Dynamics and Stability of Magnetically Driven High Energy Density Astrophysical Laboratory Plasma Jets on the 1-MA COBRA Generator*

Astrophysical jets develop over a vast range of source energies and scale lengths with many having common features that suggest there may be universal mechanisms which are responsible for jet formation and stability. To investigate these mechanisms, a novel experiment resembling a planar plasma gun has been developed to produce magnetically driven high-energy-density plasma jets on the 1 MA, 220 ns rise time COBRA generator. The experimental setup consists of two concentric planar brass electrodes with gas injected directly into vacuum via a central gas line and azimuthally continuous slit. A permanent ring magnet can be housed within the central electrode to provide an initial poloidal magnetic field which links the two electrodes and captures the basic dynamics of a central engine-disk system with the winding of poloidal field lines from disk rotation. The resulting free-boundary, high-aspect ratio (>50:1) plasma jets remain stable for hundreds of nanoseconds, achieve lengths >5 cm, and strongly resemble naturally occurring astrophysical jets. Here, we present the design of the experiment and measurements obtained using laser interferometry, Faraday rotation, B-dot probes, Thomson scattering, and self-emission imaging. We demonstrate that jet parameters reasonably scale to their astrophysical counterparts. The experimental results are used to benchmark 3D PERSEUS XMHD simulations with the goal of quantifying the injection and transport of relative canonical helicity.