Three-grid accelerator system for an ion propulsion engine
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorJohn R. Brophy
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Abstract
Apparatus for an ion engine comprises a three-grid accelerator system with the decelerator grid biased negative of the beam plasma. This arrangement substantially reduces the charge-exchange ion current reaching the accelerator grid at high tank pressures, which minimizes erosion of the accelerator grid due to charge-exchange ion sputtering, known to be the major accelerator grid wear mechanism. An improved method for life testing ion engines is also provided using the disclosed apparatus. In addition, the invention can also be applied in materials processing.
Claims4
In an accelerator system for an ion propulsion engine including an anode, a cathode, a first, screen grid, a second, accelerator grid, and a neutralizer cathode, an improvement comprising:
- a third, decelerator grid disposed between said accelerator grid and an ion exhaust stream exiting said engine, said decelerator grid being at a lower electrical potential than said neutralizer cathode and at a higher electrical potential than said accelerator grid.
Dependencies are inferred from the claim text.