Particle - Identified Spectroscopy with Phoswich Detector in High-Energy Mixed Radiation Field

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Neutron spectra have scarcely been measured on board a spacecraft or an aircraft, because the neutron measurement requires a discrimination between neutron and charged-particle events. In this viewpoint, we have developed a new phoswich detector consisting of an NE213 liquid scintillator (133mm diam. X 133mm long) surrounded by an NE115 plastic scintillator (10mm thickness). The light induced by charged particles in the NE115 scintillator has a long characteristic decay time constant of 225nsec, whereas the light by recoil protons from neutrons in the NE213 has the time constant of 30nsec. These differences in the light-decay time constant make it possible to separate pulses of the different particle species. This detector can measure the neutron spectrum up to about 130MeV by discriminating between neutron and charged-particle events in a mixed field in space.A mixed field of neutrons and charged particles were produced by bombarding 70MeV protons on a 2mm thick Be target at the NIRS … More (National Institute of Radiological Sciences) cyclotron facility and by bombarding 100MeV/n carbon ions on stopping length carbon or aluminium target at the HIMAC (Heavy Ion Medical Accelerator in Chiba) in the NIRS. The detector was placed at 3〜5m downstream from the target at 0〜45deg. To the beam axis. It was found that this phoswich detector was able to discriminate neutron and gamma-ray events from incident charged-particle events.The response functions of the phoswich detector to neutrons were measured with neutrons from the Be+C target bombarded by 135MeV protons from the RIKEN (Institute of Physical and Chemical Research) ring cyclotron. The measured response functions for neutrons were compared with Monte Carlo calculations, SCINFUL code. From these experimental and calculated response functions, the response matrices were completed for neutrons up to 130MeV. By unfolding the experimental spectra with the FERDOU code, the gamma-ray and neutron spectra in a mixed field of neutrons and charged particles at NIRS cyclotron were obtained. Less