Resonant ion diffusion in ICRF-heated Tokamak plasmas

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Abstract
Wave-induced particle transport during ion cyclotron heating in Tokamak plasmas is studied. Diffusion takes place both in real and velocity space. The real space diffusion occurs due to absorption of the waves' toroidal angular momentum. This process can lead to a pump-out of resonating ions in regions with large power densities giving rise to hollow density profiles, lower energy of the heated ions, flattening of the profile of power transfer to the background ion species and toroidal acceleration of the plasma. The transport in real and velocity space is studied by reducing the problem to a time-dependent 2-D diffusion problem, 1-D in velocity space and 1-D in real space. This is done by using various models for the distribution in pitch angle. The resulting 2-D diffusion problem is then solved numerically.