Development of gamma ray sources and their application studies in UVSOR-III

Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya  ; Endo, Shunsuke   ; Zen, H.*; Shizuma, Toshiyuki*

At UVSOR, a synchrotron radiation facility at the Institute for Molecular Science, gamma rays are generated by inverse Thomson scattering. Compared to gamma rays generated from radioisotopes and bremsstrahlung gamma rays, it has excellent features such as variable energy, quasi-monochromatic, low background, and high directivity. It is also possible to generate polarized gamma rays by using a polarized laser. Using this gamma ray, nuclear physics experiments such as isotope imaging by nuclear resonance fluorescence scattering, evaluation of gamma ray detectors, and research on material analysis by gamma ray-induced positron annihilation spectroscopy are being carried out. Positron annihilation spectroscopy is a powerful method that can analyze defects of sub-nm to several nm such as monatomic vacancies. Positrons can also be generated from gamma rays by pair production. By irradiating the sample with gamma rays, positrons are generated inside the sample, and it is possible to analyze defects in a bulk sample with a thickness of several cm. At this year's meeting, we will present the development of gamma ray sources in UVSOR, the magnetic Compton scattering experiment of circularly polarized gamma rays, the development of gamma ray-induced positron annihilation spectroscopy, and the development of measurement technology for spin-polarized positrons using circularly polarized gamma rays.