Interaction dynamics of hollow cathode discharge plasmas

Summary form only given, as follows. An experiment was set up for the study of arc dynamics and the interaction between two arcs. Two pairs of electrodes placed inside a bell jar having a height 30 in and a diameter of 18 in were used for electrical discharge. Argon plasma was produced in a background pressure of 1 to 10 torr through a steady-state hollow cathode discharge where the cathode was made of tantalum tubing, allowing argon gas to flow through. The separations among these electrodes were 8 in vertically and 4 in horizontally. The current of each arc was about 10 A. The diameter of each arc column varied from 2 to 4 cm for the constricted mode to a few inches for the diffused mode. The arcs are in the constricted mode when the operating current is high. Constricted arcs are more stable, except sometimes these two arcs may merge in the central region through the pinch effect. A striation along the constricted arc column was also observed frequently. It is confirmed that global modes can be generated by thermal instability in a constricted arc