High Data-Rate Neutron-Sensitive Pixelated Detector Using Silicon Photomultiplier

We report on the design and performance of a neutron-sensitive pixelated detector using an array of silicon photomultiplier (SiPM) sensors. The proof-of-concept design consists of an 8 × 8 array of SiPM sensors coupled with an 8 × 8 array of ⁶Li-enriched glass scintillator (GS20) cubes. Each scintillator cube, of size 2 mm × 2 mm × 2 mm, is placed directly over each element in the sensor array. Each sensor is read out and processed using a simple comparator for pulse height discrimination. Individual counts are then recorded using a Xilinx ZYNQ-based system on chip. Tests performed at the Double-Axis Diffractometer (2X-C) and the High-Resolution Neutron Powder Diffractometer (PSD) beamlines at Missouri University Research Reactor (MURR) show a linear response of individual sensor element up to 100 kHz over an area of 0.2 cm × 0.2 cm, which is equivalent to 2.5 MHz/cm². The detector efficiency at a neutron wavelength of 4.1 A was measured to be 74.6% relative to the̊ detection efficiency of a 1-inch diameter 10-atm ³He gas detector. The pixel crosstalk was estimated to be less than 3%. The gamma sensitivity was measured to be 1 × 10^-3 using calibrated ⁶⁰Co gamma source at the optimal discriminator setting of the detector.