  We compared the performance of a SiPM array and a PMT in a laboratory setting
using a single 5.08x5.08-cm cylindrical sodium iodide scintillating crystal.
Photomultiplier tubes (PMTs) are the most commonly used device to monitor
scintillating materials for radiation detection purposes. The systems are
sometimes limited by disadvantages in the PMTs that may degrade their
performance, including temperature dependence and variation with magnetic
field. Instrumentation engineering must also contend with a potentially large
volume relative to the active scintillator volume, fragility, and high voltage
requirements. One possible alternative is an array of silicon photomultipliers
(SiPMs). Measurements were made with a 5.04x5.04-cm sensL J-series SiPM array
and a 7.62cm Hamamatsu PMT. We demonstrated how the SiPM bias can be
sufficiently altered to remove the effects of temperature variation encountered
in environments where nuclear safeguards work is often performed. Finally, we
evaluated a method of determining enrichment levels of ${}^{235}U$ at various
levels and shielding configurations, using both the PMT-mounted and
SiPM-mounted scintillator.
