ECR Heating of a Dense Plasma by Helicon Waves

Eigenmodes of an axisymmetric plasma column that is uniform along the magnetic field are investigated. It is shown that, as the plasma density increases, eigenmodes with frequencies close to the electron gyrofrequency tend to localize at the plasma periphery. This effect is likely to restrict the electron density at which the plasma can be heated by means of such modes. A theory is developed for the excitation of the eigenmodes of a plasma column in a weakly nonuniform magnetic field by an external antenna.