FEL2014 - List of Authors (Zholents, A.)

Paper

Title

Page

Broadly Tunable Free-Electron Laser for Four-wave Mixing Experiments with Soft X-ray Pulses

461

G. Marcus
SLAC, Menlo Park, California, USA
G. Penn
LBNL, Berkeley, California, USA
A. Zholents
ANL, Argonne, Illinois, USA

This paper examines a FEL design for the production of three soft x-ray pulses from a single electron beam suitable for four-wave mixing experiments. Independent control of the wavelength, timing and angle of incidence of the three ultra-short, ultra-intense pulses with exquisite synchronization is critical. A process of selective amplification where a chirped electron beam and a tapered undulator are used to isolate the gain region to only a short fraction of the electron beam is explored in detail. Numerical particle simulations are used to demonstrate the essential features of this scheme in the context of the LCLS-II design study.

THP039

Commissioning of the Photo-Cathode RF Gun at APS

803

Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents
ANL, Argonne, Ilinois, USA

A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations.
Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

FRB02

A Collinear Wakefield Accelerator for a High Repetition Rate Multi-beamline Soft X-ray FEL Facility

993

A. Zholents, W. Gai, R.R. Lindberg, J.G. Power, Y.-E. Sun
ANL, Argonne, Ilinois, USA
C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
C. Li, C.-X. Tang
TUB, Beijing, People's Republic of China
D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Supported by U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and by the U.S. Department of Energy Laboratory LDRD program at Los Alamos National Laboratory.
A concept is presented for a multi beamline soft x-ray free-electron laser (FEL) facility where several FEL undulator lines are driven by an equal number of high repetition rate single-stage collinear wakefield accelerators (CWA). A practical design of the CWA, extending over 30 meters and embedded into a quadrupole wiggler, is considered. The wiggler’s structure of alternating focusing and defocusing quadrupoles is used to control single-bunch breakup instability. It is shown that practical restrictions on the maximum attainable quadrupole field limit the maximum attainable charge in the drive bunch whose sole purpose is to produce a high accelerating field in the CWA for the following main bunch. It is also pointed out that the distance between drive and main bunches varies along the accelerator, causing a measurable impact on the energy gain by the main bunch and on the energy spread of electrons in it. Means to mitigate these effects are proposed and results are presented for numerical simulations demonstrating the main bunch with plausible parameters for FEL application including a relatively small energy spread. Finally, results are presented for the expected FEL performance using an appropriately chosen undulator.

Slides FRB02 [6.512 MB]

Paper	Title	Page
TUP033	Broadly Tunable Free-Electron Laser for Four-wave Mixing Experiments with Soft X-ray Pulses	461
	G. Marcus SLAC, Menlo Park, California, USA G. Penn LBNL, Berkeley, California, USA A. Zholents ANL, Argonne, Illinois, USA
	This paper examines a FEL design for the production of three soft x-ray pulses from a single electron beam suitable for four-wave mixing experiments. Independent control of the wavelength, timing and angle of incidence of the three ultra-short, ultra-intense pulses with exquisite synchronization is critical. A process of selective amplification where a chirped electron beam and a tapered undulator are used to isolate the gain region to only a short fraction of the electron beam is explored in detail. Numerical particle simulations are used to demonstrate the essential features of this scheme in the context of the LCLS-II design study.

THP039	Commissioning of the Photo-Cathode RF Gun at APS	803
	Y.-E. Sun, J.C. Dooling, R.R. Lindberg, A. Nassiri, S.J. Pasky, H. Shang, T.L. Smith, A. Zholents ANL, Argonne, Ilinois, USA
	A S-band RF gun is recently RF conditioned and commissioned at APS, Argonne. In this paper we report the high-power RF conditioning process of the gun. Dark currents are monitored during the RF conditioning and found to be less than 150pC. Following the RF conditioning, photo-electron beams are generated from the gun and the copper cathode quantum efficiency is monitored. We study the quantum efficiency as gun gradient varies and vacuum condition improves. Photo-electron beam enery and emittance are measured as RF gun gradient and solenoid, as well as drive-laser conditions are varied. Finally we compare our experimental results with numerical simulations. Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

FRB02	A Collinear Wakefield Accelerator for a High Repetition Rate Multi-beamline Soft X-ray FEL Facility	993
	A. Zholents, W. Gai, R.R. Lindberg, J.G. Power, Y.-E. Sun ANL, Argonne, Ilinois, USA C.-J. Jing, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA C. Li, C.-X. Tang TUB, Beijing, People's Republic of China D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Supported by U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and by the U.S. Department of Energy Laboratory LDRD program at Los Alamos National Laboratory. A concept is presented for a multi beamline soft x-ray free-electron laser (FEL) facility where several FEL undulator lines are driven by an equal number of high repetition rate single-stage collinear wakefield accelerators (CWA). A practical design of the CWA, extending over 30 meters and embedded into a quadrupole wiggler, is considered. The wiggler’s structure of alternating focusing and defocusing quadrupoles is used to control single-bunch breakup instability. It is shown that practical restrictions on the maximum attainable quadrupole field limit the maximum attainable charge in the drive bunch whose sole purpose is to produce a high accelerating field in the CWA for the following main bunch. It is also pointed out that the distance between drive and main bunches varies along the accelerator, causing a measurable impact on the energy gain by the main bunch and on the energy spread of electrons in it. Means to mitigate these effects are proposed and results are presented for numerical simulations demonstrating the main bunch with plausible parameters for FEL application including a relatively small energy spread. Finally, results are presented for the expected FEL performance using an appropriately chosen undulator.
	Slides FRB02 [6.512 MB]