Linus S. Allen

Determination of the thermal neutron absorption cross section of 1-liter rock samples by a pulsed source technique

Abstract A method is presented for measuring the thermal neutron absorption cross section of geological rock samples. Neutrons from a pulsed 150 kV ion accelerator are thermalized in a 1 1 sample surrounded by a water reflector. The water is in a cylinder concentric with the sample, and it aids in reducing neutron leakage from the system. A He-3 detector inserted in the sample monitors the thermal neutron die-away. The thermal neutron cross section is calculated from the die-away rate using diffusion theory in a fundamental mode analysis for the concentric cylinder geometry of the sample and water reflector.