Fast-magnetosonic-wave heating of the conceptual NUWMAK tokamak reactor

Studies of radiofrequency (RF) coupling and heating to ignition of a conceptual tokamak fusion reactor by means of the fast magnetosonic wave at the first ion cyclotron harmonic (ω=2ωsub(ci)) are presented. First, the current status of fast magnetosonic wave propagation and heating is briefly reviewed. Next, a spatially averaged, time-dependent start-up model is used to describe the role of RF heating for ignition of a tokamak reactor. The model shows that 240MJ corresponding to an RF power level of 80MW for a three-second period is quite sufficient to ignite a 700MW(e) fusion power plant the size of NUWMAK. To couple the RF power to the torus, both external cavities coupled by apertures and poloidal coil systems are considered. Wave coupling from an external vacuum-filled cavity to fast magnetosonic waves via apertures provides matching through an impedance transformation from a co-axial feed to the plasma wave modes. (author)