Speaker
Description
In low Earth orbit (LEO), cosmic ray interactions with spacecraft materials produce a complex secondary radiation field of neutrons, gamma rays, and charged particles, that significantly contributes to radiation exposure of astronauts. The radiation environment remains challenging to characterise due to the physical restrictions associated with measurements onboard spacecraft, and the mixed-field composition [1,2]. The need for compact, low-voltage radiation detectors is therefore critical for realistic dosimetry in these complex environments.
A 20 mm diameter plastic scintillator, optically coupled to a silicon photomultiplier, is being characterised through a combination of simulation and experimental measurements. The primary cosmic ray (PCR) field in LEO was simulated using the Space Environment, Effects, and Education System (SPENVIS) [3] to determine the radiation type and energy distribution of contributions from galactic and solar sources. The secondary radiation field, arising from PCR interactions with aluminium was estimated using SPENVIS for a range of thicknesses as an analogue to being situated within the ISS. While neutrons, protons and electrons are well represented, the secondary gamma-ray field from PCR interactions in aluminium shielding is not explicitly included. To overcome this limitation, the radiation transport code FLUKA [4] will be used to model secondary radiation production and estimate the detector response. The simulated detector response will be validated against experimental measurements made with low-energy (< 20 MeV) gamma ray and neutron sources at the n-lab [5] at the University of Cape Town.
The combined experimental-simulation approach is used to predict detector performance in the ISS environment for measuring the ambient radiation field and transient variations associated with space weather events [2]. Measurements are being planned at high altitude in the atmosphere and in LEO.
References
[1] L.H. Heilbronn et al., Life Sci. Space Res. 7 (2015) 90–99.
[2] C. Zeitlin et al., Life Sci. Space Res. 39 (2023) 76–85.
[3] D. Heynderickx et al., Space Weather 2 (2004) S10S03.
[4] G. Battistoni et al., Ann. Nucl. Energy 82 (2015) 10–18.
[5] T. Hutton, A. Buffler, Appl. Radiat. Isot. 206 (2024) 111196.
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