Velocities of copper and silver ions generated from an impulse vacuum arc

Vacuum gaps with a copper and silver needle-cathode were fired by a 13 μs duration half-cycle sinusoidal arc and metal ions were analyzed by a time of flight (TOF) method at variable positions of the acceleration space. Velocities of the ions of each charge state were determined assuming collisionless flight from the cathode region to the outside of the gap. Ions generated at the ignition of the arc flew fast and the velocities were 2.7×10⁴ and 2.0×10⁴ m/s for copper and silver, respectively, regardless of the charge state. The velocities of the ions released with the arc extinction were lower and changed depend on the charge state