Antennas for ICRF heating in the Alcator C-Mod tokamak

Abstract

The Alcator C-Mod tokamak experiment relies on ICRF heating as the sole source of auxilliary power. Two different antenna designs have been produced and fabricated for the ICRF heating experiments. The first antenna has a single current strap, a two-layer Faraday shield, and is movable radially. One of these antennas was built, conditioned to high RF voltage on a test stand, and installed on C-Mod for the first experimental run. The engineering goals of the first experiments include measuring the plasma loading and testing the power handling capability of the antenna. Details of the conditioning and tuning procedures will be presented. The second antenna has two phasable current straps and a single layer Faraday shield. The predicted high disruption forces require that it be attached securely to the vacuum vessel wall at a fixed radial position. Two of these antennas have been constructed, one having a titanium carbide coated Faraday shield and the other a boron carbide coated shield. They are designed to couple up to 4 MW of source power from two FMIT transmitters. Details of the fabrication and test stand conditioning of these antennas will be presented.