Solid-State Nuclear Detectors for Monitoring Low Levels of Tritium

Low noise silicon avalanche photodiodes (APDs) with ultra thin surface dead layers have been developed for detecting tritium beta particles. Unlike the present windowless proportional counters and liquid scintillation techniques this alternative requires no liquid or flowing gases and has the reliability and compactness of solid-state detector technology. We have carried out detector research to study and optimize the physical and electrical properties of APDs for nuclear spectroscopy. A particular emphasis has been placed on reducing the noise and surface dead layer of large area avalanche photodiodes (1 cm diameter) in order to maximize the quantum efficiency for detecting low energy betas, as well as to investigate the effects of changing temperature, bias, and leakage current on avalanche gain, signal-to-noise and tritium detection quantum efficiency.