Ignition and instability of low-current DC vacuum arcs ignited by the opening of the electrodes

The ignition, lifetime, and instability of low-current DC vacuum arcs, which were ignited by the opening of the electrodes, were investigated experimentally. Copper electrodes were used and the arc current was less than 50 A. Waveforms of the voltage and current between the electrodes at the moment of arc ignition and during the arc continuation were measured. It was confirmed that, for the ignition of the arc, a voltage which was larger than a critical value should appear between the electrodes at the moment of the opening of the electrodes. The lifetime of the arc is short, less than 1 s in the present condition, and increases with an increase in arc current and output voltage of the current source. The arc voltage consists of a certain DC level, around 20 V, and an additive high-frequency component. The arc current consists of a certain DC level and a subtractive high-frequency component.