Name of research institute or organization:
National Institute of Radiological Sciences

Title of project:
Continuous monitoring of cosmic-ray induced neutrons at the summit of Mt. Fuji
 

Project leader and team:
Kazuaki YAJIMA

Project description:

Cosmic-ray induced neutrons (cosmic neutrons) are the main contributor to cosmic radiation exposure at aviation altitudes. We have monitored cosmic neutrons with the radiation monitoring system using a long-distance wireless LAN constructed in the Mt. Fuji Weather Station from August 22, 2013 to July 7, 2014. An extended-energy neutron rem counter (WENDI-II) was used for the cosmic neutron measurement.
  In the measurement period, the rem counter count rate in count per hour (cph) changed with approximately 20% of variance between 80 ? 150 cph. Negative correlation is seen between the neutron count rate and the atmospheric pressure clearly. This is because the absorption in the atmosphere of cosmic neutrons increases as the upward atmosphere thickens. No correlation was seen between the neutron count rate and the change in a day.