Development of fast steerable launcher for ECRH system

•A new ECRH launcher has been developed for the ECRH system capable of steering EC beam in poloidal and toroidal directions.•The poloidal steering is fast and can be done in real time during the plasma discharge.•UHV compatibility and the motion characteristics of the launcher has been tested in a specially designed vacuum chamber. Electron cyclotron resonance heating (ECRH) launcher is an electro-mechanical system mainly consisting of mirrors (flat and profiled), a steering mechanism, a vacuum barrier window and a UHV (Ultra High Vacuum) compatible gate valve which focuses and steers the ECRH beam into plasma. Presently, Steady-state Superconducting Tokamak (SST)-1 ECRH system has a 42 GHz Gyrotron capable of delivering 500 kW of RF power for the maximum duration of 500 ms. A new steerable ECRH launcher has been developed which can steer the EC beam along both poloidal and toroidal directions. The span of mirror movement in poloidal and toroidal directions is ±20° and ±50°, respectively. The poloidal motion of the mirror can be done in real-time during plasma operation and the mirror can be rotated by 20° in 100 ms. Two AC servo motors independently control the mirror movements through an assembly of motion feedthroughs, spur gears and mechanical linkages. The accuracy, repeatability and speed of both the motions have been measured under UHV in a specially designed vacuum chamber.