Abstract
Five distinct discharge modes are observed in a cylindrically-symmetric helicon reactor. Each mode is characterized by its plasma impedance, wave mode structure, density distribution and floating potential structure. It is shown that the lowest two modes are capacitive (E) and inductive (H), while higher modes are helicon wave (W) modes. Successive wave modes are found to correspond to helicon wave cavity resonances of the plasma-filled vacuum vessel, each with a well defined wavevector, density and impedance. Measured wavevectors and densities are in agreement with the helicon wave dispersion relation. The first helicon discharge mode is found to be an m = ±1 mode, as expected for a double saddle field antenna. Unexpectedly, the second and third helicon modes have an m = 0 azimuthal symmetry.
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