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Title: A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions

Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations--particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL
 [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. Jefferson Lab, Newport News, VA
  2. Brookhaven National Lab, Upton, NY
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-ACC-15-2066; DOE/OR/23177-3535
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: IPAC 2015, 3-8 May 2015. Richmond, Virginia
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States