A Resonant-Cavity ICRF Coupler for Large Tokamaks

A new resonant cavity ICRF coupler is proposed for large tokamaks. The design features a novel resonant cavity, an RF magneticfield orientation that effectively radiates fast Alfvén waves, matching to 40-Ω transmission lines, and an electric-field orientation so that the strongest RF electric fields are orthogonal to the main toroidal magnetic field, thereby benefiting from magnetic insulation. As a result, the power handling capability is excellent. For the case of the "Big-Dee" Doublet III tokamak, a single 35 × 50-cm coupler can launch 20 mW of fast Alfvén waves. Extrapolation to fusion reactor parameters is straightforward.