Alfven wave experiments on the PRETEXT tokamak

The Alfven waves investigated in the PRETEXT tokamak are plasma waves below the ion cyclotron frequency. Three-dimensional plots of their dispersion relations are presented. Alfven waves are of interest since they may serve as a possible supplementary method of plasma heating in tokamak fusion reactors because sources with sufficient power for fusion reactors are presently available at lower cost per watt than are other heating schemes. For efficient coupling, antennas covered a significant portion of the surface of the plasma in order to carefully select the Fourier modes which put energy into desirable portions of the plasma. Two sets of Fourier modes are presented which include the fields from the antenna radial current feed lines. The design, Fourier analysis, and measured impedances of the antennas used in PRETEXT are also presented. These antennas are coated with glass enamels and do not have Faraday shields. An upper limit on the plasma density behind the antenna was found with a microwave interferometer