Stable magnetically driven plasma jets on the 1-MA COBRA generator*

Collimated plasma jets appear to be a ubiquitous feature of the universe, developing over a vast range of scale lengths and source energies. However, common features suggest universal mechanisms may be responsible for jet formation, collimation, and stability. No single model of jet formation is universally accepted to account for the extreme length and stability observed in many jets; however, theory, astrophysical observations, and recent laboratory experiments suggest that some jets may represent magnetically driven configurations that form self-organized equilibria with stabilizing shear flows. To test this hypothesis, a platform has been developed for the 1-MA, 220-ns rise time COBRA generator. In contrast to previous high-energy-density laboratory jet experiments that use radial/conical wire arrays or foils, this experiment uses azimuthally symmetric gas-puff injection. This avoids the ablation phase from a solid target, provides a continuous mass source, and allows for free rotation of the jet foot-points. A permanent magnet provides an initial poloidal magnetic field which links the two concentric electrodes and mimics the boundary conditions of a star-accretion disk system. Here we present the design of the experiment and measurements of the resulting stable, high-aspect ratio jets taken using optical Thomson scattering, laser interferometry, Faraday polarimetry, and B-dot probes. Results are compared to 3D simulations using the PERSEUS extended magnetohydrodynamics (XMHD) code.