High-position-resolution neutron imaging detector with crossed wavelength shifting fiber read-out using two ZnS/6LiF scintillator sheets

High-intensity pulsed neutron sources have made a great deal of progress in Japan (J-PARC project), the United States (SNS project), and the United Kingdom (ISIS-II project). The specifications required for neutron imaging detectors used at these facilities are a high-position resolution, a high-detection efficiency, a high counting rate, a high n/γ ratio, etc. Especially the detectors which exhibit a high-position resolution and high detection efficiency are required for the crystallography diffractometers. It is also essential for these detectors to be compact and to have the least dead-detection area for a large solid-angle coverage. We have developed a compact high-position-resolution neutron-imaging detector with wavelength shifting (WLS) fibers using two scintillator sheets. The developed detector structure ensures compactness and easy assembly of these types of detectors. It was confirmed that the neutron imaging detector using WLS fibers with a size of 0.5×0.5 mm exhibited a position resolution of less than 0.8 mm. The detection efficiency for thermal neutrons was improved 55% by using the two scintillator sheets from 29% by the single sheet.