A lower hybrid current drive system on the superconductive tokamak HT-7

A lower hybrid current drive system has been built for the HT-7 superconduc tive tokamak to deliver a 1.2-MW microwave at a frequency of 2.45 GHz for a pulse length of lip to 5 s. Twelve klystron amplifiers are used as wave ge nerators, each generating a 100-kW (130 kW at maximum) microwave. A grill c oupler composed of 2 x 12 waveguides is used to launch the waves from the 1 2 klystrons. The wave phase difference between the adjacent waveguides in e ither row of the grill can be set at ally desired value by feedback control ling the digital phase shifters in the low-power microwave circuits in fron t of the klystrons. The 12 klystrons are fed by two equal high-voltage powe r supplies. The technical reliability of the system is shown by experimenta l results.