Scalability of Stilbene for Use in Nuclear Nonproliferation Applications

A new growth technique for stilbene scintillation crystals has been developed by LLNL that is capable of growing to larger sizes than traditional melt-based techniques. The goal of this study is to determine how stilbene’s neutron detection capabilities depend on the crystal thickness. Four stilbenes with thicknesses varying from 2.54 to 10.12 cm were used in measurements of 252Cf. Time-of-flight was used to assess the accuracy of the PSD, calculating the rate at which neutrons are misclassified as gamma rays, while geometry was used to determine the neutron intrinsic efficiency. It was found that neutron intrinsic efficiency increases from 17% to 38% with increasing length, although 35% efficiency was achievable with a 7.62-cm crystal. Meanwhile, gamma misclassification rate stays relatively constant at 4 × 10-4 for crystals with thicknesses up to 7.62 cm and increases to 1 × 10-3 for the 10.16-cm crystal.