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Title: LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields

Abstract

Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 0fs). To study the expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director, Office of Science. Office of Basic EnergySciences
OSTI Identifier:
860382
Report Number(s):
LBNL-58593
R&D Project: Z3SL01; TRN: US0504906
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Conference
Resource Relation:
Conference: 27th International Free Electron LaserConference, Stanford, CA, August 21-26, 2005
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; FREE ELECTRON LASERS; MAGNETIC FIELDS; PERFORMANCE; ROUGHNESS; SIMULATION; SPICES; WIGGLER MAGNETS; free-electron laser LCLS undulator wakefields

Citation Formats

Bane, Karl L.F., Emma, Paul, Huang, Heinz-Dieter Nuhn, Stupakov,Gennady, Fawley, William M., and Reiche, Sven. LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields. United States: N. p., 2005. Web.
Bane, Karl L.F., Emma, Paul, Huang, Heinz-Dieter Nuhn, Stupakov,Gennady, Fawley, William M., & Reiche, Sven. LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields. United States.
Bane, Karl L.F., Emma, Paul, Huang, Heinz-Dieter Nuhn, Stupakov,Gennady, Fawley, William M., and Reiche, Sven. Thu . "LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields". United States. https://www.osti.gov/servlets/purl/860382.
@article{osti_860382,
title = {LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields},
author = {Bane, Karl L.F. and Emma, Paul and Huang, Heinz-Dieter Nuhn and Stupakov,Gennady and Fawley, William M. and Reiche, Sven},
abstractNote = {Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 0fs). To study the expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Aug 25 00:00:00 EDT 2005},
month = {Thu Aug 25 00:00:00 EDT 2005}
}

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