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Wide area source of multiply ionized atomic or molecular species

  • US 4,737,688 A
  • Filed: 07/22/1986
  • Issued: 04/12/1988
  • Est. Priority Date: 07/22/1986
  • Status: Expired due to Fees
First Claim
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1. Apparatus for providing a wide area source of multiply ionized atomic or molecular species, the apparatus comprising:

  • vacuum chamber means;

    a ring-shaped cold cathode within said vacuum chamber means having a geometrically shaped front surface comprising a material selected for the efficient emmission of secondary electrons and for minimum cathode sputtering, said ring-shaped cold cathode being operative in the abnormal glow discharge state for generating a disc-like plasma;

    a ring-shaped cathode shell coaxially covering an outer surface of said ring-shaped cold cathode;

    a solid planar ion reflecting electrode positioned substantially perpendicular to a circular axis of said ring-shaped cold cathode to reduce the escape of ions from an adjacent first surface of the disc-like plasma;

    one or more extraction grids positioned adjacent a second surface of said disc-like plasma for extracting and accelerating a total ion flux from that surface of said disc-like plasma;

    an ion selector positioned in the path of the total ion flux extracted from the disc-like plasma for selecting a beam of specific ions from the total ion flux;

    power supply means for applying desired voltages to the ring-shaped cold cathode, ion reflecting electrode, and extraction grids;

    vacuum control means coupled to said vacuum chamber means for establishing and maintaining a desired vacuum within the range of 1.0 to 30 Torr within a volume enclosed by said vacuum chamber means that is adjacent said ring-shaped cold cathode;

    differential pumping means coupled to said vacuum chamber means for establishing a differential pressure between a volume enclosed by said vacuum chamber means that is adjacent the ring-shaped cold cathode and another volume that is adjacent the ion selector; and

    gas port means coupled to said vaccum control means and to said differential pumping means for admitting and controlling the flow of selected atomic or molecular feedstock gases into said vacuum chamber means.

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