Preliminary Findings from Efforts to Model Pulsed Inductive Theta-Pinch Plasmas Via Particle-In-Cell

A method is pursued to approximately model the electron energy distribution of pulsed inductive plasma devices with Particle-In-Cell code to elucidate formation physics during early times (t \u3c 1 µs). Specifically, reported results from AFRL-Kirtland\u27s pulsed inductive device, FRCHX, are used as a test case to validate results. An r-z slab approximation is outlined and gyro-frequency, Larmor radius, and E×B guiding center drift are verified against theory to within 1% difference. The analyses presented, using both single electron and Particle-In-Cell modeling, agree with FRCHX reported results by showing that average electron kinetic energy does not exceed the ionization threshold of 15.47 eV for gaseous deuterium until after the first ¼ cycle of the ringing pre-ionization stage (when net magnetic field is approximately nullified). These results provide supportive evidence for the concept that bias field actually inhibits ionization if improperly implemente

Reduced reshock growth in a convergent/divergent system: Effect of reshock strength

The Richtmyer-Meshkov instability creates or seeds hydrodynamic instabilities that will mix cold shell material into the hot DT fuel in an ignition capsule and may prevent ignition. Characteristic of this process is multiple shocks crossing converging interfaces. To mimic this situation, strong converging shocks were created, passed over an unstable interface, reflected by an inner cylinder, and then reshocked the interface. Analysis of the mix width at the unstable surface shows no additional growth, within experimental uncertainty, due to an initially perturbed surface and no dependence on reshock strength

Pulse Discharge Network Development for a Heavy Gas Field Reversed Configuration Plasma Device

A simple LRC circuit model is used to conduct a parametric study of the effects of charging voltage, capacitance, resistance, and inductance on the current waveform of a pulse forming network for field reversed configuration (FRC) plasma production. Using known waveforms from existing networks, estimates of realistic values of resistance and inductance are established for a base network model. Parametric modification of the base model is used to study the effects of each component of the discharge network. Results indicate that increasing charging voltage causes an increase in peak current, but does not effect rise or reversal times. However, increasing capacitance increases peak current and increases rise and reversal times. Further, optimum circuit parameters are determined for the design and construction of an FRC formation test article. Three main design criteria are used and are based on magnetic diffusion time, auto-ionization of background gas, and peak magnetic field strength. Results indicate that a pulse forming network with charging voltage of 25 kV and capacitance of 1 μF provides the widest range of resistance and inductance values such that the waveform meets the design criteria. C