Coupling to fast eigenmodes in a non-uniform plasma

The dispersion relation and fields of fast magnetosonic waves in a pure deuterium plasma are calculated by using a model that includes the electron mass in the cold-plasma dielectric tensor and a cylindrically symmetric non-uniform density. If the attenuation is small, coupling of antennas to column resonances, or eigenmodes, can be described by two terms — one determined by geometrical factors and the other one by the damping within the cavity. This paper presents calculations of geometrical coupling factors for a quarterturn loop and for a waveguide suitable for present-day tokamak conditions. The method allows for a systematic representation of coupling to the many different possible eigenmodes, independently of the damping mechanism.