Propagation and Absorption of Electromagnetic Waves in Inhomogeneous Helicon Plasmas with a Lower Hybrid Resonance Layer

Propagation and absorption of radiofrequency waves are numerically studied for radially inhomogeneous helicon plasmas with a lower hybrid resonance layer. The rf power is absorbed outside the resonance layer and the peak absorption occurs near the resonance at a low collision frequency. As the collision frequency increases, the absorption peak moves toward the plasma boundary. The plasma resistance is examined as functions of the density and the magnetic field. The density giving a high plasma resistance is proportional to the magnetic field for a wide range of the magnetic field, including the lower hybrid resonance, if the density profile is sufficiently steep.