Targeted Nuclear Spallation from Moderator Block Design for a Ground-Based Space Radiation Analog

Abstract

Current radiobiology studies on the effects of galactic cosmic ray radiation utilize mono-energetic beams, where the projected dose for an exploration mission is given using highly-acute exposures. This methodology does not replicate the multi-ion species and energies found in the space radiation environment, nor does it reflect the low dose-rate found in interplanetary space. In radiation biology studies as well as in the assessment of health risk to astronaut crews, the differences in the biological effectiveness of different ions is primarily attributed to differences in the linear energy transfer (LET) of the radiation spectrum. Here we show that the LET spectrum of the intravehicular environment of spaceflight vehicles can be simulated with a single particle, mono-energetic ion beam accelerated at target blocks constructed of one or more materials. The LET spectrum of the emerging field can then be moderated by the amount of mass or length of material the primary and secondary nuclei travels, thus preferentially producing specific nuclear spallation and fragmentation processes and allowing for a continuous generation of ionizing radiation that mimics the space radiation environment. This approach could allow more accurate simulation of not only intravehicular spaceflight conditions, but also could be used to simulate the external galactic cosmic ray field, planetary surface spectrum (e.g., Mars or Moon), and the local radiation environment of orbiting satellites, providing a much-needed ground-based space radiation analog for future experimentation.