• S.M. Matsubara
  RIKEN/SPring-8, Hyogo
• A. Maekawa
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken
• H. Tomizawa
  JASRI/SPring-8, Hyogo-ken

High-brightness electron bunches are required with low slice emittance and bunch length of 30 fs (FWHM) in a targeting lasing part for XFEL/Spring-8. In order to obtain maximum brightness, it is very important to measure 3D bunch charge distribution (BCD) in real-time for future X-ray light sources (XFEL, ERL, etc). Therefore, we are developing a single-shot, non-destructive, and real-time 3D-BCD monitor based on Electro-Optical Sampling with a manner of spectral decoding. The monitor system requires for a probe laser source to realize a higher temporal resolution. The laser source has broad spectrum of over 400 nm width and a linear-chirp of over 3,000 fs² to be few-ps pulse duration. Then, the shape in the frequency regions is rectangular. The liner-chirp is supplied by using a broadband AO-modulator (DAZZLER) which is possible to remove higher order dispersions. The laser pulses will be amplified to be micro-joule pulse-energy with a manner of NOPA. The laser source with such as the properties is mentioned in this report. We expect the feasibility of 20 fs temporal resolution by using this laser source with an organic crystal such as a DAST crystal.

• 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.