Importance

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Abstract

A method and apparatus is disclosed for producing a gas pumping plasma within an evacuated enclosure having a collimating system consisting of baffle structures and a magnetic field having a central uniform region connected to a source of neutral gas, a magnetic mirror intermediate region and a terminating divergent region. According to the method and apparatus of the present invention, the enclosure is evacuated to a selected pressure, high frequency microwave energy of a selected power and frequency is fed into the magnetic mirror intermediate region, the magnetic field is established at a strength such that an electron cyclotron frequency is made equal to the frequency of the microwave energy within the intermediate region, electrons within the magnetic mirror intermediate region being heated by the microwave energy, the heated electrons ionizing the neutral gas in the intermediate and central regions for creating and maintaining a pumping plasma. Baffle structures are provided between the central and intermediate regions and between the intermediate and terminal regions for permitting unobstructed flow of plasma along the magnetic field lines to the terminal region while restricting inward flow of neutral gas resulting from recombination in the terminal region. The plasma is preferably composed of ionized neutral gas from the central and intermediate regions and an adequate neutral gas concentration is maintained in the intermediate region by controlled supply of make-up gas.

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First Claim