Development of omnidirectional gamma-imager with stacked scintillators

In the severe accident at nuclear power plant, a rapid measurement of radioactive fallout is required. So we have developed a Compton imager with high efficiency and omnidirectional sensitivity. Three dimensional position resolutions were evaluated about several kinds of scintillators. The all-directional imaging was demonstrated by the simulation of detection of 137 Cs point source. Imaging quality with angle resolution of 28° and detection efficiency of 1.1% was estimated.