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Title: Generation and measurement of velocity bunched ultrashort bunch of pC charge

In this paper, we discuss the velocity compression in a short rf linac of an electron bunch from a rf photoinjector operated in the blowout regime. Particle tracking simulations shows that with a beam charge of 2 pC an ultrashort bunch duration of 16 fs can be obtained at a tight longitudinal focus downstream of the linac. A simplified coherent transition radiation (CTR) spectrum method is developed to enable the measurement of ultrashort (sub-50 fs) bunches at low bunch energy (5 MeV) and low bunch charges (<10 pC). In this method, the ratio of the radiation energy selected by two narrow bandwidth filters is used to estimate the bunch length. The contribution to the coherent form factor of the large transverse size of the bunch suppresses the radiation signal significantly and is included in the analysis. The experiment was performed at the UCLA Pegasus photoinjector laboratory. The measurement results show bunches of sub-40 fs with 2 pC of charge well consistent with the simulation using actual experimental conditions. These results open the way to the generation of ultrashort bunches with time-duration below 10 fs once some of the limitations of the setup (rf phase jitter, amplitude instability and low fieldmore » in the gun limited by breakdown) are corrected.« less
 [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [2]
  1. Tsinghua Univ., Beijing (China)
  2. Univ. of California, Los Angeles, CA (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Published Article
Journal Name:
Physical Review Special Topics. Accelerators and Beams
Additional Journal Information:
Journal Volume: 18; Journal Issue: 3; Journal ID: ISSN 1098-4402
American Physical Society (APS)
Research Org:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
National Science Foundation (NSF); National Natural Science Foundation of China (NNSFC); USDOE Office of Science (SC)
Country of Publication:
United States