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Accession Number DE2012-1045173
Title Identifying Longitudinal Jitter Sources in the LCLS Linac.
Publication Date Jul 2012
Media Count 3p
Personal Author A. Brachmann F. J. Decker J. Craft R. Akre
Abstract The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser (FEL) with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.
Keywords Electron beams
Free electron lasers
Light sources
Linear accelerators
Phase space
Stanford Linear Accelerator Center

Source Agency Technical Information Center Oak Ridge Tennessee
NTIS Subject Category 46 - Physics
Corporate Author Stanford Linear Accelerator Center, CA.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1303
Contract Number DE-AC02-76SF00515

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