The Alcator C-Mod lower hybrid current drive experiment low power microwave and active control system

A 3 MW (upgradeable to 4 MW) 4.6 GHz Lower Hybrid Current Drive (LHCD) system is being implemented on Alcator C-Mod to control and sustain current profile evolution. The LHCD low-power microwave and active control system, using fast vector modulators, will provide a phase and amplitude controlled driver for each of twelve 4.6 GHz, 250 kW klystrons. Resulting phase and power outputs of each klystron will be monitored by I-Q detectors and made available for closed-loop control of the klystron phase and amplitude during plasma shots. Synchronized digital controllers will be implemented for each control loop and operation will be coordinated with external fast protection circuitry provided in the LHCD transmitter and coupler protection systems.