The Investigation of Neutron Kinetics and Cross Sections in Fast Nonmoderating Assemblies by the Nanosecond Pulsed Neutron Source Technique

Abstract

Nanosecond bursts of monoenergetic neutrons in the range 0.8–1.6 Mev are injected into non-moderating assemblies of bismuth, lead, and natural uranium. The flux in these assmblies is observed to decay exponentially with characteristic nanosecond time constants in good agreement with one velocity transport theory, and the known inelastic scattering and absorption cross sections.These experiments serve as a check on the validity of the assumptions of transport theory. The technique also serves as a method for measuring macroscopic inelastic and absorption cross sections directly, without the necessity of making the corrections required in other methods e.g., for double scattering and for the angular distribution.Nanosecond bursts of monoenergetic neutrons in the range 0.8–1.6 Mev are injected into non-moderating assemblies of bismuth, lead, and natural uranium. The flux in these assmblies is observed to decay exponentially with characteristic nanosecond time constants in good agree-ment with one velocity transport theory, and the known inelastic scattering and absorption cross sections.These experiments serve as a check on the validity of the assumptions of transport theory. The technique also serves as a method for measuring macroscopic inelastic and absorption cross sections directly, without the necessity of making the corrections required in other methods e.g., for double scattering and for the angular distribution.