Silicon Photomultipliers Embedded Into Melt-Cast Organic Glass Scintillator Assemblies

We present an alternative approach to organic scintillator detector fabrication and optical readout, in which silicon photomultipliers (SiPMs) are embedded directly into a cast-moldable organic scintillator. Organic glass scintillator formulations have properties that allow for cast-molding at temperatures below 200°C. This enables the freedom to construct arbitrary scintillator shapes, and interior photon detection is beneficial for shapes that either do not have an optimal coupling surface, or shapes with poor optical transport to a coupling surface. We provide a proof-of-principle demonstration by casting four Broadcom AFBR-S4N66P014M 6 mm × 6 mm SiPMs each into a 2.54 cm × 2.54 cm × 2.54 cm cube of organic glass scintillator. Potential performance impacts on the SiPMs due to the casting process are characterized by the noise properties before and after casting, including dark count rate, cross talk probability, and single photo-electron pulse height. We have measured small differences in noise properties resulting from the casting, none of which are expected to have a detrimental impact on overall performance. Finally, the light collection and neutron/gamma pulse shape discrimination performance for the four cubic assemblies is presented, further demonstrating functionality of the SiPMs as well as the performance of the particular organic glass scintillator formulation used.