Copper activation deuterium-tritium neutron yield measurements at the National Ignition Facility

A DT neutron yield diagnostic based on the reactions, 63Cu(n,2n)62Cu(β+) and 65Cu(n,2n) 64 Cu(β+), has been fielded at the National Ignition Facility (NIF). The induced copper activity is measured using a NaI γ-γ coincidence system. Uncertainties in the 14-MeV DT yield measurements are on the order of 7% to 8%. In addition to measuring yield, the ratio of activities induced in two, well-separated copper samples are used to measure the relative anisotropy of the fuel ρR to uncertainties as low as 5%.