• T. Togashi, K. Fukami, S. Matsubara, H. Ohashi, H. Tomizawa, T. Watanabe
  JASRI/SPring-8, Hyogo-ken
• M. Aoyama, K. Yamakawa
  JAEA/Kansai, Kyoto
• M.-E. Couprie
  SOLEIL, Gif-sur-Yvette
• T. Hara, T. Hatsui, T. Ishikawa, T.K. Kameshima, H. Kitamura, N. Kumagai, M. Nagasono, Y. Otake, T. Shintake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
  RIKEN/SPring-8, Hyogo
• A. Iwasaki, T. Okino, S. Owada, T. Sato, K. Yamanouchi
  The University of Tokyo, Tokyo
• F. Kannari
  Keio University, Kanagawa-ken
• K. Midorikawa, E. Takahashi
  RIKEN, Saitama
• H. Nakano
  NTT Corp., Kanagawa-ken
• A. Yagishita
  KEK, Tsukuba

A seeded FEL is the most promised way to generate fully coherent radiation in a short-wavelength　region. After the improvement of the laser and HHG system at the SCSS test accelerator, we have succeeded the amplification of the seed, for the first time, in the plateau region. The wavelength of the seed is 61.5 nm, which is the 13th harmonic of a Ti:Sa laser, and clear intensity increase and spectral narrowing by the FEL was observed. Although there still remains room for optimization of the transverse matching and synchronization of the seed, this result leads to realization of a fully coherent light source to users in VUV and soft x-ray regions.

Slides

• H. Tomizawa, H. Dewa, H. Hanaki, S. Matsubara, A. Mizuno, T. Taniuchi, K. Yanagida
  JASRI/SPring-8, Hyogo-ken
• T. Ishikawa, N. Kumagai
  RIKEN/SPring-8, Hyogo
• K. Lee
  University of Tokyo, Tokyo
• A. Maekawa, M. Uesaka
  UTNL, Ibaraki

We developed a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor based on Electro-Optical (EO) sampling with a manner of spectral decoding for XFEL/SPring-8. For the transverse detection, eight EO-crystals (Pockels effect) surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape passes through the EO-crystal. We plan to use an amorphous material which has only an even-order field dependence (Kerr effect) in donut shape without assembling eight conventional EO-crystals. The polarization axis of the probe laser should be radially distributed as well as the Coulomb field of the electron bunches. Since the signal intensity encoded at each crystal depends on the strength of the Coulomb field at each point, we can detect the transverse BCD. In the longitudinal detection, we use a prove laser with a broadband square spectrum (> 400 nm @ 800 nm) so that the temporal resolution is < 30 fs, if the pulse width of probe laser is 500 fs. In order to achieve 30-fs temporal resolution, we use an organic EO material, DAST crystal, which is transparent up to 30 THz. We report the first experimental results of our 3D-BCD monitor.