Design Status of the ITER Upper Port Launcher

The purpose of the ITER ECRH upper port antenna (or launcher) will be to drive current locally to stabilise the NTMs (depositing ECCD inside of the island which forms on the q=3/2 or 2 rational magnetic flux surfaces) and control the sawtooth instability (deposit ECCD near the q=1 surface). The launcher should be capable of steering the focused beam deposition location across the resonant flux surface over the range in which the q=1, 3/2 and 2 surfaces are expected to be found, for the various plasma equilibria susceptible to the onset of NTMs and sawteeth. ITER's present reference design uses a front steering (FS) concept, with the moveable mirror close to the plasma. Two separate mirrors are used to decouple the focussing and steering aspects resulting in an optimized optical configuration providing a well focused beam over a large steering range. The launcher is capable of steering eight 2MW beams in all of the four allocated upper port plugs. The critical component of the FS launcher is the steering mechanism, which will be a frictionless and backlash free mechanical system based on the compliant deformation of structural components to avoid the in vessel tribological difficulties. An inert gas pressure controlled bellows system provides accurate angular positioning of the steering mirror. The entire launcher (mm-wave components) can be designed fail-safe in that if a given subsystem fails, it can be isolated and ITER can continue operation. In addition, in-situ leak testing of critical components (steering mechanism, cooling, diamond window, etc.) is envisioned to insure proper functioning and avoidance of disrupting ITER operation. Details of the FS launcher design relating to physics performance, mm-wave optical design, thermohydraulic, electromagnetic and integration of launcher components into the port plug will be discussed.