Design and characteristics of the JRR-3M thermal neutron radiography facility and its imaging systems

The JRR-3M thermal neutron radiography facility was constructed in the JRR-3M of the Japan Atomic Energy Research Institute in 1991 and has been used as a research facility for various kinds of research fields. The characteristics of the facility have been briefly reported and declared to be excellent in neutron flux and in collimator ratio. Additionally, the authors have measured the beam flatness and the scattered components and have compared these measured characteristics with the design values. The neutron source, the beam tube, and the radiography rooms are described in detail and their data are applied to the analyses of the characteristics. The description of the radiography rooms includes beam size definition tubes and beam shutters, which are the most important components in the room. Also described are the restrictions on the size and shape of the sample, the background dose rates, and equipment information. The high-performance of the facility enables advanced imaging techniques such as high spatial resolution imaging and high temporal resolution imaging. The high-resolution static neutron radiography system using a cooled charge-coupled device camera has the capability to take neutron radiography images with 72 μm of spatial resolution. The high frame rate neutron radiography system has the capability to image high-speed phenomena with 4500 frames/s of temporal resolution. Both neutron radiography systems are described in detail especially for key components such as fluorescent converters and cameras.