Low-cost Individual Digital Dosimeters using Solid State Photomultipliers

U.S. forces working in low-level radiation environments have unsatisfactory choices for monitoring radiation exposure. A solid-state photomultiplier (SSPM) uses an array of silicon based avalanche photodiodes (APD) to collect light and produce a signal proportional to the amount of light collected. The ability to produce arrays of APD’s in a CMOS (Complimentary Metal Oxide Semiconductor) environment makes possible the production of miniaturized arrays integrated with the dosimeter electronics in a small silicon chip – the dosimeter on a chip. This technology represents a novel approach for collecting the signal produced from radiation incident on a scintillating material. Additionally, the small size of the integrated system allows large cost reduction after production scale-up. In Phase I, we demonstrated that a scintillating crystal coupled to an SSPM provides a basis for a low-cost, energy responsive, digital dosimeter that is sensitive to low radiation fields. We also demonstrated that Individual pixels operated at 10-15% above breakdown voltage are insensitive to temperature changes that can disable currently used dosimeters.