Evaluation of High-frame-rate Camera with Digital Accumulation System Combined with Neutron Color Image Intensifier for Energy Resolved Neutron Imaging

Abstract

The energy-resolved neutron imaging system RADEN, located at beamline BL22 of the J-PARC Materials and Life Science Experimental Facility, is the world's first dedicated high-intensity pulsed neutron imaging instrument. The neutron-energy-dependent imaging technique is based on energy analysis of neutrons using a time-of-flight method; this technique allows direct in situ imaging of the macroscopic distribution of the microscopic properties of materials, including the crystallographic structure and internal strain, nuclide-specific density, and magnetic fields. For these applications, a new type of equipment, a camera detector, has been developed that consists of a neutron color image intensifier, a photon image intensifier, and a high-frame-rate camera. The camera detector has three operating modes, which are sets of a frame rate (time resolution) and a pixel number (spatial resolution), to provide an appropriate set for each application. The performance of the camera detector was measured at RADEN, revealing a good spatial resolution of 0.22 mm at a modulation transfer function of 3% and an imaging area of 100 × 100 mm 2. Using the newly configured camera system, a neutron counting technique for calculating the center-of-gravity of bright spots originating from interaction of neutrons and a scintillator was evaluated, and the improvement in the spatial resolution was confirmed.