Development of a detector with two photo-strip sensors and a crystal scintillator between sensors

Abstract

We fabricate single-sided strip sensors that are sensitive to light. The strip sensors are AC-coupled, which has coupling capacitors and bias resistors. The sensors are fabricated on a high resistivity and double-sided polished n-type silicon wafer. The sensor is designed as the single-side strip sensor but its backside (n-side) is modified to be sensitive to incoming light. This photo-strip sensor is designed to measure positions of incoming gamma ray and alpha particle. The photo-strip detector consists of two photo-strip sensors and one crystal scintillator. The sensors sandwiching opposite faces of a scintillator are oriented orthogonally to each other to provide two-dimensional position information. When particles enter a crystal, the scintillator light of a crystal is emitted and penetrates into the photo-strip sensors. The lights are then converted to electron-hole pairs in the sensors. The detector configuration provides not only two-dimensional position information, but also the depth of interaction (DOI). The DOI is given by comparing signal-to-noise ratio between the first and second photo-strip sensors. The fabricated sensors are electrically tested by varying bias voltages. The pulse heights of the detector are measured by using Am-241 alpha, Na-22 and Cs-137 gamma ray sources. The position information is obtained with one photo-strip sensor and the LYSO crystal scintillator by using Am-241 alpha source. An experiment to obtain two-dimensional position information with two photo-strip sensors and a scintillator crystal is on going.