Device for providing high-intensity ion or electron beam
AssigneeThe United States of America as represented by the United States Energy Research and Development Administration
InventorsEdwin D. McClanahan, Ronald W. Moss
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Abstract
A thin film of a low-thermionic-work-function material is maintained on the cathode of a device for producing a high-current, low-pressure gas discharge by means of sputter deposition from an auxiliary electrode. The auxiliary electrode includes a surface with a low-work-function material, such as thorium, uranium, plutonium or one of the rare earth elements, facing the cathode but at a disposition and electrical potential so as to extract ions from the gas discharge and sputter the low-work-function material onto the cathode. By continuously replenishing the cathode film, high thermionic emissions and ion plasmas can be realized and maintained over extended operating periods.
Claims10
In a device for producing an ion beam including a gas-tight chamber with means for providing ionizable, inert gas at near vacuum pressures within said chamber, said chamber containing a cathode comprising a heat-resistant material and having an outer electron emissive surface adapted for thermionic emission;
- an anode spaced apart from said cathode;
- said anode and cathode interconnected with a source of sufficient voltage to establish an ionized gas plasma between said electron emissive surface of said cathode and said anode;
- the improvement wherein an auxiliary electrode is disposed with at least one surface exposed to and facing said electron emissive surface of said cathode and positioned so as to be exposed to said ionized gas plasma, said at least one surface of the auxiliary electrode containing a low-work-function material which when dispersed within the electron emissive surface of said cathode material provides a thermionic work function lower than the work function of said cathode material, said cathode and auxiliary electrode being more closely positioned than the positioning of said cathode to said anode and wherein there are provided electrical means for maintaining said auxiliary electrode at a more negative potential than that of said cathode such that ionized gas from said plasma impinges on said one surface of said auxiliary electrode to sputter-deposit said low-work-function material onto said electron emissive surface of said cathode.
Dependencies are inferred from the claim text.