Silicon Photomultiplier Arrays at TJNAF

Silicon photomultipliers have grown rapidly in the past few years as the detector of choice for highly compact photosensors with detection capabilities comparable to good vacuum photomultipliers and with the additional feature flow voltage requirement and immunity to magnetic fields. For various applications, the Radiation Detector and Imaging Group intends to make planar detectors based on silicon photomultiplier (SiPM) arrays. The eventual goal is to create an even greater channel reduction by using a resistive readout method so that only 4 channels per detector will be needed. This will allow for the creation of even larger detectors as

needed without creating additional complications in readout. The first concern with silicon photomultiplier arrays is the question of the uniformity of response across the 16 individual sensors. A small 18x18x5 mm3 array of pixilated LYSO scintillator was used as test light source. The 1x1 mm2 size of the pixels were known to be a challenging system to resolve successfully. The glass spacer was chosen experimentally in order to provide sufficient light sharing among the 16 sensors. A spacer of 3.2mm was found to be near optimal. The SiPM device was first explored at Jefferson Lab for nuclear physics detector system because of their immunity to magnetic fields. The devices are proving to have applications in Positron Emission Tomography applications.