Optimization of Shape-Variable Gamma Camera to High-Dose-Rate Regions

To proceed with the decommissioning of Fukushima Daiichi Nuclear Power Station, it is necessary to visualize radioactive substances using a gamma camera in high-dose-rate regions inside nuclear reactor building. We developed an umbrella-shaped Compton camera, whose sensitivity distribution can be adjusted by changing its shape. When used on robot, moving distance robot reduced compared pinhole that sensitive only front surface. In addition, unlike omnidirectional specific direction increased, which expected expand degree freedom measurement. this study, characteristics system were evaluated through simulations and experiments for application high-level environment It estimated operate at dose rate approximately 2.68 mSv/h. Furthermore, we devised method compensate effect dead time SiPM (MPPC) region monitoring current drive power supply evaluating applicability high rates. This correction was validated case where photoelectric peak energy spectra fluctuated 60 keV due time.