Development and Fabrication of Steady State Fast Wave Antenna for LHD

The ICRF antenna for LHD has been developed and tested in a test stand. All parts of the antenna system was originally designed to stand for the high voltage and the high heat load from the plasma and the RF dissipation loss during long operation time. In the test stand the R&D antenna consisting of these parts is tested for the steady state operation of 30 minutes at the antenna current of 800 A successfully. Ceramic feedthroughs of several types were newly designed and tested for the RF voltage of above 40 kV in steady state. These results are incorporated in the design and fabrication of the real plasma heating antenna of LHD. A pair of the fast wave antennas for LHD is fabricated. These antennas are the largest ones for the helical device and are also the first trial device to carry out the really steady state heating of above 1 MW. The launcher section is designed to fit the plasma surfaces and the magnetic field of LHD. The swing motion of the antenna can change its position to control the plasma coupling and the heat load. The heat load of the steady state operation is the serious problem' The ANSYS heat conduction calculation of the carbon protectors shows the antenna position control is very effective to reduce the heat load of the protectors.