Extended MHD plasma jets with external magnetic fields

In the present research, collimated plasma jets form from Joule heating and ablation of a radial foil (Al 20 μm thin disk) using a pulsed power generator (COBRA) with 1 MA peak current and 100 ns rise time. Plasma dynamics of the jet are diagnosed with and without an applied uniform external magnetic field (∼1 T axial Bz) and under a change of current polarities, which correspond to current moving either radially outward or inward from the foil's central axis. Experimental results are compared with predictions made by numerical simulations (PERSEUS) 1 . The influence of the Hall effect on the jet development is observed under opposite current polarities. Before jet formation, initial plasma on top of the foil surface develops discrete narrow current path channels (tendrils) that display characteristics of electrothermal-filamentation plasma instability. A disruption of the tendrils and subsequent jet is noticed after a modest increase in the applied field strength from 1 to 1.5 T, which is not predicted by the 2D (r-z) simulations.