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Drift of Adsorbed TH on W Filaments Heated with d.c.

Drift of Adsorbed TH on W Filaments Heated with d.c. A study (soon to be reported) of the surface structure produced on tungsten lamp filaments during long heating with direct current has suggested that W ions drift over the wire surface toward the negative terminal. Such migration can be demonstrated directly, for the case of Th adsorbed on W, in a simple electron-optical tube. A loop of 1 mil thoriated wire 6 mm long is mounted on 30-mil leads at the center of a spherical bulb 3 inches in diameter coated inside with willemite. The anode, a wire ring near the mouth of the bulb, is made a few thousand volts positive, and the emitted electrons form on the screen a magnified orthogonal image of the loop; the screen is kept near anode potential by secondary emission. A 10-mil Ni wire, welded to one filament lead and projecting between the ends of the loop, casts an electrical shadow which permits distinguishing the emission from the two ends, and also prevents evaporation of Th from one end across to the other. With the anode floating, the filament is first flashed and then is heated, from a 2 v d.c. supply, for 20 or 30 minutes at a low activating http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review American Physical Society (APS)

Drift of Adsorbed TH on W Filaments Heated with d.c.

Johnson, R. P
Physical Review , Volume 53 (9) – May 1, 1938
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Publisher
American Physical Society (APS)
Copyright
Copyright © 1938 The American Physical Society
ISSN
1536-6065
DOI
10.1103/PhysRev.53.766
Publisher site
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Abstract

A study (soon to be reported) of the surface structure produced on tungsten lamp filaments during long heating with direct current has suggested that W ions drift over the wire surface toward the negative terminal. Such migration can be demonstrated directly, for the case of Th adsorbed on W, in a simple electron-optical tube. A loop of 1 mil thoriated wire 6 mm long is mounted on 30-mil leads at the center of a spherical bulb 3 inches in diameter coated inside with willemite. The anode, a wire ring near the mouth of the bulb, is made a few thousand volts positive, and the emitted electrons form on the screen a magnified orthogonal image of the loop; the screen is kept near anode potential by secondary emission. A 10-mil Ni wire, welded to one filament lead and projecting between the ends of the loop, casts an electrical shadow which permits distinguishing the emission from the two ends, and also prevents evaporation of Th from one end across to the other. With the anode floating, the filament is first flashed and then is heated, from a 2 v d.c. supply, for 20 or 30 minutes at a low activating

Journal

Physical Review – American Physical Society (APS)

Published: May 1, 1938

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