Contributions to ELI-NP on
RF accelerator activities
Andrea Mostacci
Università di Roma, Sapienza
The joint Sapienza/INFN-LNF group is active in the field of S-band, C-band, Xband accelerator devices design and construction. The group is interested
both in designing beam generation and manipulation devices as well as the
technological issues related to the construction of devices standing the high
RF power needed in modern accelerators. Through numerical simulation, we
study and optimize the electron beam dynamics in a single device as well as
in the whole machine. Moreover we are commissioning the LNF photoinjector (SPARC), the first S-band/C-band high brilliance linear accelerator.
As a university based group, we have also experience in training students in
their first steps in the accelerator physics and technology.
Goal
Show our experience and ongoing activities on RF issues of
accelerator physics which can be useful for ELI-NP
Group
L. Palumbo (Sapienza) and its group
M. Ferrario, B. Spataro, L. Serafini (INFN/LNF) and researchers
from INFN/LNF accelerator division
High brightness photo-injector (SPARC) commissioning.
R&D activities on RF issues
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
Outline
S-band devices: installation and operation of S-band
accelerator and in-house RF gun construction.
C-band devices: high gradient accelerating sections and RF
guns, installation and commissioning.
X-band devices: beam manipulation devices (e.g. harmonic
cavities) and beam generation devices (hybrid SW/TW gun).
Beam dynamics studies and optimisation (S-band, C-band,
X-band and mixed solutions).
Training and educational experience.
Contribution to ELI-NP.
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Commissioning of SPARC
High Brilliance photo-injector
Undulators
Diagnostic
and Matching
150 MeV
S-band linac
Contributions to ELI-NP on
RF accelerator activities
u = 2.8 cm
Velocity
Bunching
10 m
Kmax = 2.2
r = 500 nm
15 m
Long
Solenoids
S-band
Gun
Seeding
THz
Source
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
S-band devices (~ 3 GHz)
We presently are runnig a S-band linear accelerator producing high
brightness 180 MeV electorons.
We design, built and operate RF deflectors for beam length measurement.
Our device, first tested at SPARC, has been rebilt and installed in PSI
SWISS-FEL and FERMI FEL injectors.
A novel improved RF gun is at the executive design stage (design
scalable to higher frequencies).
SPARC RF Deflector
RF gun
Beam
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
C-band devices (~ 6 GHz)
For SPARC energy upgrade (180 250 MeV), we will install and operate inhouse built TW sections. (>35 MV/m accelerating field)
S-band injector in a C-band linac will be tested next year @ SPARC and it
is the solution adopted by SWISS-FEL @ PSI. After the succesful Spring 8
FEL, the C-band seems a mature and reliable technology.
For a given bunch charge, wake fields and beam loading are relaxed with
respect to higher frequency solutions. The same arguments holds for
timing, synchronization and jitters issues.
We are investigating a fully C-band linac design, including C-band RF gun.
Power test @ KEK
Symmetric input
coupler
Output
couplers
48 MV/m
Beam
RF power
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band devices: design & production
X-band (11.424 GHz) harmonic cavities for longitudinal phase space
compensation in high brilliance photo-injectors
Accelerating cells
RF CAD design
T
U
N
E
R
Beam
Coupling cells
RF power
Low power test and multi-cell cavity
tuning
Technological issues (high power
test @ SLAC), novel materials
1.5
1
Cu
0.5
0
HFSS
SuperFish
Mafia
Measur.
-0.5
-1
z axis
(cm)
Mo
-1.5
0
3
6
9
12
15
18
21
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
X-band devices: design & production
X-band (11.424 GHz) harmonic cavities for longitudinal phase space
compensation in high brilliance photo-injectors
Accelerating cells
RF power
9 cells
T
U
N
E
R
Contributions to ELI-NP on
RF accelerator activities
Beam
~ 17 cm
Low power test and multi-cell cavity
tuning
Coupling cells
Technological issues (high power
test @ SLAC), novel materials
1.5
1
Cu
0.5
0
HFSS
SuperFish
Mafia
Measur.
-0.5
-1
z axis
(cm)
Mo
-1.5
0
3
6
9
12
15
18
21
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band devices: R&D on manufacturing
We join the world wide effort to avoid hot brazing to
Photographs of three
manufactured X band
cavities:
(a) Cu brazed;
(b) Mo brazed;
(c) Cu electroformed.
V. Dolgachev, SLAC
B. Spataro, invited contribution to X-Band Structures, Beam Dynamics and Sources, December 2010
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band hybrid gun (Sapienza/INFN/UCLA)
SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the
power) to a lower gradient downstream TW section (no circulators needed).
The gun strongly longitudinally focuses, from velocity bunching due to 90°
phase shift between SW cell and input coupler.
EmittanceCompensating
Solenoids
Device under study
RF input
RF power
Photocathode
TW structure
(lower field)
RF Input
coupler
1.6 SW
structure
(higher field)
TW structure
2.5 SW structure
RF input
coupler
RF output
coupler
Next steps: RF design optimisation (with beam dynamics), hot tests …
The S-band version will be commissioned in 2011 @ UCLA (J. Rosenzweig)
The hybrid gun is part of the CRISP proposal.
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Beam dynamics studies
Simulations of particle beam evolution in linear and circular accelerators
based on macro-particle models.
Beam optimisation in S-band, C-band, X-band linac and for mixed
frequency machines (SPARC is the first linac operating at two frequencies)
Micro-bunching instability due to coherent synchrotron radiation (CSR) and
space charge in linear or in circular machines (e.g. RF and/or magnetic
compressors).
Beam dynamics optimization of accelerator devices (e.g. hybrid gun).
CSR in a ring
Bunch Length in hybrid gun
1OC temperature shift
energy
Contributions to ELI-NP on
RF accelerator activities
Study of collective effect due the particle wake fields.
time
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Beam dynamics studies for SPARX
SPARX is a mixed frequency machine (S-band/C-band) to be commissioned
before 2015 (C-band gun is under investigation).
C-band has been chosen for reliability consideration (as SWISS-FEL @ PSI).
SPARX has a nominal energy of 750 MeV (FEL operation) to 900 MeV (on
crest operation, corresponding to 18 MeV Compton photons).
Contributions to ELI-NP on
RF accelerator activities
Thermal emittance 0.6 um/mm, minimum emittance (Ferrario) working point.
Parmela/Astra simulation + scaling laws
Q
(pC)
ε
(μm)
Luminosity/spectral density
E peak
(MV/m)
Brightness
(A/m2)
Q/ε2
(pC/μm2)
S-band
1000
1.0
120
1.9 1014 (90 A)
1000
S-band
500
0.54
120
1.5 1014 (70 A)
1720
S-band
100
0.19
240
0.9 1014 (40 A)
2770
C-band
500
0.49
240
7.7 1014 (92 A)
2080
C-band (scaled)
250
0.37
240
6.1 1014 (73 A)
1830
X-band
250
0.27
480
2.5 1015 (90 A)
3400
X-band
250
0.28
350
1.5 1015 (58 A)
3400
X-band (Hyb. gun)
6.7
0.08
200
2.8 1016 (90 A)
1050
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
Educational and training experience
All the previous activities are pursued with the aid of students, either
master thesis or PhD level, that every year get their diploma at Sapienza
(Faculty of Engineering).
At the moment we have PhD and master students working on accelerator
physics topics.
The core topics where most of the students have been trained range from
beam dynamics in linear and circular machines (including collective
effects) to design methodology and bench measurements of RF devices
in particle accelerators at frequencies from S-band (3 GHz) to X-band (12
GHz).
In the framework of our long standing collaboration with INFN/LNF
accelerator physics division, we can also profit of the experience gained
at SPARC (an accelerator physics research machine) where many
talented PhD students from our university have been trained.
We give lectures in international accelerator schools, such as Joint
Universities Accelerator School (JUAS) or Cern Accelerator School (CAS).
We give also a course on Physics and Technology of Accelerators at the
University of Rome, Faculty of Engineering and Faculty of Physics.
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
Conclusions
We design and construct RF
devices for beam generation
(photo-gun) and beam manipulation
(IV harm. cavity, RF deflectors, …)
in the 3-12 GHz frequency range.
We have experience in beam
dynamics optimisation of
linear/circular machines
We take part to commissioning of
High Brilliance photo-injector
SPARC
We train PhDs and technical
engineers in accelerator physics
We are interested in
sharing our experience in
design and the realization
of RF devices for the ELINP accelerator
We are interested in
contributing to beam
dynamics studies and
commissioning of the
accelerator in ELI-NP
We are interested in
contributing to the setting
up of accelerator physics
expertise in ELI-NP
Ongoing collaborations:
INFN (other labs/sections), UCLA, CERN, LULI, ELI, EuroFEL (IRUVX FEL),
SLAC, KEK
Andrea.Mostacci@uniroma1.it
Contributions to ELI-NP on
RF accelerator activities
Additional
material
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band hybrid gun (Sapienza/INFN/UCLA)
SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the
power) to a lower gradient downstream TW section (no circulators needed).
The gun strongly longitudinally focuses, from velocity bunching due to 90°
phase shift between SW cell and input coupler.
EmittanceCompensating
Solenoids
Device under study
RF input
RF power
Photocathode
TW structure
(lower field)
RF Input
coupler
1.6 SW
structure
(higher field)
TW structure
2.5 SW structure
RF input
coupler
RF output
coupler
Next steps: RF design optimisation (with beam dynamics), hot tests …
The S-band version will be commissioned in 2011 @ UCLA (J. Rosenzweig)
The hybrid gun is part of the CRISP proposal.
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band hybrid gun (Sapienza/INFN/UCLA)
SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the
power) to a lower gradient downstream TW section (no circulators needed).
The gun strongly longitudinally focuses, from velocity bunching due to 90°
phase shift between SW cell and input coupler.
EmittanceCompensating
Solenoids
Device under study
RF input
RF input
coupler
Photocathode
TW structure
(lower field)
RF Input
coupler
1.6 SW
structure
(higher field)
2.5 SW structure
TW structure
Temperature sensitivity 200 kHz/oC
Next steps: RF design optimisation (with beam dynamics), hot tests …
The S-band version will be commissioned in 2011 @ UCLA
The hybrid gun is part of the CRISP proposal.
Andrea.Mostacci@uniroma1.it
ELI-NP: the way ahead
Bucharest, 10-12 March 2011
Contributions to ELI-NP on
RF accelerator activities
X-band hybrid gun (Sapienza/INFN/UCLA)
SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the
power) to a lower gradient downstream TW section (no circulators needed).
The gun strongly longitudinally focuses, from velocity bunching due to 90°
phase shift between SW cell and input coupler.
EmittanceCompensating
Solenoids
Device under study
RF input
@z=30cm σz< 10 mm (90 A)
εn,x< 0.08 mm-mrad
Photocathode
TW structure
(lower field)
RF Input
coupler
1.6 SW
structure
(higher field)
σx< 80 mm
Brilliance=2.8 1016 A/m2
6.7 pC
Solenoid @ 6 kG
Next steps: RF design optimisation (with beam dynamics), hot tests …
The S-band version will be commissioned in 2011 @ UCLA
The hybrid gun is part of the CRISP proposal.
Andrea.Mostacci@uniroma1.it