Current Density at the Cathode Spot of the Mercury Arc


LAST July, I observed that the cathode 'spot' of the transient arc obtained by discharging a condenser through a vacuum tube with mercury cathode took the form (a few microseconds after initiation) of a number of very small spots. The current density of emission appeared at least 100,000 amp. per sq. cm., however prolonged the discharge and however nearly the characteristics of the discharge approached those of a normal arc. These results were obtained from low-power photomicrographs (up to × 25) using a Kerr cell shutter giving an exposure of one microsecond.

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    Loeb, "Fundamental Processes of Electrical Discharge in Gases", 629 (John Wiley, 1939).

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    Teago and Gill, "Mercury Arcs", 12 (Methuen, 1936).

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FROOME, K. Current Density at the Cathode Spot of the Mercury Arc. Nature 157, 446 (1946) doi:10.1038/157446b0

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