ECH MW-level CW transmission line components suitable for ITER

The ECH transmission lines for ITER will require performance parameters not yet entirely demonstrated in ECH systems on present magnetic fusion energy machines. The key performance requirements for the main ITER transmission lines are operation at 1 MW for pulse lengths of 400–3600 s (essentially cw) at a frequency of 170 GHz. An additional consideration for transmission line performance is the possibility that ITER will use 2 MW coaxial cavity gyrotrons currently under development by Forschungszentrum Karlsruhe (FZK) and other European Associations and European tube industry. This paper addresses the progress made by General Atomics in the various transmission line components suitable for use on ITER. ITER design documents call for a corrugated waveguide inner diameter of 63.5 mm; many components have already been fabricated in this diameter, and those that have been made in other diameters (namely 31.75 and 88.9 mm) can readily be modified to a 63.5 mm i.d. design. In some cases, water-cooling must be added to present designs to remove heat deposited during cw operation of the components.