Development of a Gd2Si2O7 (GPS) Scintillator-Based Alpha Imaging Detector for Rapid Plutonium Detection in High-Radon Environments

We developed a Gd2Si2O7 (GPS) scintillator-based alpha imaging detector and demonstrated its effectiveness by evaluating the actual Pu particle and Rn-222 progeny. The GPS scintillator plate was prepared by a sintering method. The outer dimensions of the GPS scintillator plate were 5 x 5 cm, and the scintillator layer was approximately 50 mu m on a 3-mmthick high-transparency glass. The plate was optically coupled to a position-sensitive photomultiplier tube (Hamamatsu H8500, Hamamatsu, Japan) with silicone grease. The developed imaging detector exhibited good uniformity; Pu particle activities were accurately evaluated at 14 different positions and the difference in activity was within +/- 6%. The radon-222 progeny counts were reduced by 65.3% by applying an energy window. Although the Pu/Rn-222 progeny activity ratio was 1/51, the Pu particle was successfully identified among the Rn-222 progeny within the 5-min measurement time. The imaging detector has an excellent ability for detecting Pu among the Rn-222 progeny. Thus, this detector is useful for alpha contamination monitoring in high-radon-background environments.