MEASUREMENTS OF DT AND DD NEUTRON YIELDS BY NEUTRON-ACTIVATION ON THE TOKAMAK FUSION TEST REACTOR

A variety of elemental foils have been activated by neutron fluence from the Tokamak Fusion Test Reactor under conditions with the DT neutron yield per shot ranging from 1012 to over 1018. Linear response over this large dynamic range is obtained by reducing the mass of the foils and increasing the cooling time, all while accepting greatly improved counting statistics. Effects on background gamma-ray lines from foil-capsule-material contaminants, and the resulting lower limits on activation foil mass, have been determined. DT neutron yields from dosimetry standard reactions on aluminum, chromium, iron, nickel, zirconium, and indium are in agreement within the ±9% (one-sigma) accuracy of the measurements; also agreeing are yields from silicon foils using the ACTL library cross section, while the ENDF/B-V library has too low a cross section. Use of the 115In(n,n′) 115mIn reaction (0.42 times as sensitive to DT neutrons as DD neutrons) in conjunction with pure-DT reactions allows a determination of the DT/(DD+DT) ratio in trace tritium or low-power tritium beam experiments. © 1995 American Institute of Physics.