Anode modulator power supplies for continuous duty 500 kW klystrons (TH2103D) & 200 kW gyrotron (VGA8000A19)

Initial testing and commissioning of two high power klystrons (TH2103D) and gyrotron (VGA8000A19) have been carried out at our Institute. Each of the klystrons is capable of delivering 500 kW at 3.7 GHz, to be used for non-inductive lower hybrid current drive (LHCD) in the Steady State Superconducting Tokamak (SST-1). The gyrotron is capable of delivering 200 KW at 28 GHz, for breakdown and electron cyclotron resonant heating (ECRH) experiments on Aditya tokamak. The potential appearing at the anode point with respect to the cathode will turn-ON, turn-OFF and control the beam current. Thus these anode modulator power supplies control the out put power of the devices. Main input for both the power supplies is derived from the cathode power supply. A -2 kV bias power supply is connected between the modulator output and anode terminal to suppress dark current. The output pulse duration is adjustable from 50 msec. to 1000 sec. by the control system. The oil cooled tetrode YU155 is used as shunt voltage regulator in the klystron anode modulator power supply. A potential divider is made with the tetrode as a series element. It operates in its linear range and a variable voltage is available at the klystron anode by varying the impedance of the tetrode.