FEL2012 - List of Authors (Ratner, D.F.)

Paper

Title

Page

Laser Phase Errors in Seeded FELs

17

D.F. Ratner, A.R. Fry, G.V. Stupakov, W.E. White
SLAC, Menlo Park, California, USA

Harmonic seeding is a promising method for producing transform-limited FEL pulses in the soft x-ray region. While harmonic multiplication schemes extend seeding to shorter wavelengths, they also amplify the spectral phase errors of the initial seed laser, degrading the final pulse quality and decreasing longitudinal coherence. Here we consider the effect of seed laser phase errors on longitudinal coherence for high gain harmonic generation and echo-enabled harmonic generation. We develop simulations to confirm analytical results for the case of linearly chirped seed lasers, and extend the results for arbitrary seed laser envelope and phase.

Slides MOOCI01 [2.534 MB]

TUOAI02

Hard X-ray Self-Seeding at the LCLS

R.R. Lindberg, W. Berg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents
ANL, Argonne, USA
J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, D.R. Walz, J.J. Welch, J. Wu, D. Zhu
SLAC, Menlo Park, California, USA
V.D. Blank, S. Terentiev
TISNCM, Troitsk, Russia
P. Emma
LBNL, Berkeley, California, USA
S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The Linac Coherent Light Source (LCLS) has produced extremely bright hard x-ray pulses using self-amplified spontaneous emission (SASE) since 2009. In SASE, the electron beam shot noise initiates the FEL gain, resulting in output radiation characterized by poor temporal coherence and a fluctuating spectrum whose normalized width is given by the FEL bandwidth. Recently, colleagues at DESY suggested a self-seeding scheme for the LCLS to reduce the bandwidth*. Here, the SASE produced in the first half of the undulator line is put through a simple diamond-based monochromator; the resulting monochromatic light trailing the main SASE pulse is used to seed the FEL interaction in the downstream undulators. We report on the experimental results implementing such a scheme at the LCLS, in which we have measured a reduction in bandwidth by a factor of 40-50 from that of SASE at 8-9 keV. The self-seeded FEL operates close to saturation, with the maximum output energy approximately equal to that with no seeding for low charge. The observed level of power fluctuations in the seeded output is presently rather large, and future plans focus on discovering their origins and reducing their magnitude.
* Geloni, V. Kocharyan ,and E.L. Saldin, DESY 10-133, arXiv:10⁰⁸.3036 (2010)

Slides TUOAI02 [22.104 MB]

THPD50

Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-based Light Sources

646

D.F. Ratner, A. Chao
SLAC, Menlo Park, California, USA
Y. Jiao
IHEP, Beijing, People's Republic of China

Modern accelerator light sources are based on either linac-FELs or storage rings. The linac-FEL type has high brilliance (microbunched beam) but low repetition rate. The storage ring type has high repetition rate (rapid beam circulation) but low brilliance. We propose to explore the feasibility of a microbunched beam in a storage ring that promises high repetition rate and high brilliance. The steady-state microbunched (SSMB) beam in a storage ring could provide CW sources for THz, EUV, or soft X-rays. We review several recently proposed SSMB concepts as promising directions for high brightness, high repetition rate light sources of the future.

Paper	Title	Page
MOOCI01	Laser Phase Errors in Seeded FELs	17
	D.F. Ratner, A.R. Fry, G.V. Stupakov, W.E. White SLAC, Menlo Park, California, USA
	Harmonic seeding is a promising method for producing transform-limited FEL pulses in the soft x-ray region. While harmonic multiplication schemes extend seeding to shorter wavelengths, they also amplify the spectral phase errors of the initial seed laser, degrading the final pulse quality and decreasing longitudinal coherence. Here we consider the effect of seed laser phase errors on longitudinal coherence for high gain harmonic generation and echo-enabled harmonic generation. We develop simulations to confirm analytical results for the case of linearly chirped seed lasers, and extend the results for arbitrary seed laser envelope and phase.
	Slides MOOCI01 [2.534 MB]

TUOAI02	Hard X-ray Self-Seeding at the LCLS
	R.R. Lindberg, W. Berg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents ANL, Argonne, USA J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, D.R. Walz, J.J. Welch, J. Wu, D. Zhu SLAC, Menlo Park, California, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia P. Emma LBNL, Berkeley, California, USA S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 The Linac Coherent Light Source (LCLS) has produced extremely bright hard x-ray pulses using self-amplified spontaneous emission (SASE) since 2009. In SASE, the electron beam shot noise initiates the FEL gain, resulting in output radiation characterized by poor temporal coherence and a fluctuating spectrum whose normalized width is given by the FEL bandwidth. Recently, colleagues at DESY suggested a self-seeding scheme for the LCLS to reduce the bandwidth. Here, the SASE produced in the first half of the undulator line is put through a simple diamond-based monochromator; the resulting monochromatic light trailing the main SASE pulse is used to seed the FEL interaction in the downstream undulators. We report on the experimental results implementing such a scheme at the LCLS, in which we have measured a reduction in bandwidth by a factor of 40-50 from that of SASE at 8-9 keV. The self-seeded FEL operates close to saturation, with the maximum output energy approximately equal to that with no seeding for low charge. The observed level of power fluctuations in the seeded output is presently rather large, and future plans focus on discovering their origins and reducing their magnitude. Geloni, V. Kocharyan ,and E.L. Saldin, DESY 10-133, arXiv:10⁰⁸.3036 (2010)
	Slides TUOAI02 [22.104 MB]

THPD50	Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-based Light Sources	646
	D.F. Ratner, A. Chao SLAC, Menlo Park, California, USA Y. Jiao IHEP, Beijing, People's Republic of China
	Modern accelerator light sources are based on either linac-FELs or storage rings. The linac-FEL type has high brilliance (microbunched beam) but low repetition rate. The storage ring type has high repetition rate (rapid beam circulation) but low brilliance. We propose to explore the feasibility of a microbunched beam in a storage ring that promises high repetition rate and high brilliance. The steady-state microbunched (SSMB) beam in a storage ring could provide CW sources for THz, EUV, or soft X-rays. We review several recently proposed SSMB concepts as promising directions for high brightness, high repetition rate light sources of the future.