Radiation dosimetry for high LET particles in low Earth orbit

Abstract

Research indicates that the impact to human tissues from radiation exposure is strongly related to the LET (linear energy transfer) of the particles and particles with high LET ( ⩾ 5 KeV / μ m water) dominate the damage. High LET radiation in LEO (low Earth orbit) is composed mainly of galactic cosmic rays (GCR), solar energetic particles, particles trapped in the SAA (South Atlantic Anomaly), and albedo neutrons and protons scattered from the Earth's atmosphere. So far the active personal dosimeters are not available and the best passive personal dosimeters currently applied to the radiation assessment for astronauts are CR-39 detectors (for the high LET part) in combination with thermoluminescence detectors (TLDs) or optically stimulated luminescence detectors) (OSLDs) (for the low LET part). LET spectra for radiation in LEO were determined with CR-39. This paper introduces the operational principles for CR-39 detectors, describes the method of LET spectrum using CR-39 and presents the results measured with CR-39 and TEPC (tissue equivalent proportional counter) for space mission ISS-Expedition 2, STS-108, STS-112, ISS-7S, STS-114 and STS-121.