Study of expected performance of the hard X-ray beam for the FEL-X project

We advance the FEL-X project and plan to install a new optical klystron for the infrared FELs within next year. The expected FEL gain at a wavelength of 10.6 μm is over 2% with the present electron-beam qualities in the storage ring NIJI-IV. Infrared FELs based on the fundamental and higher harmonics from the new optical klystron will generate hard X-ray beams with an energy of 0.1–2 MeV by the FEL-Compton backscattering process. Conventional light sources cannot provide sufficient amounts of photons in this energy region. The expected yield of the hard X-ray beam is 105–106 per second with an energy spread of 3%.