Development of Energy-Resolved Neutron Imaging Detectors at RADEN

Abstract

Energy-resolved neutron imaging at a pulsed source utilizes the energy-dependent neutron transmission measured via time-of-flight to extract quantitative information about the internal microstructure of an object. At the RADEN instrument at J-PARC in Japan, we use cutting-edge detectors employing micro-pattern detectors or fast Li-glass scintillators and fast, all-digital data acquisition to perform such measurements, while continuing their development toward better utilization of the intense neutron source. In particular, for the Micro-Pixel Chamber based Neutron Imaging Detector (µNID), a micro-pattern detector with a 400 µm pitch and employing 3 He for neutron conversion, we have successfully improved the spatial resolution from 200 to 100 µm, increased the detection efficiency from 18 to 26% for thermal neutrons, and increased the maximum count rate from 0.4 to 1 Mcps. We are also testing a new readout element with a 215 µm pitch for further improved spatial resolution, and a µNID with boron-based neutron converter for increased rate performance.

Experimental validation of the brightness distribution on the surfaces of coupled and decoupled moderators composed of 99.8% parahydrogen at the J-PARC pulsed spallation neutron source

“…An effective count rate of 1.8×10 5 cps for the nGEM detector and was reported in Ref. [48]. The count rate in the experiments is about 10 4 cps at most and is much lower than the effective count rate.…”

Development of Event-Type Neutron Imaging Detectors at the Energy-Resolved Neutron Imaging System RADEN at J-PARC

“…Over the last several years, we have completely rewritten the data processing software in order to optimize the performance from the ground up, including optimization of the position calculation and implementation of a new clustering algorithm for an improved spatial resolution of 0.1 mm and an increased rate performance to more than 1 Mcps, respectively, as described in Ref. [9].…”

“…The performance of these detectors, as measured at RADEN, has recently been presented in Ref. [9], and the results are summarized in Table 1. We are continually working to improve our event-type neutron imaging detectors for better spatial resolution and shorter measurement times and, as a user facility, to improve the ease-ofuse of their control and analysis software.…”

Neutron Imaging at Compact Accelerator-Driven Neutron Sources in Japan

“…However, it was also designed to have capability of high L/D measurement that cannot be done at other imaging facilities in Japan, since the maximum L/D value was 175 in Japan. Various types of neutron detectors are available [16], such as an n-GEM (boron-coated Gas Electron Multiplier) detector [17], a µ-NID (Micro-pixel chamber-based Neutron Imaging Detector) [18], a pixel-type detector [19], and neutron color imaging intensifiers [20]. Spatial resolutions are 800, few 100 s, 2000~3000, and few 100 µm, respectively.…”