Author: Tsai, C.-Y.
Paper Title Page
TUPRB062 Coherence Time Characterization for Self-Amplified Spontaneous Emission Free-Electron Lasers 1820
 
  • G. Zhou, Y. Jiao, J.Q. Wang
    IHEP, Beijing, People’s Republic of China
  • T.O. Raubenheimer, J. Wu
    SLAC, Menlo Park, California, USA
  • C.-Y. Tsai
    HUST, Wuhan, People’s Republic of China
  • C. Yang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  One of the key challenges in scientific researches based on free-electron lasers (FELs) is the characterization of the coherence time of the ultra-fast hard x-ray pulse, which fundamentally influences the interaction process between x-ray and materials. Conventional optical methods, based on autocorrelation, is very difficult to realize due to the lack of mirrors. Here, we experimentally demonstrate a conceptually new coherence time characterization method and a coherence time of 174.7 attoseonds has been measured for the 6.92 keV FEL pulses at Linac Coherent Light Source. In our experiment, a phase shifter is adopted to control the cross-correlation between x-ray and microbunched electrons. This approach provides critical temporal coherence diagnostics for x-ray FELs, and is decoupled from machine parameters, applicable for any photon energy, radiation brightness, repetition rate and FEL pulse duration, etc.
The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB062  
About • paper received ※ 01 May 2019       paper accepted ※ 28 May 2019       issue date ※ 21 June 2019  
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TUPTS047 Improvement of 6D Brightness by a 1.4-cell Photocathode RF Gun for MeV Ultrafast Electron Diffraction 2033
SUSPFO069   use link to see paper's listing under its alternate paper code  
 
  • Y. Song
    Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China
  • K. Fan, C.-Y. Tsai, Y.T. Yang
    HUST, Wuhan, People’s Republic of China
  • J. Yang
    ISIR, Osaka, Japan
  
  Recent research indicates that ultrafast electron diffraction and microscopy (UED/M) have unprecedented potential in probing ultrafast dynamic processes, especially in organic and biological materials. However, reaching the required brightness while maintaining high spatiotemporal resolution requires new design of electron source. In order to produce ultrashort electron beam with extreme high brightness, a 1.4-cell RF gun is being developed to reach higher acceleration gradient near the photocathode and thus suppress the space charge effect in the low energy region. Simulation of the 1.4-cell RF photocathode gun shows considerable improvement in bunch length, emittance and energy spread, which all lead to better temporal and spatial resolution comparing to traditional 1.6-cell RF photocathode gun. The results demonstrate the feasibility of sub-ps temporal resolution with normalized emittance less than 0.1 πmm·mrad while maintaining 1 pC electron pulse.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS047  
About • paper received ※ 24 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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