ION SOURCE
First Claim
1. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons from said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, means for concentrating said electron flow to create a region within said ionization region where the electron flux is a maximum, wherein said gas supply path terminates in at least one aperture disposed in proximity to said region of maximum electron flux.
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Abstract
An ion source 10 for producing a beam of ions from a plasma is disclosed. A plasma is created at the centre of an anode 12 by collisions between energetic electrons and molecules of an ionizable gas. The electrons are sourced from a cathode filament 11 and are accelerated to the anode 12 by an applied electric potential. A projection of the anode and a magnetic field having an axis aligned with the axis of the anode act together to concentrate the flow of electrons to the centre of the anode 12. The ionizable gas is introduced into an ionization region 13 of the ion source 10 at the point of concentrated electron flow. Ions created in the ionization region are expelled from the ion source as an ion beam centred on the axis of the magnetic field. The surfaces of the anode are coated with an electrically conductive non-oxidising layer of Titanium Nitride to prevent a build up of an insulating layer on the anode.
8 Citations
53 Claims
- 1. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons from said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, means for concentrating said electron flow to create a region within said ionization region where the electron flux is a maximum, wherein said gas supply path terminates in at least one aperture disposed in proximity to said region of maximum electron flux.
- 20. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons from said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, wherein said anode has at least one surface exposed to said ionization region, at least a portion of said at least one surface being of an electrically conductive non-oxidizing material.
- 25. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons produced by said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, wherein said gas supply path comprises a gas line terminating in an electrically conductive outlet member disposed within the ionisation region, said outlet member having one or more apertures therein for providing communication of gas from the gas line to the ionization region, and wherein said outlet member is in electrical contact with said anode.
- 31. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons produced by said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, wherein said anode comprises an end wall, a side wall extending from the end wall in the direction of the cathode and sloping outwardly in the direction from the end wall toward the cathode such that the end wall and side wall together define a substantially conical ionization region with a closed end at the end wall and with an open end toward the cathode, and wherein said gas supply path comprises one or more channels extending through said anode side wall, each of said channels terminating at an aperture disposed substantially adjacent said end wall.
- 35. An ion source comprising an electron producing cathode, an anode, an ionization region between said cathode and said anode, a gas supply path for introducing an ionizable gas into said ionization region, means for creating a potential difference between said cathode and said anode to produce a flow of electrons produced by said cathode toward said anode, said electron flow passing substantially through said ionization region and causing ionization of said gas, said potential difference also acting to expel ions created in said ionization region from said ion source, wherein said anode comprises an end wall, a side wall extending from the end wall in the direction of the cathode and sloping outwardly in the direction from the end wall toward the cathode such that the end wall and side wall together define a substantially conical ionization region with a closed end at the end wall and with an open end toward the cathode, and wherein said gas supply path comprises one or more tubes extending into said ionization region, each tube terminating in an aperture disposed adjacent the end wall.
- 40. An anode for an ion source, the anode comprising an end wall, a side wall extending from the end wall and sloping outwardly in the direction away from the end wall such that the end wall and side wall together define a substantially conical region with a closed end at the end wall and with an open end at an end of the anode opposite the end wall.
Specification