contributions to eli-np on rf accelerator activities andrea mostacci università di roma, sapienza...
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Contributions to ELI-NP on RF accelerator activities
Andrea MostacciUniversità di Roma, Sapienza
The joint Sapienza/INFN-LNF group is active in the field of S-band, C-band, X-band 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 photo-injector (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.
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OutlineGoal Show our experience and ongoing activities on RF issues of
accelerator physics which can be useful for ELI-NP
Group
M. Ferrario, B. Spataro, L. Serafini (INFN/LNF) and researchers from INFN/LNF accelerator division
R&
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X-band devices: beam manipulation devices (e.g. harmonic cavities) and beam generation devices (hybrid SW/TW gun).
C-band devices: high gradient accelerating sections and RF guns, installation and commissioning.
Beam dynamics studies and optimisation (S-band, C-band, X-band and mixed solutions).
High brightness photo-injector (SPARC) commissioning.
Training and educational experience.
Contribution to ELI-NP.
L. Palumbo (Sapienza) and its group
S-band devices: installation and operation of S-band accelerator and in-house RF gun construction.
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011 Commissioning of SPARC
S-band Gun
Velocity Bunching
Long Solenoids
Diagnostic and Matching
Seeding
THz Source
150 MeV
S-band linac
10 m
Undulators
u = 2.8 cm
Kmax = 2.2
r = 500 nm
15 m
High Brilliance photo-injector
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011 S-band devices (~ 3 GHz)
We presently are runnig a S-band linear accelerator producing high brightness 180 MeV electorons.
A novel improved RF gun is at the executive design stage (design scalable to higher frequencies).
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.
SPARC RF Deflector RF gun
Beam
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011 C-band devices (~ 6 GHz)
For SPARC energy upgrade (180 250 MeV), we will install and operate in-house built TW sections. (>35 MV/m accelerating field)
Symmetric inputcoupler
Outputcouplers
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.
We are investigating a fully C-band linac design, including C-band RF gun.
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.
Beam
RF power
48 MV/m
Power test @ KEK
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011 X-band devices: design & production
X-band (11.424 GHz) harmonic cavities for longitudinal phase space compensation in high brilliance photo-injectors
Technological issues (high power test @ SLAC), novel materials
Low power test and multi-cell cavity tuning
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Accelerating cells
TUNER
Coupling cells
Cu
Mo
RF power
Beam
RF CAD design
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011 X-band devices: design & production
Technological issues (high power test @ SLAC), novel materials
Low power test and multi-cell cavity tuning
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~ 17 cm
9 cells
Accelerating cells
TUNER
Coupling cells
Cu
Mo
RF power
Beam
X-band (11.424 GHz) harmonic cavities for longitudinal phase space compensation in high brilliance photo-injectors
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011 X-band devices: R&D on manufacturing
Photographs of three manufactured X band cavities: (a) Cu brazed; (b) Mo brazed;(c) Cu electroformed.
B. Spataro, invited contribution to X-Band Structures, Beam Dynamics and Sources, December 2010
V. Dolgachev, SLAC
We join the world wide effort to avoid hot brazing to
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011 X-band hybrid gun (Sapienza/INFN/UCLA)
The S-band version will be commissioned in 2011 @ UCLA (J. Rosenzweig)
Device under studyEmittance-CompensatingSolenoids
Photo-cathode
RF input
Laser(266 nm)
Electrons
RF Input couplerTW structure
(lower field)
1.6 SW structure(higher field)
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.
Next steps: RF design optimisation (with beam dynamics), hot tests …
The hybrid gun is part of the CRISP proposal.
2.5 SW structure TW structure
RF input coupler
RF output coupler
RF power
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011 Beam dynamics studies
Simulations of particle beam evolution in linear and circular accelerators based on macro-particle models.
Study of collective effect due the particle wake fields.
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).
Beam optimisation in S-band, C-band, X-band linac and for mixed frequency machines (SPARC is the first linac operating at two frequencies)
CSR in a ring Bunch Length in hybrid gun
time
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1OC temperature shift
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011 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).
SPARX has a nominal energy of 750 MeV (FEL operation) to 900 MeV (on crest operation, corresponding to 18 MeV Compton photons).
C-band has been chosen for reliability consideration (as SWISS-FEL @ PSI).
Thermal emittance 0.6 um/mm, minimum emittance (Ferrario) working point.
Q (pC)
ε (μm)
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
Luminosity/spectral densityParmela/Astra simulation + scaling laws
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011 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).
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.
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.
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).
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011 Conclusions
Ongoing collaborations:
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
INFN (other labs/sections), UCLA, CERN, LULI, ELI, EuroFEL (IRUVX FEL), SLAC, KEK
We are interested in sharing our experience in design and the realization of RF devices for the ELI-NP accelerator
We are interested in contributing to the setting up of accelerator physics expertise in ELI-NP
We are interested in contributing to beam dynamics studies and commissioning of the accelerator in ELI-NP
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Additional material
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The S-band version will be commissioned in 2011 @ UCLA (J. Rosenzweig)
Device under studyEmittance-CompensatingSolenoids
Photo-cathode
RF input
Laser
Electrons
RF Input couplerTW structure
(lower field)
1.6 SW structure(higher field)
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.
Next steps: RF design optimisation (with beam dynamics), hot tests …
The hybrid gun is part of the CRISP proposal.
2.5 SW structure TW structure
RF input coupler
RF output coupler
RF power
X-band hybrid gun (Sapienza/INFN/UCLA)
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The S-band version will be commissioned in 2011 @ UCLA
Device under studyEmittance-CompensatingSolenoids
Photo-cathode
RF input
Laser
Electrons
RF Input couplerTW structure
(lower field)
1.6 SW structure(higher field)
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.
Next steps: RF design optimisation (with beam dynamics), hot tests …
The hybrid gun is part of the CRISP proposal.
2.5 SW structure TW structure
RF input coupler
X-band hybrid gun (Sapienza/INFN/UCLA)
Temperature sensitivity 200 kHz/oC
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The S-band version will be commissioned in 2011 @ UCLA
Device under studyEmittance-CompensatingSolenoids
Photo-cathode
RF input
Laser
Electrons
RF Input couplerTW structure
(lower field)
1.6 SW structure(higher field)
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.
Next steps: RF design optimisation (with beam dynamics), hot tests …
The hybrid gun is part of the CRISP proposal.
@z=30cm σz< 10 m (90 A)εn,x< 0.08 mm-mrad
σx< 80 m
6.7 pC
Brilliance=2.8 1016 A/m2
X-band hybrid gun (Sapienza/INFN/UCLA)
Solenoid @ 6 kG