Resistive MHD Modeling of a Coaxial Plasma Gun With a Gas Puff Inlet

A coaxial plasma gun (CPG) is a cylindrically symmetric, pulsed power device that forms an axially propagating plasma sheath. They are often used in applications where plasma formation and/or acceleration are required, such as in material processing, space propulsion, and nuclear fusion reactors. A custom CPG was constructed for the purpose of investigating resistive torsional fan magnetic reconnection. For this investigation, it is a design requirement to reliably produce a plasma sheath from a snowplow. Through gas puff operation in a low pressure environment (0.7 Torr), a transition of the plasma from a deflagration mode into a snowplow mode was observed using high-speed camera imaging and Rogowski coil diagnostics. This observation is further supported by numerically solving the resistive MHD equations using laboratory conditions during the CPG operation. The results of these simulations are qualitatively compared to the high-speed camera images obtained and used to bolster the argument that a transition of the plasma from gas puff initiated plasma deflagration into a snowplow plasma sheath formation is occurring as observed. Additionally, the simulation helps constrain the experimental timing of introducing an external magnetic field to interact with the snowplow mode.