• H. Zen, M. Adachi, M. Katoh
  UVSOR, Okazaki
• M. Hosaka, Y. Taira, N. Yamamoto
  Nagoya University, Nagoya
• T. Tanikawa
  Sokendai - Okazaki, Okazaki, Aichi

Coherent Harmonic Generation Free Electron Laser (CHG-FEL)* ** is a short pulse and coherent radiation source in vacuum ultra-violet regime. A measurement of CHG-FEL spectrum*** has been done and sidebands in spectrum were observed under an over-bunching condition. The measurement was done with chirped seed laser to avoid strong over-bunching of electron beam and to obtain larger pulse energy for high signal to noise ratio. In the paper ***, however, the seed laser chirping was not taken into account in the numerical analysis and the numerical results qualitatively agreed with experimental results but quantitatively not. We consider that the discrepancy was caused by the chirping property of the seed laser, and thus we have developed a time dependent simulation code which can deal the effect of seed laser chirping. Results of the code qualitatively agreed well with the shape of measured spectrum, not only bandwidth but also the sideband structure. And the code was used to evaluate the temporal and spectral property of CHG-FEL seeded by a chirped laser. The code revealed the spectral widening and chirped property of CHG-FEL pulse when the CHG-FEL is driven by a chirped seed laser.

* L. H. Yu et al., Phys. Rev. A 44, 5178 (1991).
** G. D. Ninno et al., Phys. Rev. Lett. {10}1, 053902 (2008).
***M. Labat et al., Phys. Rev. Lett. {10}2, 014801 (2009).

• T. Tanikawa
  Sokendai - Okazaki, Okazaki, Aichi
• M. Adachi, M. Katoh, J. Yamazaki, H. Zen
  UVSOR, Okazaki
• M. Hosaka, Y. Taira, N. Yamamoto
  Nagoya University, Nagoya

Light source technologies based on laser seeding are under development at the UVSOR-II electron storage ring. In the last FEL conference (FEL2009), we reported spectral measurements of coherent harmonic generation (CHG) seeded by the fundamental of Ti: Sapphire laser, in the region of vacuum-ultra violet (VUV). In this conference, we will report some systematic measurements such as the undulator gap dependence and seed laser power dependence. In the laser power dependence, we have observed a saturation of CHG intensity. The result will be compared with simulations. A seeding light source based on high harmonic generation (HHG) in rare gas is under development. The status will be reported.