Upgrading and operating of the 80 MHz transmitter on the Alcator C-MOD tokamak

ICRF heating experiments in the Alcator C-MOD tokamak rely on FMIT transmitters as the power source. The first phase of experiments will require up to 4 MW from two FMIT units. In contrast to other projects, C-MOD is the only tokamak experiment where the original 80 MHz fixed frequency cavities have been retained. The first unit is operational and the required 2 MW, 1 sec. pulses have been run into a dummy load using both an EIMAC X2242 and X2274 for the final power amplifier. During operation of the experiment, access to the transmitters will not be possible. All control and monitoring is done remotely, using a PLC with PC interface. Data acquisition during a shot is done through CAMAC. Fast arc detection circuitry has been developed to protect the transmitter and other RF components. Details of the modification and operation of the transmitters will be presented. Future plans call for upgrading the system by adding additional units and extending the pulse length to 10 sec. A companion paper describes the Alcator ICRF antennas