Recent advancements in the design of the LHCD system for ITER

The overall configuration of the LHCD system for ITER has been substantially outlined during the EDA phase. A following first detailed study has been performed in the frame of ITER tasks and contracts. In the actual configuration the proposed system has a working frequency of 5 GHz and couples to the plasma an overall RF power of 20 MW through a launcher based on the passive active multijunction (PAM) concept. Specific microwave components couple the output rectangular waveguides of the RF sources to the circular waveguides, excited in the low losses, TE°₀₁ mode, of the main transmission line (MTL) and to split it again in rectangular waveguides, at the end of this line, to adequately feed the PAM launcher. Selective TE°₀₁ mode filters are included in the MTL to eliminate unwanted modes that could be accidentally originated in the discontinuities of this line, such as the 90° bends used to follow the optimized path between the RF sources and the launcher. Ceramic windows (BeO) separate the launcher, at the same pressure of the vacuum vessel of ITER, from the MTL. Most of these components have been recently revised and have been object of a more accurate analysis. In same cases alternative components have been ascertained and studied. The paper gives the actual status of the system.