be feasible within the planned
upgrade scheme for the LCLS-II undulator system. Analytical estimate and simulation code
development within Genesis are ongoing.
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Studied the scheme of introducing density modulation on the electron bunch before it enters the
undulator. The density modulation period has been compressed to nm level to generate coherent
soft X-rays.
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Developed a general 3D FEL theory when the transverse beam size varies in the undulator.
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Accelerator Research Division Quarterly Report – 2001/Q1
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Paper published or submitted:
o
“GENERATION OF COHERENT X-RAY RADIATION THROUGH MODULATION
COMPRESSION” Ji Qiang (LBL), J. Wu, Nuclear Instruments and Methods A,
2011.03.020. Abstract: In this paper, we propose a scheme to generate tunable coherent
X-ray radiation for future light source applications. This scheme uses an energy chirped
electron beam, a laser modulator, a laser chirper and two bunch compressors to
generate a prebunched kilo-Ampere current electron beam from a few tens Ampere
electron beam out of a linac. The initial modulation energy wavelength can be
compressed by a factor of 1+hbRa56 in phase space, where hb is the energy bunch
length chirp introduced by the laser chirper, Ra56 is the momentum compaction factor of
the first bunch compressor. As an illustration, we present an example to generate more
than 400 MW, 170 attoseconds pulse, 1 nm coherent X-ray radiation using a 60 A
electron beam out of the linac and 200 nm laser seed. Both the final wavelength and the
radiation pulse length in the proposed scheme are tunable by adjusting the compression
factor and the laser parameters.
o
“MEASUREMENT OF FEMTOSECOND LCLS BUNCHES USING THE SLAC ALINE SPECTROMETER” Z. Huang et al., PAC2011 proceedings. Abstract: We
describe a novel technique and the preliminary experimental results to measure the
ultrashort bunch length produced by the LCLS low-charge, highly compressed electron
bunch. The technique involves adjusting the LCLS second bunch compressor followed by
running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result,
the time coordinate of the bunch is directly mapped onto the energy coordinate at the end
of the linac. A high-resolution energy spectrometer located at an existing transport line
(A-line) is then commissioned to image the energy profile of the bunch in order to
retrieve its temporal information. We present measurements of the single-digit
femtosecond LCLS bunch length using the A-line as a spectrometer and compare the
results with the transverse cavity measurement as well as numerical simulations.
o
“TECHNICAL CHALLENGES IN THE LINAC COHERENT LIGHT SOURCE,
COMMISSIONING AND UPGRADES” J. Galayda, Z. Huang et al, invited talk at
PAC2011. Abstract: Five months after first lasing in April 2009, the Linac Coherent
Light Source (LCLS) began its first round of x-ray experiments. The facility rapidly
attained and surpassed its design goals in terms of spectral tuning range, peak power,
energy per pulse and pulse duration. There is an ongoing effort to further expand
capabilities while supporting a heavily subscribed user program. The facility continues to
work toward new capabilities such as multiple-pulse operation, pulse durations in the
femtosecond range, and production of >16 keV photons by means of a second-harmonic
“afterburner” undulator. Future upgrades will include self-seeding and polarization
control. The facility is already planning to construct a major expansion, with two new
undulator sources and space for four new experiment stations.
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Accelerator Research Division Quarterly Report – 2001/Q1
Advanced Computation Group
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Three talks were given in PAC11, including an invited talk about the simulation of the two-beam
acceleration system.
o
Invited talk: “NUMERICAL VERIFICATION OF THE POWER TRANSFER AND
WAKEFIELD COUPLING IN THE CLIC TWO-BEAMACCELERATOR” A. Candel, Z.
Li, C. Ng, V. Rawat, G. Schussman and K. Ko, SLAC I. Syratchev, A. Grudiev and W.
Wuensch, CERN Abstract: The Compact Linear Collider (CLIC) provides a path to a multiTeV accelerator to explore the energy frontier of High Energy Physics. Its two-beam
accelerator (TBA) concept envisions complex 3D structures, which must be modeled to high
accuracy so that simulation results can be directly used to prepare CAD drawings for
machining. The required simulations include not only the fundamental mode properties of the
accelerating structures but also the Power Extraction and Transfer Structure (PETS), as well
as the coupling between the two systems. Time-domain simulations will be performed to
understand pulse formation, wakefield damping, fundamental power transfer and wakefield
coupling in these structures. Applying SLAC’s parallel finite element code suite, these largescale problems will be solved on some of the largest supercomputers available. The results
will help to identify potential issues and provide new insights on the design, leading to further
improvements on the novel two-beam accelerator scheme.
o
“High Fidelity Calculation of Wakefields for Short Bunches” C.-K. Ng, A.E. Candel, K. Ko,
V. Rawat, G.L. Schussman, L. Xiao, SLAC, Menlo Park, California. Abstract: The
determination of wakefields for short bunches in accelerator structures with complex
geometries and large spatial dimensions requires significant computational resources. The
time domain code T3P developed at SLAC employs the higher-order finite element method for
high fidelity modeling and parallel computation for large-scale simulation on state-of-the-art
supercomputers. To facilitate wakefield calculation for short bunches, T3P has been
enhanced through the implementation of a moving window technique which reduces
computing resource requirements by orders of magnitude. For local refinement in the moving
window, both a finer unstructured mesh and higher-order finite element basis functions can
be employed. Applications demonstrating the efficacy of the technique include wakefield
calculations of shallow tapers in storage rings, complex and long vacuum chamber
transitions in energy recovery linacs (ERL) and higher-order-mode (HOM) couplers in
superconducting rf cavities.
o
“On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams”, Zenghai
Li, Feng Zhou, Arnold Vlieks and Chris Adolphsen, SLAC. Abstract: The input power of
accelerator structure is normally fed through a coupling slot(s) on the outer wall of the
accelerator structure via magnetic coupling. While providing perfect matching, the coupling
slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance
growth as the beam is accelerated in such a field. This effect is especially important for low
emittance beams at low energies such as in the injector accelerators for light sources. In this
paper, we present studies of multipole fields of different rf coupler designs and their effect on
beam emittance for an X-band photocathode gun, being jointly designed with LLNL, and the
X-band accelerator structures. We will present symmetrized rf coupler designs for these
components to preserve the beam emittance.
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Accelerator Research Division Quarterly Report – 2001/Q1
Beam Optics & Non-Linear Dynamics
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We have completed the ERL configuration study. The results of the study were documented in
two papers presented in the PAC 11.
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We continued to design an ultimate storage ring based on the PEP tunnel. Since the last report,
we have added damping wigglers to reduce the equilibrium emittance further down to 15 pm-rad .
Emittance growth due to the intra-beam scattering was about a factor of two at 200 mA beam
current. This extremely low emittance makes the Touschek lifetime much longer than one hour.
That is significant improvement from the baseline design. Currently, we are optimizing the
dynamic aperture of the lattice.
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Publications and Talks
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R. Hettel et al. "Status of the PEP-X Light Source Design Study", PAC 2011. Abstract: The
SLAC Beam Physics group and collaborators continue to study options for implementing a
near diffraction-limited ring-based light source in the 2.2-km PEP-II tunnel that will serve
the SSRL scientific program in the future. The study team has completed the baseline design
for a 4.5-GeV storage ring having 160-pm-rad emittance with stored beam current of 1.5 A,
providing >1022 brightness for multi-keV photon beams from 3.5-m undulator sources. The
team is now investigating possible 5-GeV ERL configurations which, similar to the Cornell
and KEK ERL plans, would have ~30 pm-rad emittance with 100 mA current, and ~10 pmrad emittance with 25 mA or less. In the next year, a diffraction-limited storage ring using
on-axis injection in order to reach 30 pm-rad or less emittance will be investigated. An
overview of the PEP-X design study and SSRL’s plans for defining the performance
parameters that will guide the choice of implementation options is presented.
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“OPTICS TUNING KNOBS FOR FACET” Y. Nosochkov, M.J. Hogan, W. Wittmer:
Abstract: FACET is a new facility under construction at the SLAC National Accelerator
Laboratory. The FACET beam line is designed to provide 23 GeV tightly focused and
compressed electron and positron bunches for beam driven plasma wakefield acceleration
research and other experiments. Achieving optimal beam parameters for various
experimental conditions requires the optics capability for tuning in a sufficiently wide range.
This will be achieved by using optics tuning systems (knobs). Design of such systems for
FACET is discussed.
o
“LATTICE DESIGN FOR ERL OPTIONS AT SLAC” Y. Nosochkov, Y. Cai, X. Huang,
M.-H. Wang: Abstract: SLAC is investigating long-range options for building a high
performance light source machine while reusing the existing linac and PEP-II tunnels. One
previously studied option is the PEP-X low emittance storage ring. The alternative option is
based on a superconducting Energy Recovery Linac (ERL) and the PEP-X design. The ERL
advantages are the low beam emittance, short bunch length and small energy spread leading
to better qualities of the X-ray beams. Two ERL configurations differed by the location of the
linac have been studied. Details of the lattice design and the results of beam transport
simulations with the coherent synchrotron radiation effects are presented.
o
“COMPENSATION OF DETECTOR SOLENOID IN SUPER-B” Y. Nosochkov, K.
Bertsche, M. Sullivan. Abstract: The SUPER-B detector solenoid has a strong 1.5 T field in
the Interaction Region (IR) area, and its tails extend over the range of several meters. The
main effect of the solenoid field is coupling of the horizontal and vertical betatron motion
11
Accelerator Research Division Quarterly Report – 2001/Q1
which must be corrected in order to preserve the small design beam size at the Interaction
Point. The additional effects are orbit and dispersion caused by the angle between the
solenoid and beam trajectories. The proposed correction system provides local compensation
of the solenoid effects independently for each side of the IR. It includes “bucking” solenoids
to remove the solenoid field tails and a set of skew quadrupoles, dipole correctors and antisolenoids to cancel linear perturbations to the optics. Details of the correction system are
presented.
o
“FACET Emittance Growth” J. Frederico, M. J. Hogan, Y. Nosochkov, M. Litos, T.
Raubenheimer. Abstract: FACET, the Facility for Advanced Accelerator and Experimental
Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study
beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and
final focus system to compress the 23 GeV, 3.2 nC electron bunches to ~20 micrometer long
and ~10 micrometer wide. Simulations of the FACET beamline indicate the short-duration
and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from
a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent
synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in
plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of
the geometric, CSR, and ISR components are presented. Numerical calculation of the rms
emittance can be overwhelmed by long tails in the simulated phase space distributions; more
useful definitions of emittance are given. A complete simulation of the beamline is presented
as well, which agrees with design specifications.
o
“SYNCHROTRON LIGHT OPTIONS AT SUPER-B” Walter Wittmer, Yuri Nosochkov,
Alexander Novokhatski, John Seeman, Michael K. Sullivan (SLAC), Maria Enrica Biagini,
Pantaleo Raimondi (INFN/LNF). Abstract: The Super-B facility will collide electron and
positron beams with different characteristics as done in the past at PEP-II and KEKB. The
ring and electron (positron) beam characteristic of both high and low energy rings of the
Super-B are comparable to NSLS-II and other state of the art synchrotron light sources. This
suggests the use of this facility, either parasitically or in dedicated runs, as light source. In
this paper we compare the characteristics of the synchrotron light generated at Super-B with
existing, in construction and proposed facilities. We investigate different schemes to
incorporate the generation of synchrotron radiation in the collider lattice design and look at
different beam line layouts for users.
o
“SUPERB: THE NEXT-GENERATION e+e- B-FACTORY COLLIDER” W. Wittmer, A.
Novokhatski, K. Bertsche, Y. Nosochkov, J. Seeman, M. K. Sullivan, U. Wienands (SLAC),
A.V. Bogomyagkov, E. Levichev, S. Nikitin, P. Piminov, D. Shatilov, S. Sinyatkin, P. Vobly,
I.N. Okunev (BINP), B. Bolzon, L. Brunetti, A. Jeremie (IN2P3 LAPP), M.E. Biagini, R.
Boni, M. Boscolo, T. Demma, A. Drago, M. Esposito, S. Guiducci, S. Liuzzo, M. Preger, P.
Raimondi, S. Tomassini, M. Zobov, E. Paoloni, P. Fabbricatore, R. Musenich, S. Farinon
(INFN/LNF), S. Bettoni (CERN), F. Poirier, C. Rimbault, A. Variola (LAL), M. Baylac, O.
Bourrion, N. Monseu, C. Vescovi (LPSC), A. Chanc (CEA). Abstract: The SuperB
international team continues to optimize the design of an electron-positron collider, which
will allow the enhanced study of the origins of flavor physics. The project combines the best
features of a linear collider (high single-collision luminosity) and a storage-ring collider
(high repetition rate), bringing together all accelerator physics aspects to make a very high
luminosity of 10^36 cm^-2 sec^-1. This asymmetric-energy collider with a polarized electron
beam will produce hundreds of millions of B-mesons at the upsilon(4S) resonance. The
present design is based on extremely low emittance beams colliding at a large Piwinski angle
to allow very low betay. without the need for ultra short bunches. Use of crab-waist
sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a
12
Accelerator Research Division Quarterly Report – 2001/Q1
higher beam-beam parameter. The project has flexible beam parameters, improved dynamic
aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the
electron beam at the Interaction Point. Optimized for best colliding-beam performance, the
facility may also provide high-brightness photon beams for synchrotron radiation
applications.
4. Accelerator Design Department
The Accelerator Design Department (ADD) is focused on the design of normal conducting and
superconducting linear colliders and the development of the required technology. In addition, the
department investigates applications of these technologies that may enable other facilities such as
Project-X as well as other SLAC facilities. This R&D is aimed at a next generation TeV-scale
linear collider but may have application to compact light sources, industrial and medical
accelerators.

ILC Systems R&D:
o
In FY11, about 20 SLAC physicists attended the IWLC meeting in Geneva in October, and
12 SLAC physicists attended the ALCPG meeting in Eugene in March. They also attended
meetings of the IDAG and AAP and participated in the change control review process.
o
Electron Source: The group received the KMLabs laser produced under an SBIR at the end of
Q1. A pair of 18W, 515 nm pump lasers will be incorporated into the final stage amplifier of
the KMLabs system to increase the laser output to 3 MHz.
o
Damping Rings: The electron cloud Working Group gave a preliminary recommendation for
ecloud mitigation in Q1. The WG is now preparing a detailed report due by early 2012.
There was also work on the 3.2 km damping ring design, including optics, dynamic aperture
and simulations to assess the impact of reducing the bunch spacing to 3ns. For the CesrTA
program, there was continued work on ecloud build-up simulations and on instability
simulations. This work will be part of the CesrTA phase I report.
o
Accelerator Physics: In FY11, this has mainly involved studies related to the proposed costsaving changes to the baseline design that impact the linacs. In particular, studies were done
on the (1) rf overhead needed to accommodate the ~ 20% spread in sustainable cavity
gradients, (2) configuration of the KCS and RDR rf distribution systems for operation with
half the number of bunches per pulse and (3) operation at higher repetition rates at lower
beam energies, in particular, running at 10 Hz with 125 GeV per beam ‘collision’ pulses
interleaved with 150 GeV electron beam pulses that produce positrons at the end of the
electron linac.
o
Machine Detector Interface: The MDI group continued to study the performance of a
platform-based support for the SiD detector and concluded that such a solution was indeed
allowable, given the inter-bunch feedback system. A document “Functional Requirements of
a SiD Platform” was presented at the ALCPG meeting in Eugene Oregon in March 2011.
Progress on this front was labeled one of the most significant accomplishments of the
meeting.
13
Accelerator Research Division Quarterly Report – 2001/Q1
An analysis of HOM induced heating near the IP was completed and presented at the
ALCPG, taking into account the detailed engineering design of the beam pipe in the 7m
surrounding the interaction point. For the ILC bunch structure and bunch length, neither
trapped mode nor resistive wall heating appears to be a problem.
The paperwork required to transfer funds to the University of Michigan to develop a
frequency scanning interferometer based alignment system was completed. Results from new
hardware should be available by the time of the next report.
o
ATF2 Test Facility : At least 2 members of the SLAC ATF2 team participated in all beam
operations during January – March 2011. Beam operations stopped March 11 due to the M9.0
earthquake in Eastern Japan; we expect full operations to commence again from fall, 2011,
after reconstruction and realignment work is completed. There was an ATF2 collaboration
meeting at SLAC in January to discuss progress towards the main ATF2 goals.
The targets on the 4 OTR systems were replaced with Al and Aluminized Kapton targets. The
OTR system is now fully operational and routinely used during tuning operations with a
measurement time of <2 mins (compared with many hours with the wirescanner system).
SLAC is taking a leading role in the development of the readout system for the IP region
cavity BPMs which need to read out the position of the electron beam at the IP waist to very
high precision; ideally <2nm vertically. This will be based on the SLAC digitizer boards
developed for LCLS BPMS
SLAC has worked together with magnet engineers at KEK to now have an accurate computer
model of the ATF2 beamline including a precise description of the measured sextupole and
octupole fields in all the ATF2 magnets. This data will be used to optimize the ATF2 optics
to account for these fields and develop a new magnetic configuration of the machine for
future runs.
o
Ultra-fast ATF2 Extraction Kicker: Progress has been made on demonstrating a new
topology to eliminate the pre-pulse and there was a brassboard circuit demonstration of the
output pulse. A vendor to fabricate a second generation hybrid has been identified and a
conceptual design for an ultra-fast discrete component driver developed.
o
High Availability Controls: The Marx P2 interlock design requirements, design and prototype
fabrication are complete except for high level software. The companion analog Rear
Transition Module board is designed and beginning layout.
The major labs in the MicroTCA Standards collaboration now include CERN, DESY, FNAL,
IHEP, IPFN, ITER, LBNL and SLAC, with ESSB (European Spallation Neutron Source
Bilbao) in process of joining. Standards are being reviewed for the MicroTCA extension now
known as PICMG MTCA.4, for the Rear Transition Module (RTM) interface ATCA
PICMG3.8, and on a guideline for a distribution system for precise timing and triggers on the
large-system backplane. The operating system under Linux is developed and operational
including hot-swap capability. MicroTCA was proposed both for the RF and main linac
upgrades needed for LCLS I&II and future experiments using the linac.
14
Accelerator Research Division Quarterly Report – 2001/Q1

ILC RF system: The SLAC effort is focused mainly on developing lower cost and more reliable
rf components for the main linacs. Areas of research include:
o
Marx Modulator: The P1 Marx backplane was replaced with a more robust version to reduce
corona damage. Also, the P1 Marx continued operation 24/7 at half pulse width while the
capacitor lifetime problem was being studied in a separate test stand. During the > 1000 hours
of operation of the P1 at this narrower pulse width, there have been few faults and no
measureable loss of capacitance. All of the major components for the P2 Marx have been
purchased, and the upgrade of DTI Marx has started.
o
Global RF Distribution: The windows and some of the rectangular waveguide were upgraded
on the 10 m ‘Big Pipe’ section. It recently ran for over 100 hours with no breakdown at 265
MW (at the 280 MW design power, there is a breakdown every few hours). With HEEC
approval, the pipe pressure will be increased from 15 psig to at least 18 psig to see if this
allows for stable operation at higher power. For Phase II of this project, requests for bids for
80 m of new pipe (rated for 30 psig) were placed and a preliminary design completed for a
support system to mount the pipe. Also, the rf design for the required 90 degree waveguide
bend is nearly complete.
o
Local RF Distribution: A second generation, 8-feed, variable power rf distribution system is
being built for FNAL’s second cryomodule. This version has remote-controlled phase shifters
to adjust the power split among the cavities. The first two- feed sub-unit has been cold tested
and will be high power tested soon.
o
Couplers: Two failed cold coupler sections returned to SLAC by FNAL were extensively
examined. These couplers had been returned to CPI for repair after initial inspection at
SLAC, and their resulting ‘fixes’ seem to have caused damage that lead to subsequent
breakdown and copper removal problems at FNAL when they were eventually used to power
SC cavities. Currently, the issue of copper particles coming loose during ultrasonic cleaning
of the copper plated couplers is be examined. For this purpose, various samples (pure copper,
CPI plated copper with and without bead blasting, and SLAC-plated copper) are being
ultrasonically cleaned and the number of copper particles that come loose are being
measured.
o
For the ILC Electron Sources, a Kapteyn-Murnane Laboratories (KMLabs) ILC laser was
shipped to SLAC in Q1 FY11. This laser system was developed by KMLabs under a SBIR
Phase II proposal. Prior to shipment, this laser was observed to produce a full energy ILC
source laser pulse train at 1.5 MHz. A pair of 18W, 515 nm pump lasers will be incorporated
into the final stage amplifier of the KMLabs system to increase the laser output to 3 MHz.
The plan developed in conjunction with JLab to demonstrate an ILC specification source
beam at SLAC in FY11 and then at JLab in FY12 has been modified. SLAC will continue
with the ILC source laser development while JLab continues development of a high voltage,
high gradient ILC dc photogun. It has been agreed that SLAC will take the lead in the writing
of the Electron Source chapter for the ILC Technical Design Report.
o
For the ILC Damping Rings, SLAC is coordinating the international Working Group on the
electron cloud R&D. The Working Group gave a preliminary recommendation for the
electron cloud mitigation in October and it is now preparing a detailed report document due
by early 2012. In collaboration with INFN Frascati, we worked on the DR optics and on the
dynamic aperture for the selection of a baseline 3.2 km damping ring design to be included in
the TDR-II. For the CesrTA program, we worked on build-up simulations for quadrupole
15
Accelerator Research Division Quarterly Report – 2001/Q1
and wiggler regions and worked on instability simulations to include radiation damping and
more realistic electron cloud distributions over the CesrTA ring. This work will be part of the
CesrTA Phase I report.
o
For the ILC Machine Detector Interface (MDI) in FY11-Q2, seven MDI meetings took place
and the results were presented at the ALCPG meeting in Eugene, Oregon in March 2011.
Details of the weekly meetings are available at
http://ilcagenda.linearcollider.org/categoryDisplay.py?categId=188.
At the ALCPG meeting the SiD collaboration committed itself to the concept of using a
platform to accomplish push pull operations with the ILD detector. A list of functional
requirements for the platform was developed and presented as input to the ILC Conventional
Facilities group, who are responsible for the detailed engineering of the system. Work
continued on measuring the vibration properties of various concrete blocks to validate the
analysis models, a Frequency Scanning Interferometry (FSI) based alignment system, a reevaluation of SR backgrounds, and an analysis of HOM induced heating near the IP. A grant
request by U. Michigan for FSI work that was submitted to SLAC was finalized.

FNAL Project X: SLAC received 400 k$ in PX funding from FNAL for FY11. It will be used in
part to study possible 650 MHz, 30 kW rf sources for the PX CW linac, in particular, to examine
solid state sources, which are becoming cost competitive with IOTs. Recently, two US vendors
provided cost estimates for 30 kW and 2 kW 650 MHz solid state sources. For the 3-8 GeV PX
pulsed linac, possible long pulse (up to 25 ms) klystrons and modulators will be examined –
currently design and cost studies of Marx modulators for this application are being done.

X-Band: The SLAC X-band program includes testing CLIC prototype structures, developing and
testing a Dual Mode Cavity to better understand breakdown limitations, developing an X-band
gun (with LLNL) and associated test beamline (XTA), upgrading the X-band systems at NLCTA
in support of other programs there, developing X-band linac designs for light source applications
and designing a more robust 50 MW XL4 klystron. Progress is summarized below.
o
CLIC: The T24 structure was operated for an additional 100 hours longer but no
improvement in breakdown rate was observed. The TD24 structure was assembled using cells
provided by KEK, and will be tested next.
o
Dual Mode Cavity: Stn 1 and Stn 2 were configured to power the two cavity modes
independently. The results showed that the breakdown rate increased significantly for a fixed
surface electric field when the pulsed heating from the TE mode was increased above about
50 degC. These results were presented at PAC11.
o
X-band Gun: Construction was started for the 5.59 cell X-band gun (Mark 1) and assembly
was completed of a partially fabricated gun (the 5.5 cell Mark 0) from an earlier project. This
latter gun will be tested without beam in ASTA in FY11-Q3 to measure breakdown rates and
dark currents. At LCLS, studies were done to improve the bunch emittance from their S-band
gun by using a truncated-Gaussian-shaped laser pulse.
o
XTA: A new beamline in NLCTA (called XTA) is being constructed to test X-band rf guns.
The design for this beamline is nearly complete, a number of the parts have been ordered and
the control system, which will use many of the data acquisition modules developed for LCLS,
has been mostly defined.
16
Accelerator Research Division Quarterly Report – 2001/Q1

o
NLCTA Upgrades: The spectrometer magnet bend angle was increased (from 12 to 30
degrees) to improve resolution. Also, the fabrication of two deflecting cavities was completed
and waveguide and other rf components (e.g., phase shifters and loads) that will power them
from Stn 1 and Stn 3 were prepared.
o
Light Sources: For an all-X-band linac, bunch energy linearization can be achieved using the
T566 component of the first bunch compressor chicane if higher harmonic rf is not available.
Several options for such a linearization system were simulated and shown to provide high
current bunches similar to those in LCLS.
o
Linac Optimization: A study was completed of optimized S, C and X-band TW structures for
the cases of short (50 ns) and long (1250 ns) bunch train operation with low beam loading.
The latter case is applicable to the proposed MaRIE project at LANL (they visited SLAC and
we visited LANL this Quarter to discuss this project). The results show that X-band has the
advantage of providing a higher gradient with equal (long pulse) or higher (short pulse) rf-tobeam efficiency. This work was presented in an invited talk at PAC11.
o
XL4 Klystron: A program was started to design a longer (6 cell vs 4 cell) output section for
the XL4 klystron with the goal reducing the surface fields by about 15% - this will hopefully
lead to more robust operation of the tube at 50 MW. A design has been completed and
currently studies are underway to see if other modes will be excited by the beam.
LARP: For the collimator project in FY11 Q2, we:
o
Finished the final rotation tests of the 20-sided rotatable collimator jaws in test mode. Test
mode means that the jaws were free to rotate without their cooling tubes attached to fixed
points and forced to wind up during rotation. The baseplate with now welded steel jaw
supports was lowered onto the two jaws while they rested on a granite table. The jaws were
attached with the final version of the rotation bearing housing, nuts and spacers. The final
versions of the rotation drives, anti-backlash pawl assemblies, rhodium coated RF "wipers",
BeCu RF foils and thermistors holders were attached to the jaw ends. These last 3 items are
designed to provide 0.1 mOhm resistance between the jaw surface and the end of the vacuum
tank for each rotation of the jaw. This was tested and after considerable tuning, achieved. The
post which holds the claw that actuates the rotation mechanism was welded to the baseplate.
The jaw translation drive mechanism was checked for limits of travel and limit switches and
various hard stops tuned for proper interaction with the actuator. The rotation actuation was
reconfirmed under load. A fixture to rotate the entire assembly in phi was designed, built &
installed. This allowed us to put the baseplate in the correct position for each test in a very
safe and controlled manner. At this point everything was disassembled. Each end of each
facet of each jaw had 3 lines scribed to allow for optical alignment through ports in the
vacuum vessel and the jaw facets numbered with a punch. The cooling tubes coming out of
the collimator jaws were carefully bent to 90 degrees.
o
Completed final assembly and rotation tests in a mode where the tubes must be twisted during
rotation (and thus the number of such tests are limited). The baseplate was lowered onto the
jaws for a final time capturing the cooling tubes through minimal clearance feedthroughs in
the baseplate. The jaws were reattached to their moveable supports with the bearing housings
and then the unit rotated to its normal orientation of jaws up, baseplate down. The housings
were tack welded in place. The rotation drives and pawls were remounted. The RF foils and
thermistor holders with thermistors were attached and functioning verified. The first rotation
test with tube twist was performed; alignment was excellent before and after; gear
17
Accelerator Research Division Quarterly Report – 2001/Q1
functioning was flawless. Resistance measurements were as before. Then the molybdenum
rotation housing was tack welded via steel support wire to prevent any future movement and
its mounting screws welded to each other with a thin steel plate. The actuator claw was tack
welded to its support post. A second pair of rotation tests were performed successfully and
the decision to place the unit inside its vacuum vessel was made.
o
Welded the vacuum tank to the baseplate and leak checked, sealing the cooling tube
penetrations with 4 cylinder-covers equipped with O-rings. Leak rates of 1e-10 mbar-l/sec
were achieved. The rest of the period was spent arranging for someone to do the copper tubecopper feedthrough TIG brazes.
o
Other LARP efforts: A wide-band feedback system is proposed to stabilize intra-bunch
instabilities driven by electron-clouds or transverse mode coupling (TMCI) in the CERN
SPS. In support of this project, SLAC has started to work on incorporating into the C-MAD
code a detailed and realistic model of the intra-bunch feedback system to analyze its impact
on the beam emittance and stability. The objective is to simulate the feedback control by
using 16 samples per bunch to process the feedback algorithm, which is equivalent to a 2.6
Giga-Samples/sec sampling frequency in the ADC/DACs and processing channel, which is at
the limit of the available technology. With a realistic model of the hardware, it will be
possible to design a feedback system suitable for suppressing electron cloud and TMCI.
A grooved insert has been installed into in a dedicated test area of the CERN SPS beam line.
We received the preliminary results of short tests made in March. The measured electron
cloud current signal for the grooved insert was a factor of 2 to 15 lower, depending on the
beam parameters, than a reference smooth metallic surface of the same material.

SuperB: No further work was done on the Super-B project pending direction from the DOE.

End Station A: We (Mauro Pivi and the Test Facilities Department) are working on reestablishing the End Station A Test Beam (ESTB) at SLAC. A small fraction of the 13.6 GeV
electron bunches from the Linac Coherent Light Source (LCLS) will provide test beam
capabilities in the large End Station A (ESA) experimental hall for accelerator instrumentation
tests, accelerator R&D, particle and particle astrophysics detector research, linear collider
machine and detector interface studies, radiation-hard detector development and material damage
studies.
Currently the plan includes the installation of one kicker magnet with a stainless steel chamber in
the Beam Switch Yard during Spring 2011. This will allow early commissioning of the kicker
system with the bunches deflected into a beam line upstream of End Station A. As soon as a new
Personal Protection System for ESA is completed later this summer, and a new beam dump is
installed in ESA, a low energy beam will be run into ESA to start commissioning of the complete
test beamline. In late October, we will install four new kicker magnets with ceramics chambers
(to reduce eddy currents) in the Beam Switch Yard and start operating the ESTB at higher beam
energy in November.
In March, we hosted the first ESTB Workshop, which attracted 50 attendees from 16 outside
institutions, underlining the broad interest by the community for a beam test facility. Ahead of the
workshop, we received eight proposals with requests for beam time.
18
Accelerator Research Division Quarterly Report – 2001/Q1

Publications
o
M.A. Kemp, A. Benwell, C. Burkhart, R. Larsen, D. MacNair, M. Nguyen, J. Olsen, “Design
of the second-generation ILC Marx modulator,” LINAC10.
o
M.A. Kemp, A. Benwell, C. Burkhart, J. Hugyik, R. Larsen, K. Macken, D. MacNair, M.
Nguyen, J. Olsen, “The ILC P2 Marx and application of the Marx topology to future
accelerators,” PAC11.
o
David MacNair, Mark A. Kemp, Koen Macken, Minh N. Nguyen, Jeff Olsen, “SLAC P2
Marx control system and regulation scheme,” PAC11.
o
K.J.P. Macken, D. MacNair, M.N. Nguyen, J. Hugyik, J. Olsen, and M. Kemp, “IGBT PEBB
technology for future high energy physics machine operation applications,” APEC2011.
o
Faya Wang, “Design and Optimization of Future X-Ray FELS Based on Advanced High
Frequency Linacs,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A.,
March 28–April 1, 2011.
o
Novokhatski et al., “SuperB: Next-Generation e+e- B-factory Collider,” presented at the 2011
Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
S. Novokhatski, “Wake potentials in the ILC interaction region”, PAC2011, SLAC-PUB14260
o
K.J. Bertsche et al., “Vibration Budget for SuperB,” presented at the 2011 Particle Accel.
Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
Y. Nosochkov et al., “Compensation of Detector Solenoid in SUPER-B,” presented at the
2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
Lisa Laurent et al., “Experimental Study of RF Pulsed Heating,” Phys. Rev. ST - Accel.
Beams, vol. 14, 041001 (2011), April 2011, 21 pp.
o
Faya Wang, Chris Adolphsen, and Christopher Nantista, “Performance Limiting Effects in XBand Accelerators,” Phys. Rev. ST - Accel. Beams, vol. 14, 010401 (2011), January 2011, 5
pp.
o
Faya Wang, Chris Adolphsen, and Christopher Nantista, “Initial High-Power Test Results of
an X-Band Dual-Moded Coaxial Cavity,” presented at the 2011 Particle Accel. Conf.
(PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
M.P. Dunning et al., “Status and Upgrades of the NLCTA for Studies of Advanced Beam
Acceleration, Dynamics, and Manipulation,” presented at the 2011 Particle Accel. Conf.
(PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
S.G. Anderson et al., “An Optimized X-band Photoinjector Design for the LLNL MEGa-Ray
Project,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March
28–April 1, 2011.
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Accelerator Research Division Quarterly Report – 2001/Q1
o
R.A. Marsh et al., “X-Band RF Photoinjector Research and Development at LLNL,”
presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1,
2011.
o
T.L. Houck et al., “50 MW X-Band RF System for a Photoinjector Test Station at LLNL,”
presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March 28–April 1,
2011.
o
Z. Li et al., “On the Importance of Symmetrizing RF Coupler Fields for Low Emittance
Beams,” presented at the 2011 Particle Accel. Conf. (PAC’11), New York, U.S.A., March
28–April 1, 2011.
o
F.V. Hartemann et al., “Overview of Current Progress on the LLNL Center for Nuclear
Photonics and Mono-energetic Gamma-ray Source,” presented at the 2011 Particle Accel.
Conf. (PAC’11), New York, U.S.A., March 28–April 1, 2011.
o
C. Rivetta et al., “Mathematical Models of Feedback Systems for Control of Intra-bunch
Instabilities driven by TMCI”, PAC2011
o
M. Pivi, C-MAD USER’S MANUAL, SLAC-PUB-14443
o
K. G. Sonnad, et al., “Simulations of Electron Cloud Induced Instabilities and Emittance
Growth for CESRTA”, PAC2011
o
M. Pivi, et al., “ILC Damping Ring Electron Cloud R&D Effort”, ECLOUD10 Workshop
o
M. Pivi,K. Sonnad, “Single-Bunch Instability Simulations in CESRTA”, ECLOUD10
Workshop
o
K. Sonnad, et al., “An Update on Simulation of Beam Dynamics with Electron Cloud
Effects”, ECLOUD10 Workshop
o
L. Wang, M. Pivi, “Trapping of Electron Cloud in ILC/CESRTA Quadrupole and Sextupole
Magnets”, ECLOUD10 Workshop
o
J. Calvi et al., “Electron Cloud Mitigation Investigations at CESR-TA”, ECLOUD10
Workshop
o
C. M. Spencer, et al., “A Project to Design and Build the Magnets for a New Test Beamline,
the ATF2, at KEK”, IEEE Trans.Appl.Supercond., SLAC-PUB-14339
o
Y. Sun, C. Adolphsen, “Linac alignment: 1-to-1 correction”, SLAC-PUB-14322
o
Y. Sun, C. Adolphsen, “Emittance growth in the NLCTA first chicane”, SLAC-PUB-14323
o
Y. Sun, C. Adolphsen, “A new linac steering algorithm”, SLAC-PUB-14466.
5. Accelerator Physics & Engineering Department
The mission of the Accelerator Physics & Engineering Department (APE) is to “Make Accelerators
Work”. APE works in the gap between what is traditionally considered physics and engineering for the
design and operation of existing and near term accelerator facilities. This includes accelerator design and
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Accelerator Research Division Quarterly Report – 2001/Q1
modeling, beam tuning and control, diagnostics, accelerator commissioning and operations. The
department core competency is generated by people who combine physics, engineering and accelerator
operations expertise.
APE supports a variety of accelerator projects with substantial efforts in:

ATF2: The ATF2 is a test facility designed to demonstrate the linear collider final focus optics
using the low emittance beam from the ATF damping ring at KEK in Japan
o
o
o
o

The ATF2 non-linear optical system requires the development of new tuning algorithms
which are tested on a simulator, then implemented on the accelerator. A new tuning algorithm
that does not require an operating spot size monitor was developed and tested in simulation
because the laser spot size monitor (developed by Tokyo University) has been unreliable in
recent runs.
The ATF2 uses 37 C-band cavity BPMs with electronics designed by SLAC, cavities
constructed by KEK and Pohang and algorithms and software developed at RHUL. The
cavity BPM system including the IP BPMs were commissioned this quarter.
Work at the ATF2 was halted by the disastrous March 11 earthquake which caused some
damage to ATF ring and ATF2. This quarter we expect to find out KEK’s plans for ATF2.
CLIC has become more heavily involved with ATF2 and is doing optics optimization using
MADX/MAPCLASS and investigating ultra-low beta* / ultra-high chromaticity optics, and
new final focus quads.
CTF3: The CTF3 facility at CERN is designed to demonstrate the high current drive beam
generation and two-beam acceleration required for the CLIC collider
o
o

The CLIC drive beam BPM design was completed and prototypes are being fabricated.
The CLIC main beam BPMs conceptual design is underway with possibilities of a common
design with LCLS_II and the Pohang XFEL.
o Studies of the transverse and longitudinal wakes of both main beam and drive beam BPMs
were done
o Conceptual design of readout electronics for CLIC beam instrumentation is underway.
o Calculation of beam impedances for damping ring, combiner ring, and drive beam turnaround
tapered stripline kickers is underway.
o Writing of Conceptual Design Report (CDR) sections on BPMs and beam instrumentation is
underway.
o An initial feasibility study is underway for a CLIC quadrupole stabilization demonstration
experiment at JLAB. The CLIC design requires main beam quadrupole magnetic field centers
to be stabilized to less than 2nm rms in a bandwidth 2 - 25 Hz. This is considered a
“feasibility issue” and performance should be demonstrated.
FACET: FACET is a SLAC project to use the front 2 km of the linac, damping rings and positron
system to generate high peak current test beams for plasma wakefield acceleration and other
experiments.
o
o
The preparation of the Sector 0-20 systems, damping rings and FACET experimental area is
continuing and is completed in time for the scheduled turn-on.
FACET feedbacks are under development and expected to be ready to start commissioning
for beam turn-on.
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Accelerator Research Division Quarterly Report – 2001/Q1
o
o
o

The Pyroelectric detectors for the FACET bunch length monitors have been fabricated and
the remainder of the system is expected to be completed next quarter.
The SAREC committee decided that the FACET THz source required more science
motivation. The THz power produced at FACET will be measured, but plans to transport the
THz to an experimental area are on hold.
Beamline models and MAD decks are being updated.
LCLS: The SLAC X-ray FEL system, now providing user beams.
o
o
o
o
o
o
o
o
o
o
o
o
Due to a calculation error, the X-ray beam divergence from the LCLS is 2x larger than
originally estimated and overfills the hard X-ray mirrors. A design was developed to install a
Be focusing lens in the X-ray diagnostics chamber (“ST0”). Unfortunately the commercial
UHV motion system was delivered very contaminated and could not be installed. We expect
to have parts from an alternate vendor installed next quarter.
The phase cavity timing noise problem that developed last quarter was tracked down to a
loose cable in a RF chasis and has been corrected. New phase cavity electronics designed to
operate at low charge have been installed and will be ready for operation at the end of the
down.
Short bunch (few-femtosecond) operation of the LCLS based on low charge (20-40pc) and
the slotted spoiler is regularly used by experimenters, however the existing diagnostics cannot
resolve bunches below 20 femtoseconds. A conceptual and optical design of a single shot
broad-band (6-50um) infra-red spectrometer for bunch length measurement was completed.
Fabrication of this system has been delayed by parts delivery times, but tests are expected to
begin next quarter.
The slotted-foil ultra-short X-ray pulse generation system is being upgraded with a new high
precision foil to allow shorter pulses and more flexibility.
The thermal-acoustic X-ray energy monitor has passed vacuum testing and will be ready for
beam operation after the down.
The LCLS THz source was used to demonstrate both linear and non-linear autocorrelation
scans.
A THz pump / X-ray probe test is being designed to be installed in the Undulator hall. This
will demonstrate the feasibility of this type of experiment before the THz line to the NEH is
constructed.
The Be solid attenuators are being replaced with diamond and Silicon to reduce beam
distortions. Some attenuators will be ready at beam turn-on, others are waiting for material
delivery.
The noise performance of the LCLS gas attenuator was found to be partially due to issues
with photomultiplier saturation and pulse timing changes with beam energy / gas pressure.
The PMTs are being replaced with high-signal tubes and the software is being modified to
allow gate timing and PMT high voltage to be automatically adjusted for different operating
conditions. A wiring problem on the gas detector solenoids was also found and corrected.
This work is expected to be completed next quarter.
The LCLS orbit response calculation is now able to fit BPM gain and roll angles of BPMs,
quadrupoles and corrector magnets. This will allow better characterization of the LCLS
optics.
A high resolution screen and optics were installed in PR18 in the A-line which allowed fewfemtosecond temporal resolution measurements.
A total of 4 thin Be foils have been damaged in the undulator / beam dump area. APE is
investigating alternatives to Be in these applications and has put a hold on installing more Be
foils in the vacuum chamber.
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Accelerator Research Division Quarterly Report – 2001/Q1
o
o

LCLS_II: The LCLS_II is a project to construct a new XFEL facility at SLAC to provide
additional capacity for more simultaneous user experiments.
o

The LCLS_II CDR was completed and presentations for the CD-1 review are being finalized.
LHC: Large Hadron Collider at CERN.
o
o
o

APE has been supporting the LINAC upgrade project to convert the RF system from SLC to
EPICS.
The fast feedback pulse by pulse control system is being used to develop semi-noninvasive
pulse-stealing diagnostics.
The LHC synchrotron light monitor is used to measure beam profiles and to detect particles
in the abort gap. Upgrades to the optical system were installed during the shutdown this
winter.
The forward proton detector system at LHC requires few-picosecond timing stability over
several hundred meters. Last quarter a copy of the coax distribution system developed for
LCLS demonstrated the required stability (scaled with cable length). Further development is
waiting for funding from LHC or LLNL.
In 2010 the DCCT used to measure average current in the LHC rings showed fill-pattern
sensitivity. The modifications implemented during the year-end shutdown, a repartioning of
gain and bandwidth profiles and an improvement of RF bypassing, appears to have solved
saturation problems. Beam tests this quarter have shown sufficient available headroom to
meet LHC needs until the 2013 shutdown. Additional benefits include improved signal
monitor bandwidth and improvement in matching of behavior of the devices in the
accelerator with the one in the lab. The LHC fast current transformer showed position
sensitivity, the cause of which has been identified, and a proposed solution is seen to work in
the lab, but has not yet been implemented
NLCTA: Test accelerator using X-band RF
o The operation of the NLCTA has been limited by the lack of automated tuning and feedback
systems which has made it difficult to reproduce beam conditions. Scripts and high level
applications from LCLS are being adapted for use at NCLTA. These include profile monitor
and emittance GUIs and the Schottky scan script.
o NLCTA / ECHO decks and models are being updated to include the new spectrometer and Xband TCAVs
6. Test Facilities
The mission of the Test Facilities Department (TFD) is to operate and support the test facilities at
SLAC that are utilized to develop and test near-term solutions for accelerator issues. RF
structures and power sources as well as beam optical, diagnostic and collimation systems are
tested in these facilities. The major test facilities are the Next Linear Collider Test Accelerator
(NLCTA), Accelerator Structure Test Area (ASTA), and L-band RF test facilities at End Station
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Accelerator Research Division Quarterly Report – 2001/Q1
B. TFD also supports the operation of FACET, End Station A (ESA), and the ATF/ATF2
program at KEK and works closely with the Klystron and the Power Conversion R&D groups.

ASTA report: The ASTA facility includes two s-band 50 MW klystrons who output can be
combined, a variable length pulse compressor with an output of up to 500 MW and an extremely
flexible RF system that is well suited for fast turnaround of experiments. The ASTA bunker’s
shielding is rated for up 100 MeV beam energies. At present is used extensively for testing of all
sorts of short RF structures and for testing materials that can be used in RF structure manufacture.
With a modest upgrade ASTA can be used to test RF guns. The past quarter activities in ASTA
were:
o
o
o
o
o

Operations for the High Gradient structure tests (see also AARD-Microwave report,
PETS2 and C10-VG0.7.5).
Planning for relocation of the cryogenic test stand into the ASTA vault.
Planning for upgrading facility for 24/7 and for remote operations from the NLCTA
control room. 24/7 operation requires design and installation of a fire-suppression system
for the modulators. Remote operations require upgrading the ASTA control system to
EPICS and upgrading the monitoring systems for remote readout and display. Parts for
the remote operation of ASTA have been purchased and are being installed. The fire
suppression system is under design review by SLAC.
A design for a spectrometer magnet can be use to characterize dark current coming out of
an RF gun.
Continuation as last quarter
NLCTA report: The NLCTA facility is housed in End Station B (ESB). At its heart is a former
320 MeV x-band linac (from the NLC project) with an s-band injector and an output beam line
and dump. The accelerator components are in their own enclosure inside the ESB hall. The past
quarter activities using NLCTA were:
o
o
Provide beam for E163 and the ECHO experiments (see also AARD-Laser for more
E163 information).
Provide a home for testing x-band RF. (see???)
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Accelerator Research Division Quarterly Report – 2001/Q1
o
o
o
o
o
Continued to rebuild the x-band two-pack for future use in the NLCTA accelerator as
power source for one transverse cavity, and long term testing of XL4 klystron tubes.
Continued upgrading the NLCTA beam line with addition of two transverse cavities for
increasing the beam energy spread and improved slice emittance measurement for the
ECHO-7 experiment.
Refurbished the dump spectrometer to a factor 3 better resolution.
Started to convert the NLCTA control system to EPICS, which will allow a more
homogeneous integration with higher level beam applications provided by the controls
department.
Continued the design of a new x-band test station in the beam dump area. This station
will have an x-band gun and some beam acceleration capability.

FACET User Area report: In anticipation of FACET construction completion (see status in ARD
Administration section), planning on the experimental user area and the purchase of a trailer for
FACET users is proceeding. Detailed installation planning for the user experiments has started.

End Station A: It is planned to have a new electron test beam in ESA (End Station Test Beam,
ESTB). Comissioning of the ESTB is expected in Winter of 2011. This test beam will provide the
full range of electron energies up to 13.6 GeV, and intensities from single particles to .25 nC/
bunch. It will be used primarily for detector R&D and machine developments. The designs for
kicker magnets and ceramic beam pipes to extract and transport beam from the LCLS linac to
ESA have been completed and are being fabricated. The implementation of the PPS system for
ESA has been started. A one day workshop on March 17, 2011 was met with overwhelming
response of 50 participants from 16 institutions. Eight test beam requests were submitted. The
first official user run is now scheduled for February 2012.

End Station B: In addition to housing the NLCTA, ESB also supports a range of high power RF
source development activities (in collaboration with the Accelerator Design Department and
others).
o MARX modulator testing. The failure of the MARX modulator capacitors under full load
has led to a study to measure capacitor aging. In the meanwhile the MARX modulator is
being run at reduced pulse width but with same power.
o The Cluster-Klystron concept prototype was installed on the NLCTA enclosure roof and
tested. Planning for a full scale test (160 meter big pipe) installed in the ESB has started.
o The two-pack system LLRF has been upgraded and modulator mods have been made to
facilitate design testing by AED’s Power Conversion Department. A fire suppression
system for the two-pack system has been installed.
o TTF3 coupler testing.
o

Continuation as last quarter
ECHO Experiment: Echo-7 is a proof-of-principle echo-enabled harmonic generation (EEHG)
experiment which is being performed at the NLCTA at SLAC. The experiment aims to test the
physics of the EEHG concept and demonstrate scaling. The 3rd, 4th, 5th, 7th, and possibly 15th
harmonic of a 1590nm seed laser will be generated through the EEHG scheme. In contrast to
other schemes for generating harmonic bunching (e.g. HGHG), higher harmonics can potentially
be reached with EEHG; in fact, due to the remarkable up-conversion efficiency, soft x-rays may
be reached directly from a UV seed laser.
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Accelerator Research Division Quarterly Report – 2001/Q1
o
o
o
After a successful summer 2010 run which provided a qualitative confirmation of the
ECHO theory, planning for an experiment aimed at making quantitative measurements by
summer of 2011 are underway
Continuation as last quarter
For technical improvements: see NLCTA
26