Ion Erosion Rate in a High Current Vacuum Spark

Measurements of the ion erosion rate for copper cathode in the low-inductance vacuum spark are presented. The spark peak current was varied from 3 kA up to 13 kA therewith the current rise rate increases from 4middot10⁹ up to 1.5middot10¹⁰ A/s. The mean velocity of the cathode plasma flame was obtained by means of the passive collector time-of-flight measurements. It was shown that the velocity increases from 2middot10⁴ m/s up to 8middot10 ⁴ m/s with the discharge enhancement. Mechanical momentum of the plasma flame was measured with a ballistic pendulum, located beyond annual anode in the immediate vicinity. From these data the ion erosion rate was derived at range of peaks of the discharge current mentioned above. This parameter holds to within the accuracy of measurements throughout the range of the current variations. Its value is of 7middot10^-5 g/Q and is close to the well-known one that has been obtained earlier in low-current vacuum arcs