SCATTERING OF FUSION PRODUCTS AND MAGNETIC RECONNECTION IN IGNITING PLASMAS; DEVELOPMENTS IN THE IGNITOR PROGRAM

摘要

In collisionless regimes, the effects of finite electron inertia are shown to be inadequate for the development of modes that require magnetic reconnection for their excitation. Instead, modes resulting from an underlying state of microscopic turbulence are proposed to explain the coherent m = 4, n = 3 and m = 3, n = 2 activity which has been observed in D and D-T experiments with vigorous neutral beam injection carried out by the TFTR machine. These modes have the characteristics necessary (i.e. a phase velocity in the direction of the ion diamagnetic velocity, the appropriate frequency and spatial localization) to produce resonant scattering of the high energy nuclei that are injected or produced by fusion reactions. In fact, modes of this kind may have a beneficial role in removing fusion products from the center of the plasma column as they slow down to the characteristic resonance energy. The main parameters of the Ignitor experiment are presented, and the completion of the construction of the key machine components is described, validating its technological feasibility. The Ignitor strategy of reaching ignition by minimizing the auxiliary heating, recently adopted by the ITER design, is illustrated. The unique possibility that Ignitor has to remain within the ideal MHD stability bounds while reaching ignition is emphasized. The experiment is also well suited for the investigation of advanced plasma regimes, including the study of long time-scale processes, access to the second stability region and the production of significant power by D-~3He fusion reactions with confinement of the 14.7 MeV fusion protons.