Cosmic-ray neutron energy spectra from thermal to 15MeV were measured with a multimoderator spectrometer known as the Bonner Ball Neutron Detector (BBND) at aviation altitude (9?11 km). Four flights were carried out around Nagoya Airport in Japan. The measured data were unfolded using the maximum entropy deconvolution code MAXED, and the derived spectra agreed with the calculated results using the PHITS-based analytical radiation model in the atmosphere (PARMA). The results of the in-flight measurement verified the accuracy of model calculation in regard to the neutrons within a certain energy range.
Research Containing: Bonner Ball
Evaluation of the neutron radiation environment inside the International Space Station based on the Bonner Ball Neutron Detector experiment
The Bonner Ball Neutron Detector (BBND) experiment was conducted onboard the US Laboratory Module of the International Space Station (ISS) as part of the Human Research Facility project of NASA in order to evaluate the neutron radiation environment in the energy range from thermal up to 15 MeV inside the ISS. The BBND experiment was carried out over an eight-month period from 23 March through 14 November 2001, corresponding to the maximum period of solar-activity variation. The neutron differential-energy spectra are compared with the model neutron spectrum predicted for the inside of the ISS, and are found to be in good agreement for E > 10 keV . In contrast, the ISS model spectrum has lower flux for E < 10 keV , which is likely due to the difference in the shielding environment. The neutron dose equivalent rates are 69 and 88 μ Sv / day for the two locations inside the US Laboratory Module, representing a 30% increase due to the difference in the localized shielding environment inside the same pressurized module. The influence of the ISS altitude variation is estimated for the neutron dose equivalent rate to increase by a factor of 2 over the ISS altitude variation of 300–500 km. The increase in the cumulative neutron dose equivalent due to the most significant solar event during the BBND experiment is 0.15 mSv, which contributes less than 1% to the annual neutron dose equivalent estimated from the BBND experiment.