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A 8 GHz, high power, microwave system for the heating of thermonuclear plasmas

The Frascati Tokamak Upgrade (FTU) is a machine included in the European Thermonuclear Fusion Program aimed at investigating high density plasmas in presence of powerful additional RP heating systems. The Lower Hybrid Resonant Heating (LHRH) system, based on 9 independent modules, works at 8 GHz, and will generate, at full performances, a total amount of 9 MW, in pulsed regime (pulse length = 1 s, duty cycle = 1/600). The microwave power source is a gyrotron oscillator, developed by Thomson Tubes Electroniques (France) for this specific application, able to produce up to 1 MW. An overmoded, low loss, circular waveguide transmits the RF power toward the plasma; an array of 12 × 4 rectangular waveguides (the "grill") launches this power into the plasma. The paper describes the LHRH system for FTU and analyses both its main performances and experimental results.