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Non-ambipolar radio-frequency plasma electron source and systems and methods for generating electron beams

United States Patent

March 3, 2009
View the Complete Patent at the US Patent & Trademark Office
An electron generating device extracts electrons, through an electron sheath, from plasma produced using RF fields. The electron sheath is located near a grounded ring at one end of a negatively biased conducting surface, which is normally a cylinder. Extracted electrons pass through the grounded ring in the presence of a steady state axial magnetic field. Sufficiently large magnetic fields and/or RF power into the plasma allow for helicon plasma generation. The ion loss area is sufficiently large compared to the electron loss area to allow for total non-ambipolar extraction of all electrons leaving the plasma. Voids in the negatively-biased conducting surface allow the time-varying magnetic fields provided by the antenna to inductively couple to the plasma within the conducting surface. The conducting surface acts as a Faraday shield, which reduces any time-varying electric fields from entering the conductive surface, i.e. blocks capacitive coupling between the antenna and the plasma.
Hershkowitz; Noah (Madison, WI), Longmier; Benjamin (Madison, WI), Baalrud; Scott (Madison, WI)
Wisconsin Alumni Research Foundation (Madison, WI)
11/ 427,273
June 28, 2006
The subject matter of this application was made with U.S. Government support awarded by the following agencies: NASA Glenn Research Center, Grant NNC04GA82G and U.S. Department of Energy, Grant DEFG0297ER54437. The United States has certain rights in this invention.