An intermediate power amplifier upgrade for 40 to 80 Mhz for the alcator C-Mod ICRF transmitters

Abstract

ICRF operations with Alcator C-Mod consists of 4 transmitters, of which two are tunable within the 40 MHz to 80 MHz band. These transmitters were comprised of 3 stages all of which employed vacuum tube amplifiers. As a part of the general plan to upgrade the two tunable transmitters, a project was implemented to replace the first stage, the intermediate power amplifier, with a 10 kilowatt solid state broadband amplifier. There were two primary benefits from the upgrade. The tuning of the transmitters was considerably simplified and better performance was obtained under a variety of operational conditions by having a conservative power margin. The improvements obtained are an important first step toward advancing the overall radio frequency performance of the transmitters and minimizing the time intensive task of changing the frequency of operation.