@misc{oai:repo.qst.go.jp:00064705,
 author = {Yajima, Kazuaki and Yasuda, Hiroshi and 矢島 千秋 and 保田 浩志},
 month = {Sep},
 note = {Measurements of cosmic-ray origin neutron energy spectra using a phoswich detector were performed at the various geographical latitudes in Japan: Wakkanai (45.4 N), Hirosaki (40.6 N), Chiba (35.6 N), Kagoshima (31.6 N) and Itoman (26.1 N). The cylindrical probe of the phoswich detector consists of a 12 cm diameter and a 12 cm long short-decay-time (3.5 s) liquid scintillator covered with 1.5-cm thick long-decay-time (285 s) plastic scintillator.  The analog signals from the phoswich detector were converted into digital pulse data by the custom-made high speed processing unit. Neutron signals from phoswich detector were separated from other particle signals by means of a pulse shape discrimination method based on the difference of the decay time between the liquid scintillator and the plastic scintillator. The FERDO-U code was used in the unfolding process. We adopted the Excel-based program for calculating atmospheric cosmic-ray spectrum (EXPACS) as the calculation program for the cosmic-ray origin neutron energy spectrum in this work. The calculation with EXPACS can reproduce well the previous cosmic-ray origin neutron energy spectra measured with multi-moderator spectrometer (Bonner Ball).
Measured neutron energy spectra for the energy range from 18 to 110 MeV obtained in Hirosaki measurement showed two peaks, one was at around 30 MeV and the other 80 MeV. The shape of the measured spectra did not agree with that of the calculated spectra. The fluence rate at 80 MeV for the measured spectra was about twice of that for the calculated spectra. On the other hand, the integrated fluence rate from 18 to 110 MeV for the measured spectra was about 20 percent less than that for the calculated spectra. As for the integrated fluence rate it may be said that the measured value is close to the calculated value. Preliminary results for Chiba and Itoman measurements showed similar features to Hirosaki measurement. We work on analysis of the data obtained in Wakkanai and Kagoshima measurement now. The next step is to examine whether or not the phoswich detector can catch the latitude dependence of the cosmic-ray origin neutron energy spectra., 12th Internationa Conference on Radiation Shielding and 17th Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society ( ICRS-12 & RPSD-2012)},
 title = {Measurements of cosmic-ray origin neutron energy spectra using a phoswich detector at the various geographical latitudes in Japan},
 year = {2012}
}