Gamma spectroscopy using a silicon photomultiplier and a scintillator

Silicon photomultipliers are of great interest for scintillation light detection in gamma spectroscopy, due to their large gain and high speed. In this article we report about the use of a silicon photomultiplier for radiation detection and gamma spectroscopy. It is our goal to understand silicon photomultipliers to the extent that we could use them in imaging instrumentation for applications in nuclear medicine. We measure gain of up to 10⁶, and pixel dark count rate of a few MHz related to the leakage current of about 1 muA. Using an LED pulser, we measure the signal risetime of less than a few nano-seconds, and 300-ps rms jitter relative to a photomultiplier tube. We use CsI:Tl and LSO:Ce scintillators and measure energy spectra from radionuclides. In CsI:Tl we measure an energy resolution of 32% FWHM at 122 keV from Co-57, and extrapolate a resolution of 30% FWHM at 140 keV. We observe reasonably good energy spectra from LSO:Ce scintillators. Similar energy spectra were obtained with a photomultiplier tube as a reference