Fast neutron spectrum measurement in high gamma fluxes using nuclear emulsions

Abstract

Measurement of fast neutron spectra with nuclear emulsions has been limited to applications where the ratio of gamma to fast neutron is low. Gamma radiation produces background fogging in the developed emulsion and, if excessive, this obscures the proton tracks. Previous workers have been limited to a total γ-dose of about 1 to 1·5 rad. By adding 4g/l of a de-fogging agent 1-phenyl-5-mercapto-tetrazole to the developing solution, we have been able to scan proton tracks in an emulsion subjected to 8 rad total γ-dose. Using this procedure the fast neutron spectrum within the core of the Universities Research Reactor has been measured with Ilford L-series nuclear emulsions.