High-speed imaging of titanium cathode spots in a high-current vacuum arc thruster

Abstract The apparent movement of plasma emission sites across the cathode surface of a 30 W high-current vacuum arc thruster is examined using high-speed imaging. Images captured at a frame rate of 450 000 fps reveal the temporal evolution of the cathode spot distribution over the course of a single current pulse. Films were recorded with a titanium cathode and a copper anode. A comparison with the discharge current shows a locally high current density, on the order of 10 9 A m −2 . Quantitative analysis on clustering of cathode spots, and the mapping of their trajectory over the cathode surface offer insights into the cathode erosion dynamics.