The aim of the ITER electron cyclotron heating and current drive upper launcher (UL) is to control magnetohydrodynamic activity in the plasma, in particular neoclassical tearing modes, requiring a narrow and peaked deposition of the radio-frequency (rf) power. The millimeter-wave (mm-wave) system of the UL is optimized to ensure that the eight rf beams are all focused to a small beam width at the resonance location. The present design uses two mitre bends per beam and a focusing mirror for each set of four beams, orientating each set onto a single steering mirror (SM) to inject it into the plasma. The SM is rotated using a frictionless and backlash free pneumo-mechanical system. A first prototype of the SM has been constructed to demonstrate the manufacturability and the actuation principle and to develop an adequate control strategy. A test program has been developed to ensure the integrity of the launcher from the pre-build-to-print design phase (research and development) up to the tests after maintenance. This paper presents a general overview of the system, a description of the progress in the mm-wave optical layout, low-power tests, alignment specifications of the mm-wave components, and SM capabilities to meet the ITER requirements.
|Journal||Fusion Science and Technology|
|Publication status||Published - 2009|