Retrograde Arc and Cathode Spot Motion in Crossed Electric and Magnetic Fields

摘要

Retrograde Arc and Cathode Spot motions on various electrode configurations were examined in a subatmospheric argon environment. Emphasis was placed on the study of semi-stationary arc modes; especially the arc shape, curvature, and arc channel radii, in addition to cathode spot patterns and frequencies of occurrence. Thermionic arcs with tungsten and carbon cathodes were also investigated. Retrograde motion was observed for the first time for arcs which moved completely around fixed electrodes. The highest known arc currents were also achieved for retrograding arcs. Intensely bright, conically shaped protrusions were found on copper plate electrodes which seem to be part of the cathode spots, or possibly the cathode spots themselves, for certain cases. These conical shapes may be extremely high-pressure cathode vapor. Cathode vapor jets were observed to be driven into the amperian direction in all cases in which a magnetic field was present. Measurements of arc channel radii and current densities for copper electrodes at pressures of 6 and 40 millimeters of mercury are reported.