• H. Maesaka, S.I. Inoue, Y. Otake
  RIKEN/SPring-8, Hyogo
• S. Matsubara, Y. Tajiri
  JASRI/SPring-8, Hyogo-ken

To measure the femtosecond bunch length (10 - {10}00 fs) of the XFEL facility at SPring-8, we developed a coherent synchrotron radiation (CSR) monitor and a streak camera system. A pyro-electric detector was employed to measure the CSR intensity, since the CSR frequency region is THz or far infra-red. The CSR source is a dipole magnet of a chicane section. For the streak camera, we used Hamamatsu FESCA200, which has 200 fs resolution. The temporal structure of the optical transition radiation (OTR) from a metal mirror is observed by this camera. By using these monitors, the bunch length dependence was measured as a function of the rf phase of an S-band accelerator upstream of the bunch compressor at the SCSS test accelerator. A strong correlation between the CSR intensity and the S-band phase was observed. The CSR intensity was small at a debunching phase and the intensity increased as the rf phase was shifted to the bunching direction. Finally, it decreased in the over-bunching region. The bunch length data from the streak camera also had the same tendency. Thus, the bunch compression characteristics were appropriately measured and were consistent with our simulation results.