Self-magnetic drive of a shunting arc

A magnetically driven shunting arc as a pulsed metal/solid plasma source has been newly developed. This article describes fundamental electrical and plasma dynamic characteristics of the magnetically driven arc. The shunting arc plasma has a feature of self-ignition without using any triggering mechanism method at a wide gas pressure range from vacuum to atmospheric pressure. The plasma pre-cursors are emitted around the rod by joule heating of the rod before electrical breakdown by a glow-like discharge or a surface-running discharge along a rod, and finally an arc discharge is made. The generated arc plasma is driven by the self magnetic field generated by the arc current itself. The pilot system consisted of the 120-mm-long carbon rails as electrodes and a 40-mm carbon rod as solid plasma source material. A 20-μF capacitor was employed for applying high current to the rails and the rod. The arc was initiated at the minimum charging voltage of 400 V, in which a sinusoidal waveform of 500 A peak current appeared. The energy required for the arc ignition was almost independent of the charging voltage, but was dependent on the rod position bridged between the rails. The shunting arc plasma was successfully accelerated along the rail and went out towards a target set at 40 mm apart from the muzzle of the shunting arc plasma gun. The running distance of the plasma increased with increasing the charging voltage. The average running velocity was roughly estimated around 1 km/s with the plasma duration of 25 μs.