Thermionic Properties of Uranium

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Abstract
Thermionic measurements were made on uranium metal in the form of drawn wire and on films of uraniumdeposited on tungsten by evaporation in ultrahigh vacua. Measurements of the emission current as a function of accelerating potential and of the work function of the bulk material indicated that the surface was never completely freed of oxide. Measurements of the work function and emission constant A as a function of the thickness of the evaporated films showed both φ and A to increase with increasing depth of deposit up to 15 atom layers and to reach constant values of 3.47±0.03 ev and 114±12 amp cm—2 deg—2, respectively, for deposits 15–200 atom layers deep. Qualitative measurements of the ionization potential of uranium by means of surface ionization showed the positive ion current to increase with increasing temperature indicating the ionization potential to be greater than 4.53 ev. The magnitude of the positive ion currents suggested an ionization potential of 4.5–5.0 volts.

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