Design of the final power amplifier stage for the 30 MHz TFTR FMIT RF sources

Two of the 80 MHz transmitters originally built for the Fusion Materials Irradiation Test facility (FMIT) by Continental Electronics Manufacturing Company were converted by PPPL RF Engineering to operate at 30 MHz in the TFTR ICRF System. This system consists of six multimegawatt RF sources providing radio frequency power to antennas located at four bays on TFTR. Power levels of more than two megawatts have been supplied by each of these sources at pulse widths of three seconds. This paper presents the detailed design and analyses of the Final Power Amplifier (FPA) stage of these new sources and its subsequent fabrication and commissioning. The FPA utilizes re-entrant cavities similar in design to those used in the Intermediate Power Amplifier and Driver stages. A brief description of the sources´ setup to accommodate impedance variations of plasma-loaded antennas is also included. Finally, an overview of the ICRF tube protection system is discussed