A SiPM-Based Gamma Spectrometer With Field-Programmable Energy Binning for Data-Efficient Isotope Analysis

A highly reconfigurable gamma spectrometer with a silicon photomultiplier detector and a custom integrated circuit (IC)-based multi-channel analyzer (MCA) is presented. The core of the MCA comprises a custom analog front-end IC and a piecewise-linear analog-to-digital converter (ADC) IC, both fabricated in a 180nm complementary metal-oxide-semiconductor (CMOS) process. Along with a field-programmable gate array (FPGA)-based digital back-end, the proposed architecture allows pulse-height analysis with reconfigurable analog gain and ADC resolution across the full dynamic range. Specifically, the piecewise-linear ADC can increase resolution in selected regions of interest while utilizing a fixed 7-bit digital word, thus enabling data reduction and spectrum feature enhancement. Reconfigurability also allows the MCA to be tuned for different scintillator materials used in the detector. The system architecture is introduced at a conceptual level, followed by detector and circuit-level MCA implementation details and design trade-offs. Several isotope spectra were recorded with two common scintillators, LYSO and CsI(Tl), spanning energy peaks from 32keV to 1.33MeV. Variable energy bin-widths were measured across different AFE gains, ranging from 3keV to 58keV for LYSO, and 1.4keV to 51keV for CsI(Tl), demonstrating the versatility of the proposed system and its ability to provide reconfigurable peak enhancement for radiation spectroscopy.