Measurements of the neutron dose and energy spectrum on the International Space Station during expeditions ISS-16 to ISS-21

Abstract

As part of the international Matroshka-R and Radi-N experiments, bubble detectors have been used on board the ISS in order to characterise the neutron dose and the energy spectrum of neutrons. Experiments using bubble dosemeters inside a tissue-equivalent phantom were performed during the ISS-16, ISS-18 and ISS-19 expeditions. During the ISS-20 and ISS-21 missions, the bubble dosemeters were supplemented by a bubble-detector spectrometer, a set of six detectors that was used to determine the neutron energy spectrum at various locations inside the ISS. The temperature-compensated spectrometer set used is the first to be developed specifically for space applications and its development is described in this paper. Results of the dose measurements indicate that the dose received at two different depths inside the phantom is not significantly different, suggesting that bubble detectors worn by a person provide an accurate reading of the dose received inside the body. The energy spectra measured using the spectrometer are in good agreement with previous measurements and do not show a strong dependence on the precise location inside the station. To aid the understanding of the bubble-detector response to charged particles in the space environment, calculations have been performed using a Monte-Carlo code, together with data collected on the ISS. These calculations indicate that charged particles contribute <2% to the bubble count on the ISS, and can therefore be considered as negligible for bubble-detector measurements in space.

Bubble-Detector Measurements of Neutron Radiation in the International Space Station: Iss-34 to Iss-37

“…The bubble-detector data from 2009 to 2012 were compared with data from the ISS tissue-equivalent proportional counter (TEPC) and the Russian DB-8 dosemeters, which were co-located with the bubble detectors in the Russian segment at the time of the measurements. This inter-comparison agreed with previous empirical measurements (7,9) and theoretical calculations (10) , suggesting that neutrons account for 30 % of the total dose equivalent in LEO. The 2009-12 data were also correlated with quantities that might be expected to influence the measurements, including the ISS altitude and solar activity.…”

“…Some of the experiments were conducted using a hydrogenous radiation shield and a reduction in neutron dose was determined due to the shielding. This result was similar to that from an earlier bubble-detector experiment (7) in the JEM using a different water shield. The bubble-detector data from 2009 to 2012 were compared with data from the ISS tissue-equivalent proportional counter (TEPC) and the Russian DB-8 dosemeters, which were co-located with the bubble detectors in the Russian segment at the time of the measurements.…”

“…The detectors used in this work were calibrated at the Bubble Technology Industries facility using established procedures (7) developed for commercial bubble detectors. The detector sensitivity was calibrated using an AmBe source with a neutron emission rate of 1.13`Â 10 7 s 21 and a conversion coefficient of 4.11`Â 10 24 mSv cm 2 [according to the International Commission on Radiation Units and Measurements (ICRU)…”

“…Experiments started in 2006 as part of the international Matroshka-R experiment based in the Russian segment of the ISS. Several measurements, each approximately a week long, were performed in the various Russian modules during the ISS-13 to ISS-19 missions (6,7) . This included experiments with the Matroshka-R tissueequivalent spherical phantom, which demonstrated that the dose received inside the phantom is lower than that at the phantom surface.…”

“…The Matroshka-R experiments with bubble detectors continued during the ISS-20 and ISS-21 missions in 2009 (7) . At the same time, the Radi-N experiment commenced in the US Orbital Segment (USOS) of the ISS.…”