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US 4,659,899 AGranted
Vacuum-compatible air-cooled plasma device
AssigneeThe Perkin-Elmer Corporation
InventorsDavid G. Welkie, Robert L. Gerlach
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AssigneeThe Perkin-Elmer Corporation
InventorsDavid G. Welkie, Robert L. Gerlach
Estimating the term…
A plasma generating device, and in particular a duoplasmatron ion gun, is disclosed that is air cooled, high vacuum compatible and hence very clean with a stable ion current output. The device is mounted to a standard type flange held at ground potential without the necessity of subsequent high voltage isolation. Cooling is achieved with cooling fins and a fan inside a housing in which the duoplasmatron is mounted. A mounting structure includes a vacuum tight ceramic ring brazed between the mounting flange and the gun body. The ceramic ring is located with respect to high permeability magnetic components and a magnetic coil to facilitate a magnetic field for focusing the plasma, allowing the coil to be referenced to ground potential while the gun is maintained at high voltage. A ceramic chamber containing ceramic pellets is located in the plasma-forming gas inlet duct to prevent high voltage electrical discharge in the gas duct. A piezoelectric valve operated by a pressure sensor maintains accurate gas flow and ion output.
A plasma generating device for use as a source of ions while operating at high vacuum and at high voltage relative to an ion extracting system, comprising:
A conduit for conveying gas at low pressure between an external source of gas and a device maintained at high voltage relative to the external gas source without gaseous discharge occurring in the conduit, said conduit extending from the external gas source to the device and comprising an electrically insulating container, a multiplicity of electrically insulating pellets in a multiplicity of layers filling the cross-section of the container, and retention means disposed at opposite ends of the container having a multiplicity of orifices therein to retain the pellets while readily conveying the gas therethrough, the pellets being packed with their adjacent surfaces separated by maximum distances that are less than the average path length of electrons and ions in a low pressure gas in the conduit such as to prevent electrical discharge in the gas.
Dependencies are inferred from the claim text.