42-GHz/500-kW Electron Cyclotron Resonance Heating System on Tokamak SST-1

The 42-GHz electron cyclotron resonance heating (ECRH) system on SST-1 is used to carry out ECRH-assisted preionization, breakdown, start-up, and heating experiments at 0.75-T (second harmonic) and 1.5-T (fundamental harmonic) operation. The gyrotron delivers 500-kW power at 42-GHz frequency at −50-kV beam voltage, 20-A beam current, and 19-kV anode voltage. The gyrotron has been commissioned successfully on dummy load for full parameters (500 kW/500 ms). The transmission line consists of matching optic unit, circular corrugated waveguide, miter bend with bidirectional coupler, waveguide switches, polarizer, bellows, dc breaks, and an uptaper. Approximately 20-m-long transmission line is used to launch the power from gyrotron to tokamak, and the burn pattern at the exit of line near the tokamak ensures a good Gaussian beam. A composite launcher [consisting of four mirrors (two profiled and two plane), two gate valves, and two vacuum barrier windows] is used to connect two ECRH systems (42 and 82.6 GHz). The 82.6-GHz/200-kW ECRH system is also planned for SST-1 to carry out experiments at 3-T magnetic field. The 42-GHz ECRH system has been commissioned with tokamak SST-1, ECRH power has been launched in tokamak, and successful ECRH-assisted breakdown is achieved at second harmonic.