Anode Modes and Plasma Parameters of Low Current Vacuum Arc

Abstract

Anode mode and arc voltage of Ti cathode N2 vacuum arc are investigated as a function of pressure (10-2-5×102Pa) and arc current (15-150A). New anode mode of luminous surface mode is found and footpoint mode can be steadily realized in this experiment. The following results are obtained. With increasing pressure, anode mode shifts from no-luminous mode to unsteady footpoint mode, steady footpoint mode, luminous surface mode and anode spot mode. As the arc current decreases, the pressure at which the mode shifts decreases.
Plasma parameters in the plasma space between cathode and anode are measured with static electric probes. The following results are obtained. Potential distribution is flat for the no-luminous mode. Anode drop appears for the steady footpoint mode and plasma drop as well as anode drop appears for the luminous surface mode. For the luminous surface mode, electron temperature increases as the electric field increases in the plasma space. From these results, it is considered that the luminance of anode surface is due to the increasing electron temperature in consequence of the increasing electric field near the anode surface.