Neutron Dose Tolerant Solid-State Photomultiplier for Nuclear Imaging

Neutron reflectometry is a powerful tool in material science, and the Spallation Neutron Source at Oak Ridge National Laboratories is undergoing an upgrade to provide a high flux of neutrons on test samples to promote new discoveries. The higher intensity comes at a price of higher neutron and gamma-ray backgrounds that will damage equipment, specifically photodetectors, a critical component of science instruments. A technology that enables new instruments for discovery is the silicon photomultiplier, yet this photodetector will be damaged rapidly within these high-intensity radiation fields. The project is to design a solid-state photomultiplier that will be significantly more tolerant to the gamma-ray and neutron backgrounds by replacing the silicon with a different semiconductor material. The phase-I plan is to identify and grow a semiconductor epitaxial wafer for developing prototype Geiger photodiodes, which are the key elements within the solid-state photomultiplier. The diodes will be tested for their radiation tolerance with respect to equivalent silicon devices. Modeling work will be done to support the design of a photodetector in terms of optimizing the electrical and optical properties of the diodes for a high-speed, high-efficiency, radiation-tolerant solid-state photomultiplier. Along with physics instrumentation, the silicon photomultiplier is used for nuclear instruments in the medical fields and nuclear industry. The technology to be developed in the project will support applications where the detectors will be exposed to high radiation fields, such as those found in the nuclear industry, sciences, and space applications.