Neutron detector development for high-rate neutron reflectometry at the Second Target Station of Oak Ridge National Laboratory

The Second Target Station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) is expected to produce a neutron source that is the brightest in the world, having a significantly higher peak brightness compared to the First Target Station (FTS), where the reflectometry instruments already fall short of being able to handle the highest available flux by a factor of ~100. The neutron reflectometers at the SNS FTS are not suitable for the reflectometers planned for the SNS STS because of its unprecedentedly high peak brightness and the already limited capabilities of these instruments at high count rates. Furthermore, the high rate instruments that are now under development are expected to underperform with regard to gamma sensitivity, meaning that signal-to-noise will be reduced and they will be unable to measure weaker reflectance phenomena in the presence of the significant prompt gamma flash at SNS. To address these challenges, we conducted research to advances associated instruments, techniques, and capabilities for the SNS STS reflectometers. More specifically, we investigated the development of a scalable, 2-D positive-sensitive, pixelated, scintillator-based neutron detector module based on a newly developed scintillator. The work has potential for impact on future neutron reflectometry instruments and neutron science performed at the SNS STS. In particular, the improved background rejection capability of the developed detector could extend the available experimental dynamic Q range, allowing it to measure weak reflectance phenomena.