Design and Characterization of an Optically Segmented Single Volume Scatter Camera Module

The optically segmented single volume scatter camera (OS-SVSC) aims to image neutron sources for nuclear nonproliferation applications using the kinematic reconstruction of elastic double-scatter events. We report on the design, construction, and calibration of one module of a new prototype. The module includes 16 EJ-204 organic plastic scintillating bars individually wrapped in Teflon tape, each measuring $0.5 {\mathrm {cm}}\times 0.5 {\mathrm {cm}}\times 20 {\mathrm {cm}}$ . The scintillator array is coupled to two custom silicon photomultiplier (SiPM) boards consisting of a $2\times 8$ array of SensL J-Series-60035 SiPMs, which are read out by a custom 16 channel DRS4 based digitizer board. The electrical crosstalk between SiPMs within the electronics chain is measured as $0.76\% \,\pm \,0.11\%$ among all 16 channels. We report the detector response of one module including interaction position, time, and energy, using two different optical coupling materials: EJ-560 silicone rubber optical coupling pads and EJ-550 optical coupling grease. We present results in terms of the overall mean and standard deviation of the $z$ -position reconstruction and interaction time resolutions for all 16 bars in the module. We observed the $1\sigma z$ -position resolution for gamma interactions in the 0.3–0.4 MeVee range to be 2.24 cm ± 1.10 cm and 1.45 cm ± 0.19 cm for silicone optical coupling pad and optical grease, respectively. The observed $1\sigma $ interaction time resolution is 265 ps ± 29 ps and 235 ps ± 10 ps for silicone optical coupling pad and optical grease, respectively.