Assessing Age Effects on Pulse Shape Discrimination Capabilities of Organic Glass Scintillators

Organic glass scintillators (OGS) are useful tools in nuclear engineering for their ability to detect both fast neutrons and gamma-rays. However, over time, this material can undergo recrystallization which can impact detection efficiency and pulse shape discrimination (PSD) capabilities. An understanding of such changes is necessary for long-term applications of these materials. The University of Michigan Scintillator Laboratory is equipped [1]with capabilities to melt-cast Sandia National Laboratories’ small-molecule organic glass scintillators. Fifteen 6.35 x 6.35 x 6.35 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> OGS cube scintillators were melt-cast from OGS powder. Half of these were exposed to 50 °C for 448 hours to induce surface crystallization through accelerated aging. PVA coatings were used to help slow this process in several of these scintillators. Using the same readout and electronic system of a DT5730S CAEN digitizer and a 7.62 cm diameter photomultiplier tube, we measured a Cf-252 source with each cube individually to evaluate their pulse shape discrimination (PSD) capabilities. These measurements showed less than a 6% decrease in light output across all samples following aging. PSD capabilities are not greatly impacted with an average percent change of figure of merit in the 0.25 to 0.75 MeVee energy range.