Resolution Study of Photographic Thermal Neutron Image Detectors

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Abstract
The high contrast resolving power of several photographic thermal neutron image detection methods has been experimentally determined. For the most part, the comparisons between the different imaging techniques were made after optimizing each technique for resolution capabilities. The resolution was studied by determining the minimum hole separation in an almost totally absorbing object which could be resolved by a number of observers on neutron radiographs made by each method. From the standpoint of resolution, the best methods employed thin gadolinium metal screens, compressed Li‐6F powder, and a thin B‐10 layer covered with a vapor deposited ZnS (Ag) phosphor in techniques in which the photographic film and screen were exposed together to the low gamma content, 1.05 Å monochromatic neutron beam. A transfer of an image carrying radioactive gold screen to film also yielded resolution values in the order of 0.001 in. Evidence is presented to explain many of the observed resolution comparisons on the basis of the average penetrating power of the photographically effective radiation emitted from the converter screen. A technique for measuring this property on a comparative basis is described.

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