Dynamics of a microscale dense plasma focus

Abstract

Experimental results are presented for a sub-millimeter dense plasma focus (DPF). Reducing the DPF from cm to µm sizes allows for unique applications such as portable neutron based detectors. With smaller size efficiency is expected to increase, but total neutron emission will be lower. Challenges are maintaining the various scaling parameters. Breakdown scaling suggests higher pressure operation though there are limitations at high pressure in confinement due to increased collisions. Two DPF devices, one with a 750 µm copper anode radius and the other with a 100 µm tungsten anode radius, have been tested using a pulse generating system capable of up to 4 J/pulse with peak voltages of 20 kV and controllable voltage rise rates up to 20 kV/ns. An ICCD camera capable of 0.2 ns gating is used to acquire image series with high temporal resolution. Time resolved imaging of the DPF breakdown and rundown phases at various pressures and total energies, as shown in Figure 1, are used to determine the most suitable pinch conditions. The energy density and drive parameters are calculated for both DPF devices and compared to values typical of other pinch devices, such as the PF-400J and the PF-50J1.