FEL2011 - List of Keywords (factory)

Paper	Title	Other Keywords	Page
MOPB19	Using Laser Harmonics to Increase Bunching Factor in EEHG	bunching, laser, undulator, FEL	45
	G.V. Stupakov SLAC, Menlo Park, California, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	Funding: This work was supported by U.S. DOE Contracts No. DE-AC02-76SF00515 and DE-AC02-05CH11231 Echo-enabled harmonic generation (EEHG) is one of most promising approaches to seeding of soft x-ray FELs. It allows one to obtain beam bunching at high harmonics (of order of 100) of the laser frequency at a level of a few percent. In this paper we demonstrate that using the second and third harmonics of the laser radiation one can substantially increase the beam bunching: for a cold beam one can obtain values approaching 0.4 in the range of harmonic numbers 100~200. Such bunching factors are close to those achieved at saturation in the FEL process, which means that one can eliminate the lasing process and use coherent radiation of the pre-bunched beam in the undulator-radiator as a bright source of x-rays. We also discuss an option of using nonlinear dispersive elements to increase the bunching factor.

WEPA16	Quasi-cw Normal Conducting Linac for Soft XFEL	linac, wakefield, klystron, dipole	359
	F. Wang, C. Adolphsen SLAC, Menlo Park, California, USA
	The CW operating soft XFELs have been proposed worldwide to serve large user community simultaneous. In principle, the superconducting linac technology is the only solution to realize such a cw light source. However, large amount of R&D efforts are still needed to build such a linac, which could delay such facility for a significant long period. Therefore, it will be very important to explore the other technology based such XFEL, like the normal conducting based quasi-cw (10s kHz) linac. With the initial study, it turns out that such a quasi-cw linac could be built with L-band (1.3 GHz) or X-band (11.4 GHz) technology. And the L-band devices for such a linac have been developed in the frame work of ILC.

THPA07	A Multichannel Wavelength Resolved Coherent Radiation Detector for Bunch Profile Monitoring at FLASH	radiation, electron, vacuum, FEL	477
	S. Wesch, B. Schmidt DESY, Hamburg, Germany
	Measuring the wavelength integrated intensity of coherent radiation in the micrometer to millimeter regime (THz radiation) is a widespread method to monitor the compression process in FEL linacs. While these devices give valuable information about the overall bunch length, they don't provide any information on the longitudinal structure and shape of the bunches. In this paper, we present a real time bunch profile monitor based on wavelength resolved THz detection. An in-vacuum spectrometer with four dispersive gratings and parallel read out of 120 individual wavelength bins provides detailed information shot-to-shot information on the bunch shape. The device can be operated in short (4-40 μm) and long range (40-400 μm) mode to cover the entire longitudinal phase space for compressed bunches of the FLASH linac. It is used as online monitoring device just as for bunch profile measurements during machine development. It's sensitivity down to the few micrometer scale allows to study very short features of the bunch profile as well as microbunching phenomena in this regime.

THPA29	Performance of the RF Cavity BPM at XFEL/SPring-8 “SACLA”	cavity, undulator, electron, low-level-rf	539
	H. Maesaka, T. Ohshima, Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H. Ego, S. Matsubara JASRI/SPring-8, Hyogo-ken, Japan S.I. Inoue SES, Hyogo-pref., Japan T. Shintake RIKEN Spring-8 Harima, Hyogo, Japan
	We have developed an rf cavity beam position monitor (RF-BPM) for the XFEL facility at SPring-8, “SACLA”. The demanded position resolution of the BPM is less than 1 μm, because an electron beam and X-rays must be overlapped with 4 μm precision in the undulator section. To achieve this requirement, we employed a C-band RF-BPM that has a resonant frequency of 4760 MHz. The RF-BPM has a TM110 dipole mode resonator for position detection and a TM010 monopole mode resonator for phase reference and charge normalization. Rf signals from the RF-BPM are detected by IQ (In-phase and Quadrature) demodulators and the detected signals are recorded by 238 MHz waveform digitizers. The position resolution was confirmed to be 0.2 μm by using a 250 MeV electron beam at the SCSS test accelerator. Then, 57 RF-BPMs were produced and installed into SACLA. The beam tuning of SACLA started in February 2011 and the RF-BPM system has been working well. We report the basic performance such as a resonant frequency, a Q factor, machining accuracy etc. for each cavity and the achieved position resolution of the RF-BPM system.

THPB28	The High Power Test Model of C-band Accelerating Structure for Compact XFEL at SINAP	impedance, linac, target, wakefield	617
	W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China D.C. Tong TUB, Beijing, People's Republic of China
	R&D of a C-band (5712 MHz) high gradient traveling-wave accelerating structure is being in progress at Shanghai Institute of Applied Physics (SINAP). Conceptual design of the accelerating structure has been accomplished, and verified by the cold test of the experimental model. Now the first prototype structure is ready for high RF power test and the optimization of a new operating mode is proposed for developing a robust high gradient C-band struture. In this paper, the results of the cold test of the first prototype structure and the optimization details are introduced.

Paper

Title

Other Keywords

Page

MOPB19

Using Laser Harmonics to Increase Bunching Factor in EEHG

bunching, laser, undulator, FEL

45

G.V. Stupakov
SLAC, Menlo Park, California, USA
M.S. Zolotorev
LBNL, Berkeley, California, USA

Funding: This work was supported by U.S. DOE Contracts No. DE-AC02-76SF00515 and DE-AC02-05CH11231
Echo-enabled harmonic generation (EEHG) is one of most promising approaches to seeding of soft x-ray FELs. It allows one to obtain beam bunching at high harmonics (of order of 100) of the laser frequency at a level of a few percent. In this paper we demonstrate that using the second and third harmonics of the laser radiation one can substantially increase the beam bunching: for a cold beam one can obtain values approaching 0.4 in the range of harmonic numbers 100~200. Such bunching factors are close to those achieved at saturation in the FEL process, which means that one can eliminate the lasing process and use coherent radiation of the pre-bunched beam in the undulator-radiator as a bright source of x-rays. We also discuss an option of using nonlinear dispersive elements to increase the bunching factor.

WEPA16

Quasi-cw Normal Conducting Linac for Soft XFEL

linac, wakefield, klystron, dipole

359

F. Wang, C. Adolphsen
SLAC, Menlo Park, California, USA

The CW operating soft XFELs have been proposed worldwide to serve large user community simultaneous. In principle, the superconducting linac technology is the only solution to realize such a cw light source. However, large amount of R&D efforts are still needed to build such a linac, which could delay such facility for a significant long period. Therefore, it will be very important to explore the other technology based such XFEL, like the normal conducting based quasi-cw (10s kHz) linac. With the initial study, it turns out that such a quasi-cw linac could be built with L-band (1.3 GHz) or X-band (11.4 GHz) technology. And the L-band devices for such a linac have been developed in the frame work of ILC.

THPA07

A Multichannel Wavelength Resolved Coherent Radiation Detector for Bunch Profile Monitoring at FLASH

radiation, electron, vacuum, FEL

477

S. Wesch, B. Schmidt
DESY, Hamburg, Germany

Measuring the wavelength integrated intensity of coherent radiation in the micrometer to millimeter regime (THz radiation) is a widespread method to monitor the compression process in FEL linacs. While these devices give valuable information about the overall bunch length, they don't provide any information on the longitudinal structure and shape of the bunches. In this paper, we present a real time bunch profile monitor based on wavelength resolved THz detection. An in-vacuum spectrometer with four dispersive gratings and parallel read out of 120 individual wavelength bins provides detailed information shot-to-shot information on the bunch shape. The device can be operated in short (4-40 μm) and long range (40-400 μm) mode to cover the entire longitudinal phase space for compressed bunches of the FLASH linac. It is used as online monitoring device just as for bunch profile measurements during machine development. It's sensitivity down to the few micrometer scale allows to study very short features of the bunch profile as well as microbunching phenomena in this regime.

THPA29

Performance of the RF Cavity BPM at XFEL/SPring-8 “SACLA”

cavity, undulator, electron, low-level-rf

539

H. Maesaka, T. Ohshima, Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Ego, S. Matsubara
JASRI/SPring-8, Hyogo-ken, Japan
S.I. Inoue
SES, Hyogo-pref., Japan
T. Shintake
RIKEN Spring-8 Harima, Hyogo, Japan

We have developed an rf cavity beam position monitor (RF-BPM) for the XFEL facility at SPring-8, “SACLA”. The demanded position resolution of the BPM is less than 1 μm, because an electron beam and X-rays must be overlapped with 4 μm precision in the undulator section. To achieve this requirement, we employed a C-band RF-BPM that has a resonant frequency of 4760 MHz. The RF-BPM has a TM110 dipole mode resonator for position detection and a TM010 monopole mode resonator for phase reference and charge normalization. Rf signals from the RF-BPM are detected by IQ (In-phase and Quadrature) demodulators and the detected signals are recorded by 238 MHz waveform digitizers. The position resolution was confirmed to be 0.2 μm by using a 250 MeV electron beam at the SCSS test accelerator. Then, 57 RF-BPMs were produced and installed into SACLA. The beam tuning of SACLA started in February 2011 and the RF-BPM system has been working well. We report the basic performance such as a resonant frequency, a Q factor, machining accuracy etc. for each cavity and the achieved position resolution of the RF-BPM system.

THPB28

The High Power Test Model of C-band Accelerating Structure for Compact XFEL at SINAP

impedance, linac, target, wakefield

617

W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

R&D of a C-band (5712 MHz) high gradient traveling-wave accelerating structure is being in progress at Shanghai Institute of Applied Physics (SINAP). Conceptual design of the accelerating structure has been accomplished, and verified by the cold test of the experimental model. Now the first prototype structure is ready for high RF power test and the optimization of a new operating mode is proposed for developing a robust high gradient C-band struture. In this paper, the results of the cold test of the first prototype structure and the optimization details are introduced.