LINAC2012 - List of Keywords (FEL)

Paper	Title	Other Keywords	Page
SUPB006	Study of Beam-Based Alignment for Shanghai Soft X-Ray FEL Facility	linac, simulation, emittance, alignment	10
	D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao SINAP, Shanghai, People's Republic of China
	In linear accelerators, dispersion caused by quadrupole misalignment and transverse wake-field effect caused by alignment errors of accelerate structures will lead to a significant emittance growth. There are more stringent restrictions on SXFEL, the traditional optical alignment can no longer meet its requirements, but the Beam-Based Alignment(BBA) method allows more precise alignment, further reduce the Linac errors to meet SXFEL requirements .In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position ,but also the errors of undulator magnetic. In order to achieve alignment accuracy over longer distance, we measuring BPM data under different conditions and using SVD algorithm for calculation and analysis, we can get the quadrupole magnet errors and BPM offset. With the method above, software based on MATLAB has been designed and compared the results with other software.

MOPLB09	Status of the C-Band RF System for the SPARC-LAB High Brightness Photoinjector	klystron, coupling, electron, controls	162
	R. Boni, D. Alesini, M. Bellaveglia, G. Di Pirro, M. Ferrario, A. Gallo, B. Spataro INFN/LNF, Frascati (Roma), Italy A. Mostacci, L. Palumbo URLS, Rome, Italy
	The high brightness photoinjector in operation at the SPARC-LAB facility of the INFN-LNF, Italy, consists of a 150 MeV S-band electron accelerator aiming to explore the physics of low emittance high peak current electron beams and the related technology. Velocity bunching techniques, SASE and Seeded FEL experiments have been carried out successfully. To increase the beam energy and improve the performances of the experiments, it was decided to replace one S-band travelling wave accelerating cavity, with two C-band cavities that allow to reach higher energy gain per meter. The new C-band system is in a well advanced development phase and will be in operation early in 2013. The main technical issues of the C-band system and the R&D activities carried out till now are illustrated in detail in this paper.
	Slides MOPLB09 [1.061 MB]

MOPB007	Study of Microbunching Instabilitity in the Linac of the Shanghai Soft X-Ray Free Electron Laser Facility	linac, impedance, simulation, electron	189
	D. Huang, Q. Gu, M. Zhang SINAP, Shanghai, People's Republic of China
	The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Shanghai soft X-ray FEL project (SXFEL), which is planned to start construction by the end of 2012, will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the physical design of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is critical to the success of the project. Moreover, the contribution of the possible plasma effects to the instability will also be studied by modifying the physical model of the longitudinal space charge (LSC) impedance.

MOPB080	Status of the C-Band RF System for the SPARC-LAB High Brightness Photoinjector	klystron, coupling, electron, controls	360
	R. Boni, D. Alesini, M. Bellaveglia, G. Di Pirro, M. Ferrario, A. Gallo, B. Spataro INFN/LNF, Frascati (Roma), Italy A. Mostacci, L. Palumbo URLS, Rome, Italy
	The high brightness photoinjector in operation at the SPARC-LAB facility of the INFN-LNF, Italy, consists of a 150 MeV S-band electron accelerator aiming to explore the physics of low emittance high peak current electron beams and the related technology. Velocity bunching techniques, SASE and Seeded FEL experiments have been carried out successfully. To increase the beam energy and improve the performances of the experiments, it was decided to replace one S-band travelling wave accelerating cavity, with two C-band cavities that allow to reach higher energy gain per meter. The new C-band system is in a well advanced development phase and will be in operation early in 2013. The main technical issues of the C-band system and the R&D activities carried out till now are illustrated in detail in this paper.

MOPB083	Operational experience with the FERMI@Elettra S-band RF System	klystron, linac, gun, LLRF	369
	A. Fabris, P. Delgiusto, F. Gelmetti, M.M. Milloch, A. Milocco, F. Pribaz, C. Serpico, N. Sodomaco, R. Umer, L. Veljak ELETTRA, Basovizza, Italy
	FERMI@Elettra is a single-pass linac-based FEL user-facility covering the wavelength range from 100 nm (12 eV) to 4 nm (310 eV) and is located next to the third generation synchrotron radiation facility Elettra in Trieste, Italy. The machine is presently under commissioning and the first FEL line (FEL-1) will be opened to the users by the end of 2012. The 1.5 GeV linac is based on S-band technology. The S-band system is composed of fifteen 3 GHz 45 MW peak RF power plants powering the gun, eighteen accelerating structures and the RF deflectors. The S-band system has been set into operation in different phases starting from the second half of 2009. This paper provides an overview of the performance of the system, discussing the achieved results, the strategies adopted to assure them and possible upgrade paths to increase the operability and safety margins of the system.

TU2A03	LCLS Operation Experience and LCLS-II Design	undulator, electron, linac, photon	432
	T.O. Raubenheimer SLAC, Menlo Park, California, USA
	This talk will report the operations experience at LCLS and will describe the LCLS-II, a new X-ray FEL facility that uses the middle 1/3 of the SLAC linac as compared to the LCLS which uses the last 1/3 of the SLAC linac.
	Slides TU2A03 [4.761 MB]

TUPLB10	Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL	laser, electron, feedback, optics	467
	H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Togashi JASRI/SPring-8, Hyogo, Japan T. Matsukawa, H. Minamide RIKEN ASI, Sendai, Miyagi, Japan E. Takahashi RIKEN, Saitama, Japan
	Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.
	Slides TUPLB10 [2.713 MB]

TUPB006	Stability Performance of the Injector for SACLA/XFEL at SPring-8	laser, controls, undulator, cavity	486
	T. Asaka, T. Hasegawa, T. Inagaki, H. Maesaka, T. Ohshima, Y. Otake, S. Takahashi, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	To realize the SACLA, it is necessary to obtain stabilities of 10^-4 and 50 fs in the amplitude and time of an acceleration voltage, respectively. The achievement of the rf stabilities were almost satisfactory for the target values. Consequently, the 7 GeV beam energy stability was 0.02% (std.) or less. However, there was XFEL power variation caused by a variation of a beam position in a 40 MeV injector section. A periodically changed beam position of 40 μm (std.) was found out at a cycle of 2 s by Fourier transform method using BPM data. The temperatures of all the injector rf cavities are controlled within 28±0.04˚C by a controller using the cooling water. The AC power supplies of the controller to heat the cooling water are operated at 0.5 Hz by pulse width modulation control with alternatively turning on or off. The strong correlation between laser intensity variation and the modulation frequency of the AC power supplies was found out. We are planning to improve the cavity temperature variation in the order of less than 0.01˚C with DC power supplies to establish continuously regulated the cavity temperature. This plan will reduce the XFEL power variation.

TUPB008	Major Trends in Linac Design for X-ray FELs	electron, linac, cathode, emittance	489
	A. Zholents ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357. Major trends in the contemporary linac designs for x-ray free-electron lasers (XFELs) are outlined starting with identification of the key performance parameters, continuing with considerations of the design options for the electron gun and linac, and finishing with electron beam manipulation in the phase space.

TUPB009	C-Band Accelerating Structure Development and Tests for the SwissFEL	impedance, controls, klystron, linac	492
	R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin PSI, Villigen, Switzerland
	SwissFEL requires a 5.8 GeV beam provided by a C-band linac consisting of 104 two-meter accelerating structures. Each structure is of the constant gradient type and is composed of 113 cups. The cup shape is double-rounded to increase the quality factor. No tuning feature is implemented. For this reason ultra-precise turning is exploited. A strong R&D program has been launched on structure fabrication, which will be followed by a future technology transfer to a commercial company. The program includes the production and test of short structures that can be brazed in the existing PSI vacuum oven and will be completed with the production of the full two-meter prototype once the new full scale brazing oven, presently under construction, is operational. The status of the R&D program, including the production and power test results of the first two test structures, is reported here.

TUPB011	The Swiss FEL S-Band Accelerating Structure: RF Design	accelerating-gradient, linac, gun, impedance	498
	J.-Y. Raguin PSI, Villigen, Switzerland
	The Swiss FEL accelerator concept consists of a 450 MeV S-band injector Linac at 2998.8 GHz followed by the main linac at the C-band frequency aiming at a final energy of 5.8 GeV. The injector has six four-meter long S-band accelerating structures that shall operate with gradients up to 20 MV/m and with a 100 Hz repetition rate. Each structure has 122 cells, including the two coupler cells and operates with a 2π/3 phase advance. The design presented is such that the average dissipated RF power is constant over the whole length of the structure. The cells consist of cups and the cell irises have an elliptical profile to minimize the peak surface electric field. The coupler cells are of the double-feed type with a racetrack cross-section to cancel the dipolar components of the fields and to minimize its quadrupolar components.

TUPB012	The Swiss FEL C-Band Accelerating Structure: RF Design and Thermal Analysis	accelerating-gradient, linac, klystron, impedance	501
	J.-Y. Raguin, M. Bopp PSI, Villigen, Switzerland
	The Swiss FEL accelerator concept consists of a 450 MeV S-band injector linac followed by the main linac in C-band aiming at a final energy of 5.8 GeV. The two-meter long C-band accelerating structures have 113 cells, including the two coupler cells, and operate with a 2π/3 phase advance. The structure is of the constant-gradient type with rounded wall cells and has an average iris radius of 6.44 mm, a radius compatible with the impact of the short-range wakefields on the whole linac beam dynamics. The cell irises have an elliptical profile to minimize the peak surface electric fields and the coupler cells are of the J-type. We report here on the RF design of the structure, as well as on its thermal analysis, to target operational conditions with an accelerating gradient of about 28 MV/m and a repetition rate of 100 Hz.

TUPB014	Comparative Design of Single Pass, Photo-cathode RF-LINAC FEL for the THz Frequency Range: Self Amplification vs. Enhanced Super-radiance	radiation, electron, linac, wiggler	507
	Yu. Lurie, Y. Pinhasi Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
	Self amplified spontaneous emission and enhanced super-radiance are discussed and compared as possible configurations in the construction of a single-pass, photo-cathode RF-LINAC FEL source for THz radiation, being developed in Ariel University Center of Samaria. Numerical simulations carried out using 3D, space-frequency approach demonstrate the charge squared dependence of the radiation power in both cases, the characteristic typical to super-radiant emission. The comparison reveals a high efficiency of an enhanced super-radiance FEL, which however can only be achieved with ultra-short (the radiation wavelength long or shorter) drive electron beam bunches at a proper energy chirping.

TUPB018	Study of Beam-Based Alignment for Shanghai Soft X-Ray FEL Facility	linac, simulation, emittance, alignment	513
	D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao SINAP, Shanghai, People's Republic of China
	In linear accelerators, dispersion caused by quadrupole misalignment and transverse wake-field effect caused by alignment errors of accelerate structures will lead to a significant emittance growth. There are more stringent restrictions on SXFEL, the traditional optical alignment can no longer meet its requirements, but the Beam-Based Alignment(BBA) method allows more precise alignment, further reduce the Linac errors to meet SXFEL requirements .In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position ,but also the errors of undulator magnetic. In order to achieve alignment accuracy over longer distance, we measuring BPM data under different conditions and using SVD algorithm for calculation and analysis, we can get the quadrupole magnet errors and BPM offset. With the method above, software based on MATLAB has been designed and compared the results with other software.

TUPB022	A Passive Linearizer for Bunch Compression	electron, linac, laser, emittance	525
	Q. Gu, M. Zhang, M.H. Zhao SINAP, Shanghai, People's Republic of China
	In high gain free electron laser (FEL) facility design and operation, a high bunch current is required to get lasing with a reasonable gain length. Because of the current limitation of the electron source due to the space charge effect, a compression system is commonly used to compress the electron beam to the exact current needed. Before the bunch compression, the nonlinear energy spread due to the finite bunch length should be compensated; otherwise the longitudinal profile of bunch will be badly distorted. Usually an X band accelerating structure is used to compensate the nonlinear energy spread while decelerating the beam. For UV FEL facility, the X band system is too expensive comparing to the whole facility. In this paper, we present a corrugated structure as a passive linearizer, and the preliminary study of the beam dynamics is also shown.

TUPB080	Non-destructive Real-time Monitor to Measure 3D Bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-Seeded EUV-FEL	laser, electron, feedback, optics	657
	H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Togashi JASRI/SPring-8, Hyogo, Japan T. Matsukawa, H. Minamide RIKEN ASI, Sendai, Miyagi, Japan E. Takahashi RIKEN, Saitama, Japan
	Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3D overlapping electron bunches and higher harmonic generation (HH) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

WE1A03	Application of X-band Linacs	linac, emittance, gun, collider	724
	G. D'Auria ELETTRA, Basovizza, Italy
	Since the late 80’s the development of Normal Conducting (NC) X-band technology for particle accelerators has made significant progress and has witnessed tremendous growth. The driving force behind this technological development has been, and is, the interest of the scientific community in the construction of a Multi-TeV e⁺e⁻ Linear Collider at a reasonable size and cost. The use of the X-band frequency allows for a much higher accelerating gradient per meter, when compared to the S and C bands. SLAC, with a major contribution from KEK, has been pioneering this development since the late 80’s in the framework of the NLC/JLC projects. Later, in 2007, the same technology was chosen by CERN for CLIC, the 12 GHz Linear Collider based on the Two-Beam Acceleration (TBA) concept. In addition to these applications, X-band technology is also rapidly expanding in the field of X-ray FELs and other photon sources where it shows great potential. Here, a selection of X-band projects as well as the main applications of this technology at different international laboratories, is reported. The paper also includes a brief report on X-band medical and industrial applications.
	Slides WE1A03 [5.826 MB]

THPB089	Magnetic Characterization of the Phase Shifter Prototypes Built by CIEMAT for E-XFEL	undulator, electron, free-electron-laser, laser	1029
	I. Moya, J. Calero, J.M. Cela-Ruiz, L. García-Tabarés, A. Guirao, J.L. Gutiérrez, L.M. Martinez, T. Martínez de Alvaro, E. Molina Marinas, L. Sanchez, S. Sanz, F. Toral, C. Vázquez, J.G.S. de la Gama CIEMAT, Madrid, Spain J. Campmany, J. Marcos, V. Massana CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
	Funding: Work partially supported by Spanish Ministry of Science and Innovation under SEI Resolution on 17-September-2009 and project ref. AIC-2010-A-000524 The European X-ray Free Electron Laser (E-XFEL) will be based on a 10 to 17.5 GeV electron linac that will be used in the undulator system to obtain ultra-brilliant X-ray flashes from 0.1 to 6 nanometres for experimentation. The undulator system is formed by undulators and intersections between them, where a quadrupole on top of a precision mover, a beam position monitor, two air coils and a phase shifter are allocated. The function of the phase shifter is to adjust the phase of the electron beam and the radiation when they enter in an undulator according to the different beam energies and wavelengths. CIEMAT is working on the development of the phase shifters, as part of the Spanish in-kind contribution to the E-XFEL project. Several problems reported elsewhere were detected in the first prototype, which did not fulfil the first field integral specification. This paper describes the magnetic measurements realized on the second and third prototypes in the test bench at CELLS, together with the tuning process to decrease the field integral dependence with gap.

Paper

Title

Other Keywords

Page

SUPB006

Study of Beam-Based Alignment for Shanghai Soft X-Ray FEL Facility

linac, simulation, emittance, alignment

10

D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao
SINAP, Shanghai, People's Republic of China

In linear accelerators, dispersion caused by quadrupole misalignment and transverse wake-field effect caused by alignment errors of accelerate structures will lead to a significant emittance growth. There are more stringent restrictions on SXFEL, the traditional optical alignment can no longer meet its requirements, but the Beam-Based Alignment(BBA) method allows more precise alignment, further reduce the Linac errors to meet SXFEL requirements .In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position ,but also the errors of undulator magnetic. In order to achieve alignment accuracy over longer distance, we measuring BPM data under different conditions and using SVD algorithm for calculation and analysis, we can get the quadrupole magnet errors and BPM offset. With the method above, software based on MATLAB has been designed and compared the results with other software.

MOPLB09

Status of the C-Band RF System for the SPARC-LAB High Brightness Photoinjector

klystron, coupling, electron, controls

162

R. Boni, D. Alesini, M. Bellaveglia, G. Di Pirro, M. Ferrario, A. Gallo, B. Spataro
INFN/LNF, Frascati (Roma), Italy
A. Mostacci, L. Palumbo
URLS, Rome, Italy

The high brightness photoinjector in operation at the SPARC-LAB facility of the INFN-LNF, Italy, consists of a 150 MeV S-band electron accelerator aiming to explore the physics of low emittance high peak current electron beams and the related technology. Velocity bunching techniques, SASE and Seeded FEL experiments have been carried out successfully. To increase the beam energy and improve the performances of the experiments, it was decided to replace one S-band travelling wave accelerating cavity, with two C-band cavities that allow to reach higher energy gain per meter. The new C-band system is in a well advanced development phase and will be in operation early in 2013. The main technical issues of the C-band system and the R&D activities carried out till now are illustrated in detail in this paper.

Slides MOPLB09 [1.061 MB]

MOPB007

Study of Microbunching Instabilitity in the Linac of the Shanghai Soft X-Ray Free Electron Laser Facility

linac, impedance, simulation, electron

189

D. Huang, Q. Gu, M. Zhang
SINAP, Shanghai, People's Republic of China

The microbunching instability in the LINAC of a FEL facility has always been an issue which may degrade the quality of the electron beam. As the result, the whole facility may not be working properly. Shanghai soft X-ray FEL project (SXFEL), which is planned to start construction by the end of 2012, will be the first X-ray FEL facility in China. In this article, detailed study will be given based on the physical design of the facility to gain better understanding and control over the possible microbunching instability in SXFEL, which is critical to the success of the project. Moreover, the contribution of the possible plasma effects to the instability will also be studied by modifying the physical model of the longitudinal space charge (LSC) impedance.

MOPB080

Status of the C-Band RF System for the SPARC-LAB High Brightness Photoinjector

klystron, coupling, electron, controls

360

R. Boni, D. Alesini, M. Bellaveglia, G. Di Pirro, M. Ferrario, A. Gallo, B. Spataro
INFN/LNF, Frascati (Roma), Italy
A. Mostacci, L. Palumbo
URLS, Rome, Italy

The high brightness photoinjector in operation at the SPARC-LAB facility of the INFN-LNF, Italy, consists of a 150 MeV S-band electron accelerator aiming to explore the physics of low emittance high peak current electron beams and the related technology. Velocity bunching techniques, SASE and Seeded FEL experiments have been carried out successfully. To increase the beam energy and improve the performances of the experiments, it was decided to replace one S-band travelling wave accelerating cavity, with two C-band cavities that allow to reach higher energy gain per meter. The new C-band system is in a well advanced development phase and will be in operation early in 2013. The main technical issues of the C-band system and the R&D activities carried out till now are illustrated in detail in this paper.

MOPB083

Operational experience with the FERMI@Elettra S-band RF System

klystron, linac, gun, LLRF

369

A. Fabris, P. Delgiusto, F. Gelmetti, M.M. Milloch, A. Milocco, F. Pribaz, C. Serpico, N. Sodomaco, R. Umer, L. Veljak
ELETTRA, Basovizza, Italy

FERMI@Elettra is a single-pass linac-based FEL user-facility covering the wavelength range from 100 nm (12 eV) to 4 nm (310 eV) and is located next to the third generation synchrotron radiation facility Elettra in Trieste, Italy. The machine is presently under commissioning and the first FEL line (FEL-1) will be opened to the users by the end of 2012. The 1.5 GeV linac is based on S-band technology. The S-band system is composed of fifteen 3 GHz 45 MW peak RF power plants powering the gun, eighteen accelerating structures and the RF deflectors. The S-band system has been set into operation in different phases starting from the second half of 2009. This paper provides an overview of the performance of the system, discussing the achieved results, the strategies adopted to assure them and possible upgrade paths to increase the operability and safety margins of the system.

TU2A03

LCLS Operation Experience and LCLS-II Design

undulator, electron, linac, photon

432

T.O. Raubenheimer
SLAC, Menlo Park, California, USA

This talk will report the operations experience at LCLS and will describe the LCLS-II, a new X-ray FEL facility that uses the middle 1/3 of the SLAC linac as compared to the LCLS which uses the last 1/3 of the SLAC linac.

Slides TU2A03 [4.761 MB]

TUPLB10

Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL

laser, electron, feedback, optics

467

H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Togashi
JASRI/SPring-8, Hyogo, Japan
T. Matsukawa, H. Minamide
RIKEN ASI, Sendai, Miyagi, Japan
E. Takahashi
RIKEN, Saitama, Japan

Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

Slides TUPLB10 [2.713 MB]

TUPB006

Stability Performance of the Injector for SACLA/XFEL at SPring-8

laser, controls, undulator, cavity

486

T. Asaka, T. Hasegawa, T. Inagaki, H. Maesaka, T. Ohshima, Y. Otake, S. Takahashi, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

To realize the SACLA, it is necessary to obtain stabilities of 10^-4 and 50 fs in the amplitude and time of an acceleration voltage, respectively. The achievement of the rf stabilities were almost satisfactory for the target values. Consequently, the 7 GeV beam energy stability was 0.02% (std.) or less. However, there was XFEL power variation caused by a variation of a beam position in a 40 MeV injector section. A periodically changed beam position of 40 μm (std.) was found out at a cycle of 2 s by Fourier transform method using BPM data. The temperatures of all the injector rf cavities are controlled within 28±0.04˚C by a controller using the cooling water. The AC power supplies of the controller to heat the cooling water are operated at 0.5 Hz by pulse width modulation control with alternatively turning on or off. The strong correlation between laser intensity variation and the modulation frequency of the AC power supplies was found out. We are planning to improve the cavity temperature variation in the order of less than 0.01˚C with DC power supplies to establish continuously regulated the cavity temperature. This plan will reduce the XFEL power variation.

TUPB008

Major Trends in Linac Design for X-ray FELs

electron, linac, cathode, emittance

489

A. Zholents
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357.
Major trends in the contemporary linac designs for x-ray free-electron lasers (XFELs) are outlined starting with identification of the key performance parameters, continuing with considerations of the design options for the electron gun and linac, and finishing with electron beam manipulation in the phase space.

TUPB009

C-Band Accelerating Structure Development and Tests for the SwissFEL

impedance, controls, klystron, linac

492

R. Zennaro, J. Alex, H. Blumer, M. Bopp, A. Citterio, T. Kleeb, L. Paly, J.-Y. Raguin
PSI, Villigen, Switzerland

SwissFEL requires a 5.8 GeV beam provided by a C-band linac consisting of 104 two-meter accelerating structures. Each structure is of the constant gradient type and is composed of 113 cups. The cup shape is double-rounded to increase the quality factor. No tuning feature is implemented. For this reason ultra-precise turning is exploited. A strong R&D program has been launched on structure fabrication, which will be followed by a future technology transfer to a commercial company. The program includes the production and test of short structures that can be brazed in the existing PSI vacuum oven and will be completed with the production of the full two-meter prototype once the new full scale brazing oven, presently under construction, is operational. The status of the R&D program, including the production and power test results of the first two test structures, is reported here.

TUPB011

The Swiss FEL S-Band Accelerating Structure: RF Design

accelerating-gradient, linac, gun, impedance

498

J.-Y. Raguin
PSI, Villigen, Switzerland

The Swiss FEL accelerator concept consists of a 450 MeV S-band injector Linac at 2998.8 GHz followed by the main linac at the C-band frequency aiming at a final energy of 5.8 GeV. The injector has six four-meter long S-band accelerating structures that shall operate with gradients up to 20 MV/m and with a 100 Hz repetition rate. Each structure has 122 cells, including the two coupler cells and operates with a 2π/3 phase advance. The design presented is such that the average dissipated RF power is constant over the whole length of the structure. The cells consist of cups and the cell irises have an elliptical profile to minimize the peak surface electric field. The coupler cells are of the double-feed type with a racetrack cross-section to cancel the dipolar components of the fields and to minimize its quadrupolar components.

TUPB012

The Swiss FEL C-Band Accelerating Structure: RF Design and Thermal Analysis

accelerating-gradient, linac, klystron, impedance

501

J.-Y. Raguin, M. Bopp
PSI, Villigen, Switzerland

The Swiss FEL accelerator concept consists of a 450 MeV S-band injector linac followed by the main linac in C-band aiming at a final energy of 5.8 GeV. The two-meter long C-band accelerating structures have 113 cells, including the two coupler cells, and operate with a 2π/3 phase advance. The structure is of the constant-gradient type with rounded wall cells and has an average iris radius of 6.44 mm, a radius compatible with the impact of the short-range wakefields on the whole linac beam dynamics. The cell irises have an elliptical profile to minimize the peak surface electric fields and the coupler cells are of the J-type. We report here on the RF design of the structure, as well as on its thermal analysis, to target operational conditions with an accelerating gradient of about 28 MV/m and a repetition rate of 100 Hz.

TUPB014

Comparative Design of Single Pass, Photo-cathode RF-LINAC FEL for the THz Frequency Range: Self Amplification vs. Enhanced Super-radiance

radiation, electron, linac, wiggler

507

Yu. Lurie, Y. Pinhasi
Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel

Self amplified spontaneous emission and enhanced super-radiance are discussed and compared as possible configurations in the construction of a single-pass, photo-cathode RF-LINAC FEL source for THz radiation, being developed in Ariel University Center of Samaria. Numerical simulations carried out using 3D, space-frequency approach demonstrate the charge squared dependence of the radiation power in both cases, the characteristic typical to super-radiant emission. The comparison reveals a high efficiency of an enhanced super-radiance FEL, which however can only be achieved with ultra-short (the radiation wavelength long or shorter) drive electron beam bunches at a proper energy chirping.

TUPB018

Study of Beam-Based Alignment for Shanghai Soft X-Ray FEL Facility

linac, simulation, emittance, alignment

513

D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao
SINAP, Shanghai, People's Republic of China

In linear accelerators, dispersion caused by quadrupole misalignment and transverse wake-field effect caused by alignment errors of accelerate structures will lead to a significant emittance growth. There are more stringent restrictions on SXFEL, the traditional optical alignment can no longer meet its requirements, but the Beam-Based Alignment(BBA) method allows more precise alignment, further reduce the Linac errors to meet SXFEL requirements .In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position ,but also the errors of undulator magnetic. In order to achieve alignment accuracy over longer distance, we measuring BPM data under different conditions and using SVD algorithm for calculation and analysis, we can get the quadrupole magnet errors and BPM offset. With the method above, software based on MATLAB has been designed and compared the results with other software.

TUPB022

A Passive Linearizer for Bunch Compression

electron, linac, laser, emittance

525

Q. Gu, M. Zhang, M.H. Zhao
SINAP, Shanghai, People's Republic of China

In high gain free electron laser (FEL) facility design and operation, a high bunch current is required to get lasing with a reasonable gain length. Because of the current limitation of the electron source due to the space charge effect, a compression system is commonly used to compress the electron beam to the exact current needed. Before the bunch compression, the nonlinear energy spread due to the finite bunch length should be compensated; otherwise the longitudinal profile of bunch will be badly distorted. Usually an X band accelerating structure is used to compensate the nonlinear energy spread while decelerating the beam. For UV FEL facility, the X band system is too expensive comparing to the whole facility. In this paper, we present a corrugated structure as a passive linearizer, and the preliminary study of the beam dynamics is also shown.

TUPB080

Non-destructive Real-time Monitor to Measure 3D Bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-Seeded EUV-FEL

laser, electron, feedback, optics

657

H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Togashi
JASRI/SPring-8, Hyogo, Japan
T. Matsukawa, H. Minamide
RIKEN ASI, Sendai, Miyagi, Japan
E. Takahashi
RIKEN, Saitama, Japan

Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3D overlapping electron bunches and higher harmonic generation (HH) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

WE1A03

Application of X-band Linacs

linac, emittance, gun, collider

724

G. D'Auria
ELETTRA, Basovizza, Italy

Since the late 80’s the development of Normal Conducting (NC) X-band technology for particle accelerators has made significant progress and has witnessed tremendous growth. The driving force behind this technological development has been, and is, the interest of the scientific community in the construction of a Multi-TeV e⁺e⁻ Linear Collider at a reasonable size and cost. The use of the X-band frequency allows for a much higher accelerating gradient per meter, when compared to the S and C bands. SLAC, with a major contribution from KEK, has been pioneering this development since the late 80’s in the framework of the NLC/JLC projects. Later, in 2007, the same technology was chosen by CERN for CLIC, the 12 GHz Linear Collider based on the Two-Beam Acceleration (TBA) concept. In addition to these applications, X-band technology is also rapidly expanding in the field of X-ray FELs and other photon sources where it shows great potential. Here, a selection of X-band projects as well as the main applications of this technology at different international laboratories, is reported. The paper also includes a brief report on X-band medical and industrial applications.

Slides WE1A03 [5.826 MB]

THPB089

Magnetic Characterization of the Phase Shifter Prototypes Built by CIEMAT for E-XFEL

undulator, electron, free-electron-laser, laser

1029

I. Moya, J. Calero, J.M. Cela-Ruiz, L. García-Tabarés, A. Guirao, J.L. Gutiérrez, L.M. Martinez, T. Martínez de Alvaro, E. Molina Marinas, L. Sanchez, S. Sanz, F. Toral, C. Vázquez, J.G.S. de la Gama
CIEMAT, Madrid, Spain
J. Campmany, J. Marcos, V. Massana
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

Funding: Work partially supported by Spanish Ministry of Science and Innovation under SEI Resolution on 17-September-2009 and project ref. AIC-2010-A-000524
The European X-ray Free Electron Laser (E-XFEL) will be based on a 10 to 17.5 GeV electron linac that will be used in the undulator system to obtain ultra-brilliant X-ray flashes from 0.1 to 6 nanometres for experimentation. The undulator system is formed by undulators and intersections between them, where a quadrupole on top of a precision mover, a beam position monitor, two air coils and a phase shifter are allocated. The function of the phase shifter is to adjust the phase of the electron beam and the radiation when they enter in an undulator according to the different beam energies and wavelengths. CIEMAT is working on the development of the phase shifters, as part of the Spanish in-kind contribution to the E-XFEL project. Several problems reported elsewhere were detected in the first prototype, which did not fulfil the first field integral specification. This paper describes the magnetic measurements realized on the second and third prototypes in the test bench at CELLS, together with the tuning process to decrease the field integral dependence with gap.