ELECTRON BEAM SOURCE INCLUDING A PILOT NONTHERMIONIC, ELECTRON SOURCE
First Claim
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1. An electron beam gun comprising:
- (A) a pilot gun having (i) An enclosure provided with a relatively low-pressure ionizable gaseous medium providing the source of electrons from said pilot gun;
(ii) A pilot cathode positioned in one wall of said enclosure, said pilot cathode having a concave surface to give a convergent beam of electrons having a focal point beyond the Faraday dark space;
(iii) A pilot anode positioned in said wall around and spaced from said pilot cathode the potential difference between said pilot cathode and pilot anode providing the electron accelerating voltage for the electrons generated from said gaseous medium. (B) A main cathode at the same potential as said pilot anode positioned in the wall opposite said pilot cathode and at a distance from said pilot cathode beyond the Faraday dark space such that said main cathode is bombarded by electrons from said pilot gun and thereby itself emits electrons. (C) A main anode spaced from said main cathode and having a high electron accelerating voltage therebetween to accelerate the electrons emitted from said main cathode toward a workpiece.
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Abstract
A device for generating an electron beam including a pilot gun which generates a pilot electron beam by nonthermionic means. The pilot electron beam is used to bombard a main cathode from which a main electron beam is generated.
29 Citations
7 Claims
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1. An electron beam gun comprising:
- (A) a pilot gun having (i) An enclosure provided with a relatively low-pressure ionizable gaseous medium providing the source of electrons from said pilot gun;
(ii) A pilot cathode positioned in one wall of said enclosure, said pilot cathode having a concave surface to give a convergent beam of electrons having a focal point beyond the Faraday dark space;
(iii) A pilot anode positioned in said wall around and spaced from said pilot cathode the potential difference between said pilot cathode and pilot anode providing the electron accelerating voltage for the electrons generated from said gaseous medium. (B) A main cathode at the same potential as said pilot anode positioned in the wall opposite said pilot cathode and at a distance from said pilot cathode beyond the Faraday dark space such that said main cathode is bombarded by electrons from said pilot gun and thereby itself emits electrons. (C) A main anode spaced from said main cathode and having a high electron accelerating voltage therebetween to accelerate the electrons emitted from said main cathode toward a workpiece.
- (A) a pilot gun having (i) An enclosure provided with a relatively low-pressure ionizable gaseous medium providing the source of electrons from said pilot gun;
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2. An Electron beam gun according to claim 1 wherein said pilot cathode has a concave surface whose radius of curvature is approximately twice the cathode radius.
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3. An electron beam gun according to claim 1 including means for flowing gas from a source thereof into said enclosure to provide and maintain said low-pressure ionizable gaseous medium.
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4. An electron beam gun according to claim 1 including a self-contained source of gas in said enclosure.
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5. An electron beam gun according to claim 3 and including a control ring positioned in said wall around said means for flowing gas into said enclosure and in contact with the Faraday dark space when the gun is in operation to thereby carry a high negative potential which repels electrons.
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6. An electron beam gun according to claim 4 having a control cup fitted with an aperture at the bottom, in proximity to and in line with the cathode emitter for the purpose of aiding in the stabilization of the focal region of the beam, is positioned in said enclosure.
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7. An electron beam gun according to claim 1 wherein power is supplied to said pilot gun through power cables having an outside diameter of about 0.250 and a conductor of as small as 400 circular mils cross section.
Specification