Abstract
The opportunity of exposure to high-energy radiation up to GeV is increasing as at particle accelerators and high-altitude flights. Large uncertainties are accompanied to the biological effects of such energetic particles and to be further investigated. The high-energy transports are still difficult to describe precisely and thus verification by measurement using a well characterized instrument is indispensable for reliable dosimetry. However, no reference calibration field has been established for the high energy range. We thus propose to use a facility at the summit of Mt. Fuji (3,776m in altitude; N 35.36, E138.73), the highest place in Japan, for characterization of radiation instruments that are possibly used in high-energy radiation fields. For demonstration of the effectiveness, two moderator-type neutron monitors (NCN1 and WENDI-II) having different energy response functions were employed for cosmic-ray neutron measurements in the summer of 2009. In comparison with numerically simulated values, it was found that the extended energy neutron monitor (WENDI-II) has a good property suitable to measurement of the cosmic-ray neutrons with the broad range of energy. The unexpected response of NCN1 is to be investigated in ongoing studies.
