Magnetically controlled vacuum-arc on-off switch

A vacuum spark gap is demonstrated which attains high-power switch-off capability by a magnetic control field applied to the anode in a Penning-type discharge geometry. Applying the magnetic field raises the arc voltage and excites oscillations. Circuit interruption results if the arc current is reduced to the current chopping level of the cathode material. Shunt capacitance raises the interruption ability. Currents up to 9 kA were interrupted. Transient recovery voltages ranged up to 20 kV.