TFTR ICRF generator systems

The design and performance of the Tokamak Fusion Test Reactor (TFTR) ion cyclotron range of frequencies (ICRF) generators and the overall RF system which controls multiple sources to provide 10 MW of ICRF power to the TFTR are discussed. Two 3.0-MW amplifiers operating at 47 MHz were designed and built. Their design is discussed in detail. Two 2.0-MW amplifiers tunable over the 40 MHz to 80 MHz range were designed to upgrade systems originally built for use on the Fusion Materials Irradiation Test Facility (FMIT). Design details of these systems are shown along with the characteristics of an experimental tetrode vacuum tube, designated the X-2242, developed for these systems. Operation of several high-power RF sources into single or coupled antennas in the TFTR vacuum vessel requires tight phase and amplitude control of each source to achieve an impedance match to the plasma. The method of controlling the amplifiers using phase-locked loops and amplitude feedback loops around each amplifier system is shown in detailed block diagram form. Final performance characteristics for the amplifiers operating singly and in combination into dummy loads are presented. Several problems peculiar to tokamak plasma loads are discussed in regard to their effect on the design and performance of the high-power RF amplifiers