FEL2012 - List of Authors (Penn, G.)

Paper	Title	Page
MOPD31	Injector Optimization for a High-repetition Rate X-ray FEL	89
	C. F. Papadopoulos, J.N. Corlett, P. Emma, D. Filippetto, G. Penn, J. Qiang, M.W. Reinsch, F. Sannibale, M. Venturini LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 In linac driven free electron lasers, the final electron beam quality is constrained by the low energy (<100 MeV) beam dynamics at the injector. In this paper, we present studies and the optimized design for a high-repetition (>1 MHz) injector in order to provide a high brightness electron beam. The design effort is also extended to multiple modes of operation, in particular different bunch charges. The effects of space charge and low energy compression on the electron beam brightness are also discussed for the different modes.

TUPD19	The Radiator-first HGHG Multi-MHz X-ray FEL Concept	273
	M.W. Reinsch, G. Penn LBNL, Berkeley, California, USA P.R. Gandhi, J.S. Wurtele UCB, Berkeley, California, USA
	A novel configuration for a high repetition rate X-ray FEL is investigated. In this scheme longitudinally coherent FEL pulses are obtained using a high gain harmonic generation (HGHG) system in which the seed power is generated in an FEL oscillator downstream of the HGHG section. The oscillator is powered by the spent beams that leave the HGHG radiator. Radiation from the oscillator is sent to the modulator of the HGHG section. The dynamics and stability of the radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft X-ray FEL in which the oscillator operates at 13.4 nm and HGHG radiation is generated at 1.34 nm. This radiator-first configuration potentially solves (i) the challenge of finding sources to seed future FELs driven by multi-MHz superconducting RF linacs and (ii) the difficulty of producing X-ray radiation with a bunch that exits an oscillator in the more "natural" configuration in which the oscillator precedes the radiator.

TUPD20	Soft X-ray SASE and Self-seeding Studies for a Next-generation Light Source	277
	G. Penn, P. Emma, D. Prosnitz, J. Qiang, M.W. Reinsch LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. In the self-seeding scheme, the longitudinal coherence and spectral density of an unseeded FEL can be improved [] by placing a monochromator at a location before the radiation reaches saturation levels, followed by a second stage of amplification. The final output pulse properties are determined by a complex combination of the monochromator properties, undulator settings, variations in the electron beam, and wakefields. We perform simulations for the output of SASE and self-seeded configurations for a soft x-ray FEL using both idealized beams and realistic beams from start-to-end simulations. These studies include cross-planar undulators dedicated to polarization control []. [] J. Feldhaus, E.L. Saldin, J.R. Schneider, E.A. Schneidmiller, and M.V. Yurkov, Optics Commun. 140 (1997) 341-352. [**] K.-J. Kim, Nucl. Instrum. Methods A 445 (2000) 329-332.

Paper

Title

Page

Injector Optimization for a High-repetition Rate X-ray FEL

89

C. F. Papadopoulos, J.N. Corlett, P. Emma, D. Filippetto, G. Penn, J. Qiang, M.W. Reinsch, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
In linac driven free electron lasers, the final electron beam quality is constrained by the low energy (<100 MeV) beam dynamics at the injector. In this paper, we present studies and the optimized design for a high-repetition (>1 MHz) injector in order to provide a high brightness electron beam. The design effort is also extended to multiple modes of operation, in particular different bunch charges. The effects of space charge and low energy compression on the electron beam brightness are also discussed for the different modes.

TUPD19

The Radiator-first HGHG Multi-MHz X-ray FEL Concept

273

M.W. Reinsch, G. Penn
LBNL, Berkeley, California, USA
P.R. Gandhi, J.S. Wurtele
UCB, Berkeley, California, USA

A novel configuration for a high repetition rate X-ray FEL is investigated. In this scheme longitudinally coherent FEL pulses are obtained using a high gain harmonic generation (HGHG) system in which the seed power is generated in an FEL oscillator downstream of the HGHG section. The oscillator is powered by the spent beams that leave the HGHG radiator. Radiation from the oscillator is sent to the modulator of the HGHG section. The dynamics and stability of the radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft X-ray FEL in which the oscillator operates at 13.4 nm and HGHG radiation is generated at 1.34 nm. This radiator-first configuration potentially solves (i) the challenge of finding sources to seed future FELs driven by multi-MHz superconducting RF linacs and (ii) the difficulty of producing X-ray radiation with a bunch that exits an oscillator in the more "natural" configuration in which the oscillator precedes the radiator.

TUPD20

Soft X-ray SASE and Self-seeding Studies for a Next-generation Light Source

277

G. Penn, P. Emma, D. Prosnitz, J. Qiang, M.W. Reinsch
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In the self-seeding scheme, the longitudinal coherence and spectral density of an unseeded FEL can be improved [*] by placing a monochromator at a location before the radiation reaches saturation levels, followed by a second stage of amplification. The final output pulse properties are determined by a complex combination of the monochromator properties, undulator settings, variations in the electron beam, and wakefields. We perform simulations for the output of SASE and self-seeded configurations for a soft x-ray FEL using both idealized beams and realistic beams from start-to-end simulations. These studies include cross-planar undulators dedicated to polarization control [**].
[*] J. Feldhaus, E.L. Saldin, J.R. Schneider, E.A. Schneidmiller, and
M.V. Yurkov, Optics Commun. 140 (1997) 341-352.
[**] K.-J. Kim, Nucl. Instrum. Methods A 445 (2000) 329-332.