Measurement of neutron and γ-ray intensity distributions with an optical fiber-scintillator detector

On the tip of an optical fiber, a very small amount of ZnS(Ag) scintillator mixed with neutron converter and adhesive paste was painted, which can be inserted into a narrow space and moved by a fiber-driving unit controlled with a personal computer. The presented method made it possible to measure neutron flux distributions in critical assemblies, research reactors or other neutron facilities with position resolution of less than 1 mm and in 10 min or so over a meter. As neutron converter, 6Li and 235U are good for thermal neutrons and 232Th is useful for fast neutrons. When a neutron converter is not used, the method can be applied to the measurement of γ-ray intensity distribution.