Development of scintillation neutron detectors using wavelength-shifting fiber (WLSF) technology at J-PARC MLF is briefly reviewed. The neutron-detecting head of this type detector comprises neutron-sensitive scintillator screens and WLSFs for light read out. The light collection using WLSFs enables us to design a detector with great flexibility. Detector specifications such as pixel size, spatial resolution, and neutron-sensitive area can be optimized to requirements in specific applications. We have intensively developed these detectors since 2005. A large number of detector modules have been produced and delivered to the neutron scattering instruments in the MLF. In this paper the design of SENJU detector is presented in detail together with recent development effort for detector technology alternative to helium-3 gas detectors.
A Flat-panel and Resistor type PMT (FRP) system which is a two-dimensional position-sensitive neutron detector has been developed. The FRP system is a replacement of the RPMT system which has been out of production. The FRP detector consists of a multi-anode PMT (MA-PMT), a resistor network board and an FRP amplifier, and provides similar signals to those of the RPMT detector. Therefore, the FRP system uses the same readout circuit as that of the RPMT system. There are two types of detectors. One is a FRP4 detector which consists of four MA-PMTs with detection area of 7.5 × 7.5 cm2. The position resolution by irradiation of neutron beam of about 0.5 mm diameter is 1.26 mm on the X axis and 1.61 mm on the Y axis. The other is a FRP1 which consists of one MA-PMT with detection area of 3.5 × 3.5 cm2. The position resolution by irradiation of neutron beam of about 0.5 mm diameter is 0.83 mm on the X axis and 0.89 mm on the Y axis.
Here we report new concept of neutron detector with Glass GEM and Boron convertor. Glass GEM is fabricated with photo-etchable glass process. The conductivity of the substrate is efficient to avoid charge up and is suitable for high-count-rate application. Glass is also an attractive material for robust and stable detector. The Glass GEM detector is tested at J-PARC BL16, and succeed in detecting neutron at high-count-rate and low gamma-ray sensitivity.
A glass capillary plate (CP) gas detector is a hole-type micro pattern gaseous detector (MPGD). A hole-type MPGD typically consists of a thin insulator sheet (0.05–2 mm thick) with a large number of small holes (0.01–1 mm diameter). We have successfully developed an optical imaging CP gas detector, which consists of a CP gas detector, a mirror, and a cooled CMOS camera system, for neutron imaging. Its performance was investigated using a thermal neutron beam at KUANS. Owing to the high imaging capability of the optical imaging CP gas detector, tracks of α-rays or 7Li produced by the interaction between neutrons and 10B were clearly observed. We report on the properties of the optical imaging CP gas detector as a neutron imager and describe the outlook for future developments on the basis of the results of Monte Carlo simulations.
A self-standing single-crystal CVD diamond was fabricated using a lift-off method. The reduction of charge trapping factors such as structural defects, point defects, and nitrogen impurities, was attempted using 0.2% of low-methane concentration growth and using a full metal seal chamber. A high-quality self-standing diamond with strong free-exciton recombination emission was obtained. Charge collection efficiencies were 100.1% for holes and 99.8% for electrons, provided that εdiamond = 13.1 eV and εSi = 3.62 eV. Energy resolutions were 0.38% for both holes and electrons. Finally, energy resolution of 0.78% for 14 MeV neutrons was achieved. Moreover, ToF measurement for DD neutrons of implosion experiment at Gekiko XII laser was succeeded.
The Energy-Resolved Neutron Imaging System RADEN, located at the J-PARC Materials and Life Science Experimental Facility, is the world’s first dedicated high-intensity, short-pulsed neutron imaging beam line. To carry out energy-resolved neutron imaging at RADEN, we use cutting-edge detector systems, recently developed in Japan, employing micro-pattern detectors or fast Li-glass scintillators coupled with high-speed, all-digital data acquisition systems. These counting-type detectors provide sub-μs time resolution, high neutron count rates, and event-by-event gamma rejection. The detectors available at RADEN offer a range of spatial resolutions from 0.25 to 3 mm and counting rates up to 8 Mcps. In the present paper, we show the performance of these detector systems as measured at RADEN and discuss ongoing development efforts aimed at improving spatial resolution and count rate performance.