Spatiotemporal distribution of hydrogenous electrode vacuum arc discharge plasma

Abstract

Vacuum arc ion sources have been used in a wide range including vacuum coating, materials surface modification, switching devices and other fields. At present, researches on the vacuum arc ion source are mainly targeting the pure metal or alloy electrodes, but the researches on the hydrogenous electrode are rarely reported. The axial and radial distributions of the hydrogenous electrode vacuum arc discharge plasma are studied by using high speed four-frame camera equipped with the narrow-band filters of strong lines of H I and Ti I. It is found that the anode is intensively luminous in the vacuum breakdown. The observation from the camera with the filter reveals that the vacuum breakdown is ignited mainly by the anode hydrogen desorption. The vacuum arc is sustained by plasmas emitted from either the cathode spots or the electrode inner wall. The cone-shaped cathode spot located at the cathode-insulator-vacuum junction is the main plasma source. It is found that the distribution of hydrogen atoms is much more homogeneous than that of titanium atoms, which may be due to the earlier beginning of hydrogen desorption, the bigger emitting area and faster diffusion speed of hydrogen atom.