Characterization of the YAYOI fast neutron radiography field

Fast Neutron Radiography (FNR) has been studied with the use of the fast neutron source reactor YAYOI of the University of Tokyo. Three kinds of imaging techniques have been applied to the FNR. A CR39 nuclear track detector called the track-etch method has been successfully used in the first FNR experiments at YAYOI. The etched out images on the CR39 sheet usually have a low optical density, and took about 24 hours to get images. In order to perform an imaging technique with a high resolving power and high contrast, a thin type of luminescent converter and X-ray film method (film method) has been developed for the FNR. The converter is made of a mixture of PMMA and ZnS(Ag). the thickness of which is 40 μm. The system could observe a gap of 100 μm, and took about 3 hours to get results. To make the required imaging time shorter, a television system of fast neutron radiography (FNR-TV) was proposed. In the system, the same technique as a current thermal neutron television system was applied while using a different luminescent converter. The prototype converter was made of a mixture of polypropylene resin and ZnS(Ag). od of determining L and D was proposed in this paper. Experimental result of L agreed with the geometric dimension of L, while the value of D will be discussed in another paper.