The Anode Phenomena of DC Plasma Generator

The intense heat flux to the electrode at the arc turminus dictates the design limitation of arc plasma devices. The energy flux due to the electron current is found to be the dominant mechanism. The net energy transfer to an anode is far noticeable to a cathode. Therefore a considerable effort has expended in attempt to achieve a good understanding of the anode-phenomena. The longitudinally segmented nozzle anode was used to examine the anode phenomena. This anode was composed of the mutually insulated four sections. Each segmented anode current was measured by the ammeter which was set in the individual anode circuit, and its waveform was observed by dual beam synchroscope. At the same time another synchroscope was used to examine the waveform of the arc voltage. In case of the total arc current being 10amp., the arc current was concentrated at a downstream end of the anode throat. Its arc turminus fixed there steadily and its attachment area was small. It was shown that, increasing with the total arc current, the segmented anode current distribution shifts gradually its peak value to the upstream segments of the anode nozzle. For the arc current from 15 to 45amp., the anode spot moved swiftly in the form of the restrike mode. The mean velocity of anode arc turminus which was determined from electrical measurement was of the order of 20?150m/sec. As the gas flow rate a increased, its velocity getting faster. Over 50amp. the steady mode prevailed again, but the anode arc turminus expanded in its size and moved up to the adjacent upstream segments. In case the total current less than 45amp. segmented anode current distribution was independent of the argon gas flow rate. When the total arc current increased over 50amp., the influence of the gas flow rate became considerable, and with increasing the gas flow rate the segmented anode current distribution drifted to the downstream. The arc voltage was dependent on the anode attachment position. As the anode arc turminus shifted to downstream, the value of the arc voltage increased.