Shielding verification in radiation space environment with biologically relevant dosimetry
Abstract
Astronauts are exposed to high-energy cosmic radiation, which may have harmful health effects. At the altitude of the International Space Station (ISS), the main radiation sources are Galactic Cosmic Rays (GCRs), Solar Particle Events (SPEs) and trapped protons of the Van Allen Belts. The radiation field mainly consists of protons, alpha particles and heavy ions with energies up to hundreds of GeV/u. The dose equivalent, H, is a quantity which expresses the probability that exposure to ionizing radiation will cause biological effects. It is obtained by multiplying the dose by the dose average quality factor, Q$ _{ave}$, of the radiation. Microdosimetry based on energy deposition measurements on a cellular level allows predict radiobiological efficiency of ionizing radiation and derive of a mixed radiation field typical of space radiation, without knowledge of energy or type of particles. This work presents experimental studies of response of silicon on insulator (SOI) microdosimeters with 3D sensitive volumes (SVs) to Galactic Cosmic Rays heavy ions typically encountered in space before and after a realistic multi-layers sample of the International Space Station Columbus module's shielding wall. Aluminum, Kevlar-Epoxy, Nextel layers were used to mimic the ISS wall during the experiment. The SOI microdosimeter was irradiated using 290 MeV/u $ ^{12}$C, 400 MeV/u $ ^{16}$O, 400 MeV/u $ ^{20}$Ne, 230 MeV/u, 490 MeV/u $ ^{28}$Si and 500 MeV/u $ ^{56}$Fe ions with and without the ISS walls at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. The dose equivalent H, and quality factor Qave behind various spacecraft shielding wall configurations and materials are presented. Particularly, we investigated carbon fibre, polyethylene, perspex with the same areal density of currently used aluminum for potential improvement of radiation shielding. The results show that depending on energy and type of ions, some ions could become more harmful once they reached the inside of the spacecraft due to the high LET and secondaries produced while propagating through the ISS wall and others could totally stop in the wall while still producing secondaries resulting a lower and dose equivalent. Detailed results for every configuration will be presented at the conference. This study confirms that the portable SOI microdosimeter is suitable for quantifying the quality of the radiation field in space in terms of Q$ _{ave}$, as well as evaluating the efficiency of shielding materials in terms of H. Results have been validated with Geant4 simulations, confirming the feasibility of using SOI microdosimeter for personal dosimetry of astronauts.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1867R