Design of ICRF antennas for TFTR

Abstract

Two 4-MW ICRF (ion cyclotron range of frequencies) antennas have been designed for the Tokamak Fusion Test Reactor (TFTR). The antennas will be installed adjacent to the two existing antennas, bringing the maximum ICRF heating capacity to 12.5 MW. The design goals were to increase the loading to the plasma, to reduce the tendency for arcing, and to simplify the fabrication and assembly of the device. The antenna, consisting of an RF cavity with slots at the front end (facing the plasma), utilizes a center-mounted spline drive mechanism for positioning the device with respect to the plasma edge and for resisting the forces generated during disruptions. The Faraday shields are unique for each launcher, though they share common design elements. Both launchers use solid Inconel rods that are bent to a radius matching the plasma and tilted six degrees in order to be parallel with the combined poloidal and toroidal fields of the tokamak. The 'Bay K' launcher uses a single row shield while the 'Bay N' launcher incorporates a double row shield. Faraday shield protection and the center-grounded current straps are also discussed.<>