Development of a Scintillation-Based Detector for Ultracold Neutron Detection at PULSTAR

Ultracold neutrons (UCNs) are extremely low-energy neutrons that can be confined and manipulated for extended periods, enabling precise measurements of fundamental neutron properties such as the electric dipole moment (nEDM) and beta decay lifetime. Accurate detection of UCNs is essential for these experiments, as reliable counts and energy spectra help reduce systematic uncertainties. This project focused on developing and implementing a detection system for UCNs at the PULSTAR reactor at NC State University, using a scintillation-based method originally developed at Los Alamos National Laboratory. In this technique, UCNs interact with a scintillator screen composed of 10B and ZnS layers, producing light pulses upon neutron capture. These pulses are detected by a photomultiplier tube (PMT), which converts them into electrical signals that can be analyzed with an oscilloscope. A key part of the project involved designing and fabricating a custom housing for the PMT and its electronics, allowing for optimal alignment with the neutron guide and scintillation screen. The system will be calibrated using an alpha source, ²⁴¹Am, with known decay characteristics to determine detection efficiency before deployment at the UCN source. This work will contribute to the optimization of future neutron experiments requiring high-accuracy UCN detection.