A 1-dimensional γγ-ray position sensor based on GSO:Ce scintillators coupled to a Si strip detector

In order to improve a detection efficiency of the improved Fourier Synthesis imaging telescope, we are developing a one-dimensional γγ-ray position sensor using crystal scintillators coupled to a silicon strip detector (SSD). We have manufactured thin Gd2SiO5Gd2SiO5:Ce (GSO) scintillator plates with a dimension of 10mm×5mm×0.3mm. Twenty scintillator plates, with a light reflective sheet between adjacent plates, have been stacked into a block (stacked GSO). The SSD has 32 strip electrodes of 400μm pitch on its p-side, while its n-side common electrode is not metallic. The pulse height of the 32 channels are read out simultaneously by an analog ASIC. We coupled the stacked GSO to the n-side of the SSD with the GSO plates running parallel to the SSD strips. By irradiating the coupled device with γγ-rays from 137Cs and 22Na, we successfully obtained their spectra, and achieved a position resolution significantly finer than 1 mm.