Excitation Processes and the Theory of the Arc Discharge

• DOI: 10.1038/175646a0
• Publication Date: 2006-10-26T14:42:21Z
• Authors: A. E. ROBSON; A. VON ENGEL

No satisfactory theory exists to account for the current transfer at the cathode of an arc the cathode material of which has a low boiling point, such as mercury or copper. Whereas thermionic emission can account for the mechanism of arcs with cathodes of high boiling point, such as carbon and tungsten, this seems highly improbable for substances which boil far below their emitting temperature. Field emission of electrons1, current transfer by positive ions only2, and other suggestions3 have been made; but they cannot account for both the observed high current densities4 of order 106A./cm.2 and the low cathode fall, which can be smaller than the ionization potential of the cathode material5.