Structure and dynamics of quasi-Keplerian, differentially rotating HED laboratory plasmas *

We present results from the Rotating Plasma Experiment (RPX) developed on the MAGPIE pulsed-power generator (1.4 MA, 500 ns duration). The goal is to interpret and model the rotation profile and pressure balance of differentially rotating plasmas driven by the slightly off-radial inward-convergence of 8 magnetized ablation flows.

The data shows that rotating plasmas have a hollow density structure and are radially confined by the ram pressure of the ablation flows. A combination of axial thermal and magnetic pressure launches an axial, highly collimated, supersonic jet with a velocity ~ 100 km/s (M > 5). The axial jet also rotates, transporting angular momentum, as it remains collimated by a hot (T_i ~ 200 eV) surrounding plasma halo. Rotation velocities are transonic (M ~ 1), with a radial distribution such that angular frequency decreases with radius, as the opposite happens to angular momentum. This implies that the flows at RPX are quasi-Keplerian, sharing stability properties of gravitationally driven accretion disks.