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Helicon waves in a plasma confined by a cylinder are treated. The undamped normal modes of the helicon (H) and Trivelpiece-Gould (TG) waves have distinctly different wave patterns at high magnetic fields but at low fields have similar patterns and therefore interact strongly. Damping of these modes, their excitation by antennas, and the RF plasma absorption efficiency are considered. Nonuniform plasmas are treated by solving a fourth order ordinary differential equation numerically. A significant difference between this and earlier codes which divide the plasma into uniform shells is made clear. Excitation of the weakly damped H wave, followed by conversion to the strongly damped TG wave which leads to high helicon discharge efficiency, is examined for realistic density profiles. A reason for the greater heating efficiency of the m = +1 versus the m = -1 mode for axially peaked profiles is provided.

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Helicon waves are waves in low-temperature, partially ionized plasmas in a dc magnetic field (B-field). The study of helicons involves both ion-neutral collisions and Larmor orbits, even when the B-field is uniform. Helicon discharges are ionized by helicon waves generated by a radiofrequency (RF) antenna. Interest in helicon discharges arose because of the high plasma densities they generate compared with other RF sources at comparable powers. The semiconductor industry has not taken advantage of this, even since the possible use of permanent magnets for the B-field has been demonstrated. Nonetheless, a large literature on helicons has evolved because of the numerous problems these discharges posed and the interesting physics found in their solutions.

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