DPA-Based Fast Neutron Dosimeter for the Space Environment

The space environment is inherently complicated with multiple sources of radiation, and within a spacecraft, these radiation fields are further complicated by the production of secondary particles (i.e., γ, e±, n, π±, π⁰), where the generation of neutrons represent a significant contribution to the dose received by astronauts. The signals in most detectors resulting from neutron interactions are difficult to discriminate from other types of interactions such as the incident energetic protons and gamma rays, making it difficult to provide accurate dose equivalent information. The results presented here demonstrate the capability of Diphenylanthracene (DPA) scintillation materials to detect and discriminate fast neutrons from gamma rays using pulse shape discrimination (PSD) techniques. The new scintillation sensors generate amplitude and emission-time signatures that provide information regarding the neutron dose and linear energy transfer (LET). This information can then be used to determine appropriate quality factors and the dose equivalent or biological effect. Considerations for a DPA based dosimeter design will be presented along with optimization of the detector signal processing steps for discriminating neutrons from gamma rays. The emission time and amplitude signatures from a new scintillation material, crystalline DPA, are characterized for proton, neutron, and electron (from gamma-ray irradiation) irradiation. An estimation of Birk´s parameters for DPA, which is necessary to describe the light yield as a function of LET, is presented.