Hollow cathode
First Claim
1. In an electron beam apparatus, the improvement which comprises a hollow cathode structure comprising an outer enclosure, having at one end thereof a wall, said wall having an aperture therethrough for electron beam emission, a second wall at the opposite end of said enclosure, the enclosure and walls defining an interior chamber, means for admitting an ionizable gas into said chamber, the interior surface of said chamber, exclusive of said end walls, having a low work function electron emissive coating thereon which readily emits electrons under bombardment by ions from said gas, and means for ionizing the gas within said chamber whereby high energy electrons are emitted from said surface by secondary emission effects and low energy electrons released by collision between said high energy electrons and gas ions are emitted through the aperture.
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Accused Products
Abstract
A long life high current density hollow cathode electron beam source for use in various E-beam apparatus which uses an ionizable gas within the hollow cathode. Bombardment of an electron emissive surface within the hollow cathode by energetic gas ions causes electrons to be emitted by secondary emission rather than thermionic emission effects. Once initialized by an external ionization voltage the device is essentially self sustaining and operates near room temperature, rather than at thermionic emission temperatures, and with reduced voltages.
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Citations
9 Claims
- 1. In an electron beam apparatus, the improvement which comprises a hollow cathode structure comprising an outer enclosure, having at one end thereof a wall, said wall having an aperture therethrough for electron beam emission, a second wall at the opposite end of said enclosure, the enclosure and walls defining an interior chamber, means for admitting an ionizable gas into said chamber, the interior surface of said chamber, exclusive of said end walls, having a low work function electron emissive coating thereon which readily emits electrons under bombardment by ions from said gas, and means for ionizing the gas within said chamber whereby high energy electrons are emitted from said surface by secondary emission effects and low energy electrons released by collision between said high energy electrons and gas ions are emitted through the aperture.
- 6. In a electron beam apparatus, the improvement which comprises a hollow cathode structure comprising an outer enclosure, having at one end thereof a wall, said wall having an aperture therethrough for electron beam emission, a second wall at the opposite end of said enclosure, means for admitting an ionizable gas into said chamber, the enclosure and walls defining an interior chamber, at best, some of the interior surfaces of said chamber having a low work function secondary electron emissive coating thereon which readily emits electrons under bombardment by ions from said gas, means for admitting an ionizable gas plasma into said interior chamber, and means for establishing a strong magnetic field transverse to electron beam flow through said aperture in said one end wall whereby energetic electrons are substantially prohibited from passing through said aperture.
Specification