Reflector antennas for electron cyclotron resonance heating of fusion plasma

For electron cyclotron resonance heating (ECH) of fusion plasma, transformation is required of the millimeter wave output from a gyrotron, circular TE/sub 0n/ mode, into a linearly polarized wave beam. It is easily realized by use of a parabolic cylinder reflector. Vlasov et al. proposed this type of reflector antenna which has a stair-cut aperture at an end of a circular waveguide. The authors recently proposed another type of antenna that also uses a parabolic cylinder and has an obliquely cut aperture. In this paper, the transformation efficiencies of polarization and radiation fields of the two types of antennas are calculated by means of geometrical optics and the Kirchhoff-Huygens principle. Then the authors propose a mode converter, in which the output of this type of parabolic reflector is led to a rectangular waveguide and transformed into TE/sub 10/ mode. In addition, another reflector antenna is proposed that focuses the wave beam using an elliptic cylinder reflector and a parabolic one.