Fast Neutron Dosimeter for the Space Environment

Secondary neutrons make a significant contribution to the total absorbed dose received by space crews during long duration space missions However, only a limited number of measurements of the dose contribution from secondary neutrons have been made. In part this is due to an inability to easily discriminate between the fraction of dose which results from secondary neutrons and that which results from exposure to energetic charged particles. The energy of the secondary neutrons range from 1 to >100 MeV. Scintillation materials provide the optimum volume to payload performance, but their use has been limited by the need for PMTs. A compact, lightweight, low-voltage, sensitive photodetector, such as CMOS SSPMs are an ideal candidate for this application. In this work, we propose to develop a compact, lightweight, energy-efficient dosimeter for secondary neutrons from space radiation using state-of-the-art scintillation materials with a charged particle shield coupled to a high-gain, solid-state photomultiplier (SSPM), which is a high-density array of Geiger photodiodes, fabricated with CMOS (complementary metal-oxide-semiconductor) technology. Such a dosimeter would overcome many of the limitations in the current generation of neutron dosimeters and meet the dosimetry needs for future human-space-exploration missions to the moon and Mars.