Increasing neutron yield and minimizing copper sputter by varying the diameters of a DPF hollow anode*

Experiments were performed to maximize neutron yield from a dense plasma focus (DPF) and characterize the amount of copper sputtered from the surface of an anode by varying the diameter of the anode's on-axis hollow. These experiments were performed at Lawrence Livermore National Lab on a kJ-class DPF. All of the anodes with a hollow produced greater yields per discharge than anodes without a hollow. The largest average yield produced (9.1+/-0.4x10⁶ neutrons per discharge) was 6.2 times higher than the average yield with no hollow, and the data suggest an optimal hollow diameter. Qualitative differences in surface damage were seen on each anode and quantitative measurements were performed by measuring the copper sputtered onto on-axis quartz targets for three newly machined anodes of varying hollow diameters.