FEL2013 - Table of Session: THOANO (Seeding & Harmonics)

Paper

Title

Page

Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator

728

H. Tomizawa, T. Hara, T. Ishikawa, K. Ogawa, H. Tanaka, T. Tanaka, T. Togashi, K. Togawa, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama, K. Yamakawa
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada, T. Sato, K. Yamanouchi
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Watanabe
JASRI/SPring-8, Hyogo, Japan
K. Midorikawa, E. Takahashi
RIKEN, Saitama, Japan

We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed.

Slides THOANO01 [11.493 MB]

THOANO02

Experimental Demonstration of Echo-enabled Harmonic Generation at the 14th Harmonic

D. Xiang, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, S.P. Weathersby
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. DOE under Contract No. DE-AC02-76SF00515.
Following the successful demonstration of echo-enabled harmonic generation [1] (EEHG [2]) with n=7 [3] at SLAC's NLCTA in 2011 [4], the beam line has been upgraded recently to benchmark EEHG theory at much higher harmonics. An optical parametric amplifier has been used to provide a seed with wavelength at 2.4 μm. Using an rf undulator as the radiator, coherent radiation at the 14th harmonic of the seed, i.e. with wavelength at 171 nm, has been generated using EEHG technique with a 120 MeV beam. We will present detailed experimental results on testing EEHG at n=14. Future plans in testing EEHG at n=30~75 in the coming year will be briefly discussed as well.
[1] G. Stupakov, PRL 102, 074801 (2009).
[2] D. Xiang and G. Stupakov, PRST-AB 12, 030702 (2009).
[3] D. Xiang et al., PRL 105, 114801 (2010).
[4] D. Xiang et al., PRL 108, 024802 (2012)

Slides THOANO02 [2.288 MB]

THOANO03

Experimental Characterization of the Laser Heater Effects on a Seeded FEL

E. Ferrari, E. Allaria, W.M. Fawley, L. Giannessi, G. Penco, S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
W.M. Fawley
LBNL, Berkeley, California, USA
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
Z. Huang
SLAC, Menlo Park, California, USA

High brightness electron beams necessary for high gain FEL usually require a laser heater in order to increase the local energy spread in the low energy part of the machine that can mitigate the microbunching instabilities developing in the compressors and in the rest of the linac. Microbunching suppression is essential for FEL operations both in SASE and in seeded mode since it can strongly affect the final electron beam properties. In the case of HGHG, due to the seeding mechanism, the FEL process is extremely sensitive to the amount of energy spread at the undulator entrance, and the FEL output may depend to the amount of heating. In this work we characterize the dependence of the FEL output as a function of the laser heater intensity in the case of FERMI FEL-1. Results also show that for a non Gaussian distribution of the electron beam energy the HGHG may produce significant radiation with an energy spread significantly higher than what expected for a simple Gaussian distribution.

Slides THOANO03 [2.333 MB]

THOANO04

Experimental Studies of Echo-enabled HG FEL

Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D. Xiang
SLAC, Menlo Park, California, USA

After echo-enabled HG FEL was studied theoretically and numerically, several experiments have been done to verify it. An overview of the experiments over the world and new understanding of it will be given in this talk.

Slides THOANO04 [18.207 MB]

Paper	Title	Page
THOANO01	Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator	728
	H. Tomizawa, T. Hara, T. Ishikawa, K. Ogawa, H. Tanaka, T. Tanaka, T. Togashi, K. Togawa, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama, K. Yamakawa JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada, T. Sato, K. Yamanouchi The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Watanabe JASRI/SPring-8, Hyogo, Japan K. Midorikawa, E. Takahashi RIKEN, Saitama, Japan
	We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed.
	Slides THOANO01 [11.493 MB]

THOANO02	Experimental Demonstration of Echo-enabled Harmonic Generation at the 14th Harmonic
	D. Xiang, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, S.P. Weathersby SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. DOE under Contract No. DE-AC02-76SF00515. Following the successful demonstration of echo-enabled harmonic generation [1] (EEHG [2]) with n=7 [3] at SLAC's NLCTA in 2011 [4], the beam line has been upgraded recently to benchmark EEHG theory at much higher harmonics. An optical parametric amplifier has been used to provide a seed with wavelength at 2.4 μm. Using an rf undulator as the radiator, coherent radiation at the 14th harmonic of the seed, i.e. with wavelength at 171 nm, has been generated using EEHG technique with a 120 MeV beam. We will present detailed experimental results on testing EEHG at n=14. Future plans in testing EEHG at n=30~75 in the coming year will be briefly discussed as well. [1] G. Stupakov, PRL 102, 074801 (2009). [2] D. Xiang and G. Stupakov, PRST-AB 12, 030702 (2009). [3] D. Xiang et al., PRL 105, 114801 (2010). [4] D. Xiang et al., PRL 108, 024802 (2012)
	Slides THOANO02 [2.288 MB]

THOANO03	Experimental Characterization of the Laser Heater Effects on a Seeded FEL
	E. Ferrari, E. Allaria, W.M. Fawley, L. Giannessi, G. Penco, S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy W.M. Fawley LBNL, Berkeley, California, USA L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy Z. Huang SLAC, Menlo Park, California, USA
	High brightness electron beams necessary for high gain FEL usually require a laser heater in order to increase the local energy spread in the low energy part of the machine that can mitigate the microbunching instabilities developing in the compressors and in the rest of the linac. Microbunching suppression is essential for FEL operations both in SASE and in seeded mode since it can strongly affect the final electron beam properties. In the case of HGHG, due to the seeding mechanism, the FEL process is extremely sensitive to the amount of energy spread at the undulator entrance, and the FEL output may depend to the amount of heating. In this work we characterize the dependence of the FEL output as a function of the laser heater intensity in the case of FERMI FEL-1. Results also show that for a non Gaussian distribution of the electron beam energy the HGHG may produce significant radiation with an energy spread significantly higher than what expected for a simple Gaussian distribution.
	Slides THOANO03 [2.333 MB]

THOANO04	Experimental Studies of Echo-enabled HG FEL
	Z.T. Zhao SINAP, Shanghai, People's Republic of China D. Xiang SLAC, Menlo Park, California, USA
	After echo-enabled HG FEL was studied theoretically and numerically, several experiments have been done to verify it. An overview of the experiments over the world and new understanding of it will be given in this talk.
	Slides THOANO04 [18.207 MB]