Registration of fission-fragment tracks in several substances and their use in neutron detection

Abstract

In a number of substances energetic, heavy charged particles leave trails of radiation-damaged material which can be selectively attacked by chemical reagents to produce tracks visible in an optical microscope. This paper is a comparative study of the density and length distribution of such tracks produced by uranium fission fragments in several micaceous minerals, Makrofol (a polycarbonate polymer) and glass. By comparing the track densities with those measured in nuclear emulsions it is concluded that fission fragments are registered with 100 per cent efficiency in the micaceous minerals and in the Makrofol, but only with 40 per cent efficiency in the variety of glass that was studied. The results are shown to be consistent with the hypothesis that the average rate of energy loss of the charged particle determines the ability to form etched tracks. It has previously been pointed out that mica in combination with a fissile cover material has some signal advantages as a neutron detector. Several aspects of this application, including the measurement of track yields from thick uranium source, are discussed.