Device for producing an electron beam

{
  "publication_number": "US2013162134A1",
  "country": "US",
  "kind": "A1",
  "title": "Device for producing an electron beam",
  "abstract": "The invention relates to a device for producing an electron beam, comprising a housing (12), which delimits a space (13) that can be evacuated and has an electron beam outlet opening; an inlet (16) for feeding a process gas into the space (13) that can be evacuated; a planar cathode (14) and an anode (15), which are arranged in the space (13) that can be evacuated and between which a glow-discharge plasma can be produced by means of an applied electrical voltage, wherein ions can be accelerated from the glow-discharge plasma onto the surface of the cathode (14). The cathode has a first part (14 a) made of a first material, which forms a centrally arranged first surface region of the cathode (14), and a second part (14 b) made of a second material, which forms a second surface region of the cathode (14) that encloses the first surface region. The first material can be heated by the impingement with accelerated ions to a temperature at which electrons escape the first material predominantly due to thermionic emission.",
  "claims": [
    "1. Device for producing an electron beam, comprising a housing (12), which delimits a space (13) that can be evacuated and has an electron beam outlet opening; an inlet (16) for feeding a process gas into the space (13) that can be evacuated; a planar cathode (14) and an anode (15), which are arranged in the space (13) that can be evacuated and between which a glow discharge plasma can be produced by means of an applied electrical voltage, wherein ions can be accelerated from the glow discharge plasma onto the surface of the cathode (14) and electrons emitted by the cathode can be accelerated into the glow discharge plasma, characterized in that a) a first part (14 a) of the cathode (14) is made of a first material at least on the emission side, which forms a centrally arranged first surface region of the cathode (14); b) a second part (14 b) of the cathode (14) is made of a second material, which forms a second surface region of the cathode (14) that encloses the first surface region; c) the first material is electrically conductive and has an electron work function less than 4 eV; d) the second material is electrically conductive and has an electron work function greater than 4 eV; e) the first material can be heated by the impingement with accelerated ions to a temperature at which electrons escape from the first material predominantly due to thermionic emission. 2. Device according to claim 1, characterized in that the first surface region is designed to be flat. 3. Device according to claim 1, characterized in that the first surface region is designed to be concave. 4. Device according to claim 1, characterized in that the second surface region enclosing the first region is designed to be concave. 5. Device according to claim 1, characterized in that the first material comprises a rare earth boride. 6. Device according to claim 1, characterized in that the first surface region is formed by a solid molded body (14 a) made of the first material. 7. Device according to claim 1, characterized in that the first surface region is a constituent of a composite body. 8. Device according to claim 1, characterized in that the second material comprises graphite. 9. Device according to claim 1, characterized in that the second material comprises a metal. 10. Device according to claim 1, characterized in that the first and the second surface regions are separated by a circumferential gap around the first surface region. 11. Device according to claim 1, characterized in that at least the first material is thermally insulated by a rear-side thermal barrier of cooled parts of the device. 12. Device according to claim 1, characterized in that the thermal barrier comprises at least one gap (44; 54) that can be evacuated and/or a thermal insulator (18; 56). 13. Device according to claim 1, characterized in that the process gas of the glow discharge is an inert gas or hydrogen. 14. Device according to claim 1, characterized in that the beam power thereof can be controlled in the case of constant or pulsed operating voltage by means of varying the process gas flow of the glow discharge. 15. Device according to claim 1, characterized by an electrical insulator body (19; 48; 58) which has cooling channels (19 a) separated from the cathode potential and a vacuum-tight high-voltage lead-through (19 b). 16. Device according to claim 1, characterized in that the propagation direction of the electron beam (17) in the cathode chamber (13) can be controlled by a transverse magnetic field produced by means of a magnetic coil system (11 b) in the region between the cathode (14) and anode (15). 17. Device according to claim 15, characterized in that the insulator body is made of a synthetic material (48), of an oxide ceramic or of aluminum nitride (58)."
  ],
  "cpc": [
    "H01J 37/075",
    "H01J 2237/3104",
    "H01J 2237/3128",
    "H01J 2237/3132",
    "H01J 29/006",
    "H01J 29/563",
    "H01J 3/025",
    "H01J 37/077"
  ],
  "assignees": [
    "MATTAUSCH GOESTA",
    "FEINAEUGLE PETER",
    "KIRCHHOFF VOLKER",
    "WEISKE DIETER",
    "FLASKE HENRIK",
    "ZEIBE RAINER"
  ],
  "filing_date": "2011-09-08",
  "publication_date": "2013-06-27",
  "priority_date": "2010-10-25",
  "application_number": "US-201113821887-A",
  "family_id": "44741253"
}