Thermal Neutron Absorption Cross Sections by the Pulsed Source Method

Abstract

AbstractThe thermal neutron absorption cross sections of twenty-one naturally occurring elements and B10 have been determined by comparing the time dependence of the neutron flux in water with the time dependence of the neutron flux in a water solution of the sample with the same geometric buckling. After making some small corrections arising largely from the change in the number of hydrogen atoms per cm3 in the solution, the decay constant of the ratio curve gives the macroscopic absorption cross section averaged over the neutron flux spectrum. For a 1/υ cross section the 2200 m/sec cross section can be directly computed. For non-1/υ cross sections the effective 2200 m/sec cross section is obtained. Notes* This work supported by the U. S. Atomic Energy Commission.