Design and testing of 200 kW/91.2 MHz RF amplifier

A 1.5 MW ion cyclotron resonance heating (ICRH) system is being developed as an auxiliary heating system for steady state super-conducting tokamak-1 (SST-1) plasma. Different frequencies between 20 and 91.2 MHz have been selected to allow second harmonic and minority heating at 1.5 and 3.0 T toroidal magnetic fields. Various stages of amplifiers will be used to achieve the targeted power output at the above-mentioned frequencies. Two RF generator chains are being used to cover the desired operating frequencies. One is tunable from 20 to 45.6 MHz and the other one is fixed at 91.2 MHz with 2 MHz bandwidth. In the later chain of amplifiers a 20 kW amplifier is already tested at 91.2 MHz to drive the 200 kW stage of the amplifier. Based on tetrode an amplifier for output power of 200 kW is selected to avoid expected feedback problems at this power level. The design and testing procedure of 200 kW stage will be discussed in this paper.