Author: Ishikawa, T.
Paper Title Page
MOAL2 The First Demonstration of EOS 3D-BCD Monitor to Maximize 3D-Overlapping for HHG-Seeded FEL 1
 
  • H. Tomizawa, T. Ishikawa, K. Ogawa, H. Tanaka, M. Yabashi
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Matsubara, Y. Okayasu, T. Togashi
    JASRI/SPring-8, Hyogo, Japan
  
  In FEL seed­ing as a full-co­her­ent light source, a high hit rate of suc­cess­fully seeded FEL pulses is re­quired. Pre­cise mea­sure­ments of the elec­tron bunch charge dis­tri­b­u­tion (BCD) and its ar­rival tim­ing are cru­cial keys to max­i­mize and keep 3D over­lap­ping be­tween the high-or­der har­mon­ics (HH) laser pulse and elec­tron bunch. We con­structed a rel­a­tive tim­ing drift mon­i­tor based on EOS, which mea­sured the tim­ing dif­fer­ences be­tween the seed­ing HH-laser pulse and the elec­tron bunch, using a com­mon ex­ter­nal laser source of both HH-dri­ving and EO-prob­ing pulses. The feed­back sys­tem of tim­ing drift was re­al­ized with real-time data pro­cess­ing of EO-sig­nal spec­tra. Our sys­tem re­al­ized sta­ble seeded FEL op­er­a­tion with a hit rate of 30%. The 3D-BCD mon­i­tor en­ables non-de­struc­tive mea­sure­ments of the lon­gi­tu­di­nal and trans­verse BCD at the same time. The trans­verse de­tec­tion can be used to con­trol the rel­a­tive point­ing be­tween HH-pulse and elec­tron bunch. We also ver­i­fied this trans­verse de­tec­tion with mul­ti­ple EO crys­tals at the EUV-FEL ac­cel­er­a­tor. Our next tar­get for tem­po­ral res­o­lu­tion is 30 fs, with an oc­tave-band EO-prob­ing for DAST crys­tals, aim­ing FEL seed­ing in the soft X-ray re­gion.  
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