Image detection methods for 14·5-MeV neutrons: Techniques and applications

Abstract

Three methods for detecting images with neutrons produced by the ( d, T) reaction are considered. These are (1) the direct method, in which X-ray film with or without intensifying screens is exposed to the neutron beam, (2) the transfer method in which an autoradiograph of a neutron-activated foil is obtained and (3) the track-etch method, in which radiation damage tracks in polycarbonate and cellulose nitrate plastics are made visible. The latter two methods offer the advantage that they are insensitive to gamma rays. Sensitivities and contrast capabilities of each method are discussed. The best methods in each group, with the total fast-neutron exposure needed for a good quality image enclosed in parentheses, are scintillator-film detectors (5 × 10 7 n/cm 2) for the direct method, double foil copper screens (1·2 × 10 10 n/cm 2 for a 30-min, 3 half-life activation) for the transfer method, and a new cellulose nitrate plastic (2 × 10 10 n/cm 2) for the track-etch method. Applications of these image-detection methods to the study of the uniformity of neutron beams, to the detection of interfering gamma or X-radiation, to the location of irradiation samples in the neutron beam, and to the performance of radiography with fast neutrons are discussed.