We have developed a free electron laser (FEL) with a compact storage ring in the infrared region. The wavelength of infrared FEL light was in the region of 0.84–1.50 µm. The maximum power of the infrared FEL light transmitted through an optical cavity was about 1.6 mW, and the intracavity power was about 5W. We have also developed intensive quasi-monochromatic X-ray by using FEL Compton backscattering. The yield of the generated X-ray beam is roughly 10⁶ photons/s with the energy of 1.2-2.1 MeV. A prospective application of the present system would be a high-flux two-color light source of infrared light and an X-ray with variable energy.

If applied to the accelerator such as an energy-recovery linac, we would be able to realize a near monochromatic X-ray source with the energy of over 0.3 MeV and the yield of 10¹² photons/s, of the level not easily attainable even in a large synchrotron radiation facility. This type of X-ray beam would offer new measuring methods for magnetic material research, and would also contribute to the development of an ultra-high density magnetic recording system.