SIMULATION OF THE EXCITATION OF COAXIAL MODES BY AN ICRH ANTENNA ON A LABORATORY MODEL.

This paper reports results of measurements on a laboratory model of coaxial geometry in which the excitation of coaxial modes by a conventional strip-line ICRH antenna is studied. It is experimentally shown that the electrostatic shield is very effective in suppressing the axisymmetric (or TEM) coaxial modes. The use of side limiters around the unshielded antenna or its placement in a wall indentation decreases the TEM coaxial radiation in agreement with theoretical expectations.