Counting-type neutron imaging detectors of the energy-resolved neutron imaging system RADEN at the J-PARC/MLF

摘要

The recently commissioned Energy-Resolved Neutron Imaging System, RADEN, located at the J-PARC Materials and Life Science Experimental Facility (MLF), is the world's first dedicated high-intensity, pulsed neutron imaging instrument. In addition to conventional radiography and tomography, the wide bandwidth and accurate measurement of neutron energy by time-of-flight is utilized to perform energy-resolved neutron imaging. Such techniques allow direct imaging of the macroscopic distribution of microscopic properties of materials in situ, including crystallographic structure and internal strain, nuclide-specific density and temperature distributions, and internal/external magnetic fields. To carry out such measurements in the high-rate, high-background environment at RADEN, we use cutting-edge detector systems, recently developed in Japan, employing micro-pattern detectors or fast Li-glass scintillators with high-speed, Field Programmable Gate Array-based data acquisition. These counting-type detectors offer sub-μs time resolution, high neutron count rates, and event-by-event gamma rejection. The available detectors offer a range of spatial resolutions from 0.3 to 3 mm and counting rates from 0.6 to 8 Mcps. In the present paper, we show the performance of these detectors as measured at RADEN. We also consider planned improvements to the detector systems that will allow us to achieve finer spatial resolutions by several factors and order-of-magnitude higher count rates.