EXCITATION, CONVERSION AND DAMPING OF WAVES IN A HELICON PLASMA SOURCE DRIVEN BY AN M=0 ANTENNA

The excitation of a helicon plasma source by an azimuthally symmetric antenna is considered in comparison with anti-symmetric excitation. Th e resonances and anti-resonances at the wave excitation, as well as th e peculiarities of the power absorption, are shown to be very similar for symmetric and anti-symmetric excitation. The plasma resistance tur ns out to be higher in the case of symmetric excitation for very short devices. The non-monotonic variation of plasma resistance with densit y is found to be intrinsic for both methods of excitation as a result of decreasing the power absorption at anti-resonances, This is shown t o give rise to abrupt density jumps at varying input power.