Extended Magnetohydrodynamic Effects on Dynamics and Stability of Magnetically Driven High Energy Density Plasma Jets

A novel experiment resembling a planar plasma gun has been developed to produce magnetically driven high-energy-density (HED) plasma jets on the 1 MA, 220 ns rise time COBRA generator at Cornell University. The experimental setup consists of a central pin electrode that injects a single gas puff on axis, surrounded by a second annular electrode with a continuous gas injection slit. A permanent ring magnet is housed within the central electrode to provide an initial poloidal magnetic field which links the two electrodes. In this way, the experiment mimics a magnetized central object such as a star or blackhole surrounded by a rotating accretion disk. The resulting free-boundary, high aspect ratio plasma jets strongly resemble naturally occurring astrophysical jets. Here, we investigate extended magnetohydrodynamic (XMHD) effects on jet dynamics and stability via the ability to have the cathode as the central pin electrode and anode as the annular electrode or vice versa with the added flexibility to reverse the polarity of the background poloidal magnetic field independently of the cathode and anode. Measurements of densities, temperatures, velocities, and magnetic fields are collected using Thomason scattering, B-dot probes, Faraday rotation, laser interferometry, and optical spectroscopy. The experimental results are supported by 3D modelling using PERSEUS an XMHD code; simulation results are used to study the evolution of canonical fields, flux tubes, and helicity in the plasma jets.