A plasma source is provided. The plasma source includes at least three hollow cathodes, including a first hollow cathode, a second hollow cathode, and a third hollow cathode, each hollow cathode having a plasma exit region. The plasma source includes a source of power capable of producing multiple output waves, including a first output wave, a second output wave, and a third output wave, wherein the first output wave and the second output wave are out of phase, the second output wave and the third output wave are out of phase, and the first output wave and the third output wave are out of phase. Each hollow cathode is electrically connected to the source of power such that the first hollow cathode is electrically connected to the first output wave, the second hollow cathode is electrically connected to the second output wave, and the third hollow cathode is electrically connected to the third output wave. Electrical current flows between the at least three hollow cathodes that are out of electrical phase. The plasma source is capable of generating a plasma between the hollow cathodes.