Novel Method of Temperature Stabilization for SiPM-Based Detectors

One of the drawbacks of silicon-based photomultipliers is variation of performance with even small temperature fluctuations. The purpose of this work is to investigate a novel method of temperature stabilization of SiPM-based imaging device. Our prototype cooling system utilizes optically transparent cooling fluid as means of removing heat from the light detector and spreading scintillation light among several SiPM units. Cooled liquid passes through a 2 mm opening between two Mylar sheets. The Mylar sheets are held together with an aluminum frame. An array of SiPMs and an array of LYSO scintillation crystals are attached to opposite sides of the cooling light guide. Temperature uniformity of the optical surface was evaluated with an infrared camera. A temperature gradient of 0.09 degrees C/cm was measured along the direction of the coolant flow. The system was tested with a 5 x 5 array of Hamamatsu S10943 SiPMs coupled to a 16 x 16 matrix of 1.5 x 1.5 x 10 mm LYSO crystals. Testing procedures included evaluation of temperature dependence of detector gain, integrated noise, ability to resolve individual crystals and energy resolution. Detector gain varied by 9.3% over the range of 5 degrees C. Energy resolution change of 5% was observed over the same temperature range. Integrated noise contribution showed moderate increase of 2.2% over the range of 7 degrees C. The separation of individual crystals was found adequate with only a weak dependence of peak-to-valley contrast ratios on temperature. An assessment of performance stability at constant temperature revealed 0.2% variation in gain and 0.7% variation in energy resolution during an hour-long acquisition. It is concluded that the proposed method is a viable option for cooling and temperature stabilizing of SiPM-based systems.