Contrast enhancement in neutron radiography using a gaseous penetrant

The absorption cross section of He3 is so great that even a few millimetres of gas at moderate pressures produce a significant change in the transmission of thermal and cold neutrons. This provides the possibility of a novel method for the detection of small leakage paths by neutron radiography. The paper first outlines the standard techniques for contrast enhancement and then illustrates the use of He3 with an account of an actual examination of electric bridge wire squibs, with some comment on sensitivity and cost. (Auth.)