Small Prototype Gamma Spectrometer Using CsI(Tl) Scintillator Coupled to a Solid-State Photomultiplier

Small solid-state photomultipliers (SSPMs) are an alternative scintillator light-detection technology to traditional photomultiplier tubes that offer advantages such as lower bias voltages and insensitivity to magnetic fields. A digital spectrometer using a commercially available SSPM was constructed and characterized at Oregon State University as a prototype for small, highly-mobile, low-power, robust spectroscopy devices. The SSPM has over 19,000 microcells in a photo-sensitive area of 6.32 × 6.32 mm and was coupled to 6 × 6 × 10 mm reflectively-coated CsI(Tl) crystals. The rest of the spectrometer consists of a fast preamplifier and 200 MHz, 12-bit digital pulse processor based around a field-programmable gate array (FPGA). The efficiency, resolution, linearity, and peak-to-Compton ratio of the system were characterized.