A CUTOFF WAVE-GUIDE APERTURE ANTENNA WITH FARADAY SHIELD

Basic characteristics of a cutoff waveguide aperture antenna used for large scale ICRF (ion cyclotron range of frequency) plasma heating are investigated. Main interests axe focused on the effects of the Faraday shield covering the aperture surface. The analysis is performed for the antennas radiating into semi-infinite vacuum space rather than a magnetoplasma to understand the basic characteristics of the antenna where the loading effect due to the presence of the plasma is excluded. Theoretical results show that the input admittance of the aperture antenna with the Faraday shield is similar to that without the shield qualitatively. On the other hand the aperture electric field distribution is quite different for these two cases. The validity of the anisotropic boundary condition which has been often used to incorporate the effects of the Faraday shield is also discussed. In order to confirm the validity of the analysis, experimental results of the input admittance and aperture field are presented.