SSPM Detector for Polarized Target Scintillator Readout

Nuclear physics investigations require photodetectors that operate in harsh conditions (e.g., temperatures of 5 K and below, and magnetic fields greater than 1 T); yet existing methods of photodetection cannot provide the needed quality of data at a reasonable cost. This project will develop a photodetector that will tolerate these conditions and can be made in a commercially available, low-cost semiconductor fabrication process. Phase I demonstrated the operation of CMOS photodetectors at 5 K. The prototype photodiodes showed high gains at these low temperatures when operated below breakdown, or in proportional mode. The detailed radiometric performance indicated that a photodetector operated in proportional mode can meet the demands of experiments in these harsh environments. In Phase II, a prototype instrument will be developed to collect data in a nuclear physics experiment. The device will consist of solid-state photodiodes operated in proportional mode, and the instrument will be optimized in terms of gain, energy resolution, dark noise, and heat load. Once optimized, the photodetector will be packaged to allow for robust and sensitive operation for multiple applications. Commercial Applications and Other Benefits as described by the awardee: A photodetector that can operate at low temperatures ( 10%) would be a marketable device for novel scientific experiments that operate under these extreme conditions. The detector also should find use with positron emission topography at cryogenic temperature, or as LXe detectors for detecting Weakly Interacting Massive Particles.