Neutron dosimetry inside the international space station

This article presents descriptions of instruments and measurement results of neutron dosimetry for astronaut safety inside the International Space Station (ISS). Most neutrons inside the ISS are the secondary particles, and, especially for E > 100 keV, are one of the major contributors to the radiation dose received by astronauts because of their high radiation quality factor. The Bonner Ball Neutron Detector (BBND) experiment was conducted onboard the US Laboratory Module of the ISS as part of the Human Research Facility project of NASA over an eight-month period in 2001, corresponding to the maximum period of solar-activity variation, in order to evaluate the neutron radiation environment in the energy range from thermal up to 15 MeV inside the ISS. The BBND experiment is the first active measurement of neutrons inside the ISS, providing new knowledge about astronaut safety concerning the radiation environment as well as important inputs for further radiation environment model calculations. However, the BBND experiment can be considered as only half of the necessary evaluation of the neutron radiation environment inside the ISS since neutrons of 10 MeV < E < several hundreds MeV are considered to make a comparable contribution to the radiation dose to that in the BBND measurement energy range. A scintillation fiber neutron detector with a sensitive energy range higher than 10 MeV has been developed, which is complementary to the BBND instrument. Wide-energy range measurements of neutrons by these detectors shall permit evaluation of total contribution from neutrons to the radiation dose received by astronauts.