Measurements of Cosmic-Ray Neutron Energy Spectra from Thermal to 15 MeV with Bonner Ball Neutron Detector in Aircraft

Cosmic-ray neutron energy spectra from thermal to 15 MeV 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.