Pulsed-neutron imaging is attractive technique in the research fields of energy-resolved neutron radiography and RANS (RIKEN) and RADEN (J-PARC/JAEA) are small and large accelerator-driven pulsed-neutron facilities for its imaging, respectively. To overcome the insuficient spatial resolution of the conunting type imaging detectors like µNID, nGEM and pixelated detectors, camera detectors combined with a neutron color image intensifier were investigated. At RANS center-of-gravity technique was applied to spots image obtained by a CCD camera and the technique was confirmed to be effective for improving spatial resolution. At RADEN a high-framerate CMOS camera was used and super resolution technique was applied and it was recognized that the spatial resolution was futhermore improved.
K: Image processing; Neutron radiography; Data processing methods; Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs etc) 1Corresponding author.
High-frame-rate camera detectors have been developed for time-resolved neutron imaging. In these detectors, image intensifiers (IIs) are used to amplify scintillation light, which deteriorates spatial resolution. Center-of-gravity and super-resolution processing were investigated using two high-frame-rate cameras and a simulated pulsed bright spot generating device made by an LED and an optical fiber 250 µm in diameter for improving the spatial resolution. These imaging systems were constructed for RADEN of J-PARC MLF and RANS of RIKEN. The results of the experiments showed that center-of-gravity and super-resolution processing were effective methods to improve the spatial resolution of these camera detectors.
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.
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