Phase Resolved Imaging of a Repetitive Extrusion of Hydrogen Plasma From a Hollow Cathode Source

Hydrogen plasmas are useful in many areas of materials processing. In this paper, a hydrogen plasma is produced in a hollow cathode source and its expansion into a chamber over the course of an RF cycle (80 ns) is observed with an intensified CCD camera. The source is observed to launch plasma down into the expansion region once per RF cycle. The shape of the extrusion suggests a surface wave carries charge down the inside of the glass tube, before the plasma collapses back to the center of the tube downstream from the source. At the end of the RF cycle, the plasma in the tube is seen to completely detach from the source plasma.