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内容記述 |
In gamma-ray astronomy, detectors with high sensitivity in the MeV region, which has not yet been explored, is expected to be flown in space in the future. In UVSOR synchrotron facility a MeV gamma-ray pulse source based on inverse Compton scattering (ICS) has been developed for user applications such as positron annihilation spectroscopy and gamma-ray detector evaluation. The ICS gamma rays possess other characteristics such as quasi-monochromatic (dE/E = a few %), highly polarized (~100%), and low divergence angle (<1 mrad). Linearly polarized gamma rays are generated by scattering of a linearly polarized laser and electron beam, and their polarization axis can be tuned to any angle by changing the angle of a half waveplate. Moreover, circularly polarized gamma rays can be generated using a circularly polarized laser, and their helicity can be easily inverted. The highly polarized and energy tunable gamma-ray sources are ideal as a light source for measurements of directional sensitivity, polarization, and energy for astronomical gamma-ray detectors. In this conference, details of the UVSOR’s gamma-ray source, including energy tunability, energy spread, and polarization characteristics, will be presented. The most basic polarization property of ICS gamma rays is that the polarization of linearly and circularly polarized gamma rays varies with the position of the beam cross section. The results of polarization measurements using a Compton polarimeter are described. In addition, the spatial intensity distribution and polarization characteristics of gamma rays generated by lasers with axially symmetric polarization states such as radial and azimuthal polarization, which have not been investigated theoretically or experimentally, will also be presented. |
