Abstract
The neutron ambient dose equivalent induced by galactic cosmic ray-like (1 GeV/u 56Fe) radiation stopped in a thick aluminum shield was measured at different angles with GSI neutron ball, the standard TLD (thermoluminescent dosimeters) based neutron dosimeter for area monitoring at the GSI facility. In order to measure reliably at large angles, a modified version of the GSI ball, including a set of three more sensitive TLD600H/700H cards, instead of one standard TLD600/700, cards was used. The modified GSI balls were calibrated in neutron reference fields of 241Am-Be(alpha,n) available at the Physikalisch-Technische Bundesanstalt (PTB). The neutron ambient dose equivalent was measured at 5 different angles (15, 40, 90, 115 and 130 degree) with respect to the beam direction and compared to the calculated detector response and ambient neutron dose equivalent results from FLUKA simulations. The dosimeter readings were corrected for signal contributions coming from secondary charged particles. An agreement within 15 % was found between the measured and calculated GSI ball response and an agreement within 30 % was found between experiments and calculated neutron dose equivalents.
Highlights
Long-term manned space missions to Mars and the construction of a permanent Moon base with a large crew both represent two of the most challenging new frontiers of human space flight exploration
Results for the neutron ambient dose equivalent measured by the thermoluminescence dosimeters (TLDs) at the different positions normalized per primary particle are reported in Table 1 together with the distances between the detector and the target center
The mixed radiation field, generated by 1 GeV/u 56Fe ions fully stopped in a thick aluminum target, has been characterized in terms of neutron ambient dose equivalent with GSI ball neutron dosimeters, the standard neutron dosimeter for area monitoring at the GSI accelerator facility
Summary
Long-term manned space missions to Mars and the construction of a permanent Moon base with a large crew both represent two of the most challenging new frontiers of human space flight exploration. TLD-Based Secondary Neutron Field Characterization limited by the large uncertainties of the basic physical and radiobiological models and the limited amount of experimental data for the reaction and production cross-sections of particles from galactical cosmic radiation (GCR) [6]. When studying shielding approaches for planetary habitats, the exploitation of in-situ materials to build very thick shielding represents one of the most realistic strategies with which to maximize shielding efficiency while limiting costs. In this context, the lack of experimental data on neutron and light ion production after thick shielding material by highly energetic ion radiation represents one of these significant knowledge gaps. Secondary neutrons—abundantly produced through all phases of a nuclear fragmentation process—represent a severe threat for the astronauts’ health due to their high penetration length and their increased biological effectiveness
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