Permanent-Magnet Helicon Discharge Array

Industrial applications of plasmas often require uniform coverage of large areas, such as in plasma coatings, display panels, and semiconductor wafers. A single source would have to be very large, but an array of small sources can be much more compact and yet cover an arbitrarily large area. Such sources can be inductively coupled plasmas (ICPs) which are powered by radio-frequency generators. Helicon-wave sources have been found to create higher plasma densities than ICPs at the same power, but these require a dc magnetic field, which normally would entail large and heavy electromagnets and their dc power supplies. Annular permanent magnets can produce helicon plasmas if used in the innovative way described here. An eight-tube array of such sources has been built and tested.