Development of Cosmic Radiation and Energetic Particle Analyzing System: CREPAS

Information on the accurate spectrum of energetic cosmic-ray particles, particularly neutrons and protons, are important for radiological protection of aircraft crew. However, verification of cosmic radiation doses in aircraft is still difficult because detector signals attributing to different radiation components are mixed and hardly separated by means of a conventional, transportable radiation instrument. We have thus developed a new monitoring system “CREPAS” composed of a phoswich-type scintillation detector coupled with a high-speed data acquisition unit which can measure the waveform of 0 to 5 V signals from -20 to 400ns with 2ns intervals; the waveform data of 12-bit dynamic range are transferred to a personal computer via USB2.0 interface. The signal waveforms are analyzed on site in real time for discrimination of different radiation components such as neutrons, protons, muons/electrons and gamma rays. In order to examine its feasibility, CREPAS was exposed to accelerator beams and then used for cosmic radiation measurements at the summit of a high mountain and in a chartered jet aircraft. It was verified that this system can successfully measure cosmic-ray energetic neutrons (>10MeV) separately from other components. Determination of the precise energy spectra of neutrons and other components calls for further investigation.