Multi-channel vector generator system

The system described provides accurate and continuous analogue control of the phases and amplitudes of HF and microwave signals in multichannel systems for plasma heating in the Joint European Torus (JET) nuclear fusion experiment. Two RF systems are employed: one at 25-55 MHz couples energy into the plasma via the ions in its core (Ion Cyclotron Resonance Heating), and the 3.7 GHz Lower Hybrid Current Drive (LHCD) couples energy into the cooler outer regions of the plasma in order to broaden the temperature-radius profile. The LHCD system comprises 24 klystrons each feeding 700 kW to a multiport grille antenna in the reactor vessel. A travelling wavefront is generated across the grille by accurate phase modulation of each klystron output. Amplitude control is also provided and the whole system operates in a pulsed mode