Considerations and designs for a space-compatible, DPA-SSPM based space radiation monitor

Modern space electronics used in satellites are vulnerable to performance degradations and even system failure due to exposure to highly energized charged particles, such as electrons and protons originating from solar particle events, galactic cosmic rays, and trapped particles in the Van Allen Belts. The compact, radiation hard, detector system reported here distinguishes between electron events and proton events and provides the dose for both types of radiation on an event-by-event basis. This information enables an accurate estimate of component lifetimes and the damage effects in electronics resulting from total ionizing dose (TID), displacement damage dose (DDD), and single event upsets (SEU). The detector components consist of a space-compatible scintillation material, crystalline Diphenylanthracene (DPA), coupled to a Solid-State Photomultiplier (SSPM) to detect and discriminate electrons and protons based on pulse shape discrimination (PSD) techniques. The results presented here demonstrate further characterization of the detector´s critical components including PSD capabilities for DPA coupled to RMD´s 2^nd generation SSPMs. The sensor characterization results show that proton events with energies below ~400 MeV can be distinguished from electron events with energies below ~200 MeV. The low energy threshold for the sensor is 240 keV at room temperature. The sensor is tested with a ²⁴¹AmBe source, where the electron dose, from gamma rays, is 0.19 mGy, the proton dose (from neutron recoils) is 0.70 mGy, compared to the measured dose of 0.16 mSv from a Victoreen 451 survey meter. Additionally, this paper describes the dose calculation method, assumptions, and the FPGA-based readout system that has been designed to process the DPA-SSPM detector output for identification of electron-proton events.