Laser Compton Scattering (LCS) is a technique to produce quasi-monochromatic X-rays and gamma rays by colliding a laser with a high-energy electron beam produced by an accelerator. Although LCS light sources are expected to produce photons of the same quality in a small (6m x 8m) device as those from large synchrotron radiation facilities , the low number of scattered photons is an issue for practical use. To solve this problem, we have developed an optical cavity to generate colliding lasers with high repetition rate and high peak power. However, the operation of an optical cavity in an accelerator environment with high noise limits the stored optical power by maintaining resonance through resonator length control. Therefore, we have devised and are developing a self-resonating optical cavity in which the resonance is maintained spontaneously by connecting the optical storage resonator and the laser oscillator in a closed loop. In this talk, I will report on the current status of self-resonating optical cavity and its temperature dependence.

Our laboratory has been studying about polymer electrolyte membrane (PEM) for polymer electrolyte fuel cell (PEFC) by irradiation graft polymerization using electron beam accelerator. Irradiation graft polymerization can reduce the production cost of the PEM compared with the current product, perfluoro-sulfonic acid (PFSA) ionomer such as Nafion®︎ by DuPont. We have two methods to fabricate high-performance PEMs using the accelerator. One is to give the micro-structure of hydrophilic and hydrophobic region to the PEM. The other is to generate the concentration gradient of hydrophilic region inside of the PEM. Both methods were able to generate high power density as much as Nafion®︎. In previous study, we used ion beam to give these characteristics. Ion beam has highly straightness and easy to create micro-structure and the concentration gradient of hydrophilic region inside of the PEM. But, its production equipment costs too much. Therefore, in this study, we use electron beam that production equipment costs less than ion beam and fabricate the PEM which has above both methods for advanced application of the electron beam accelerator.