Observation of a field orientation dependent instability in preconditioned wire obstacles*

We present experiments from a new pulsed-power driven platform demonstrating interactions of magnetized, supersonic plasma flows with low-ionization plasma columns formed by pre-pulsed wire targets.

The setup delivers a ~100 kA, 10 ns pulse to the target wire (10-100 µm Ø), forming an expanded column with low density contrast relative to the impinging magnetized flow from an exploding wire array. This allows both the study of the formation of instabilities at the media interface, as well as the redistribution of the entrained wire material in the downstream flow.

The orientation of the wires relative to the embedded field lines in the flow is found to play a key part in instability formation. Laser probing diagnostics reveal that when the field is perpendicular to the wire, a well-defined, periodic instability (λ ~ column Ø) is observed with K along the wire.

We discuss the possible mechanisms for this instability and the effects of experimentally varied parameters such as the obstacle diameter and material.