• S.M. Matsubara, A. Higashiya, N. Hosoda, S.I. Inoue, H. Maesaka, M. Nagasono, T. Ohshima, Y. Otake, K. Tamasaku, M. Yabashi
  RIKEN/SPring-8, Hyogo
• T. Togashi
  JASRI/SPring-8, Hyogo-ken

The SCSS test accelerator was constructed and user experiments using SASE-FEL light in an extreme-ultraviolet (EUV) region have been performed at SPring-8. It is necessary to distribute an accurate timing signal both to accelerator components and experimental instruments. We developed a trigger system targeted as a timing jitter of less than 100 fs. The jitter of the time difference between the reference timing signal and a beam-induced signal from an RF BPM cavity was measured. The jitter value was nearly 50 fs in rms. However, this value was measured with electron beams after C-band accelerator cavities and not measured with the SASE light pulses at the experimental end station. Therefore, we employed an in-vacuum fast photo diode in order to directly observe EUV light at a 60 nm and to detect the arrival timing at the end station. The measured time jitter was 2.5 ps in rms, which was limited by the photo diode. Even thorough the resolution of the time jitter did not reach to 50 fs, the system is still usable to verify trigger delay values for user experiments. This fast timing measurement using the in-vacuum photo diode is still a pioneer of optical technology in an FEL field.