Author: Tanaka, H.
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.  
slides icon Slides MOAL2 [59.364 MB]