Computational Approaches for Developing Active Radiation Dosimeters for Space Applications Based on New Paradigms for Risk Assessment

NASA has proposed new models for radiological risk assessment with significant revisions that are based on new epidemiological data and radiation biology results. Extensive computational approaches were used to develop new risk cross sections and the extension of these into recommendations for risk assessment during space missions1,2. This has been translated into revised specifications of quality factors in terms of track structure concepts that extend beyond LET alone and will require identification of charge, Z, and velocity, b, of the incident radiations. New paradigms for assessing REID for space radiation place demands on radiation monitoring procedures that are not satisfied by existing dosimetry systems or particle spectrometers. The objectives of this research are to exploit state-of-the-art computational capabilities to investigate how radiation dosimeters would respond to the incident radiations and what information needs to be extracted from the collected data to properly estimate dose and quality factors. It is essential to understand specific limitations of detector systems and what compromises need to be implemented before making and testing new devices. These priorities have been identified in the NASA Space Technology Roadmap;TA06-Human Health, Life Support and Habitation Systems; 2.5 Radiation: Radiation Monitoring “...established technologies are not sensitive to the full range of radiation that will be encountered beyond Earth orbit, nor do they give details about thetypes of particles contributing to the indicated dose. This is important because the most recent assessment of known radiation exposure for astronauts would limit them to approximately 90 days of exposure during missions outside of Earth orbit."
This Final report will provide a summary of the following Tasks that were emphasized during the grant period:
Task 1:Radiation Quality Factors for GCR particles encountered during manned missions in space.
Task2:The implications of multiple fragments in temporal coincidence when measuring the LET distributions of incident particles and spatial segmentation(i.e. pixilation) required for mitigation of clustered secondary particles.
Task3:The use of neural networks and statistical training of algorithms to extract the charge distribution, (LET, Z)of GCR particles from measurements of(LET)alone.
Task4:Methods to compute the yield of particle telescopes from random trajectories of incident particles.
Task5:A Method to obtain microdosimetric quantities without pulse height spectral analysis
Task 6:Computations of the yield and energy spectra of neutrons generated by GCR particles incident upon shielding materials.
Task 7:Computations of the yield and energy spectra of albedo neutrons emerging from regolith serving as the base for habitats in space.