Orbit-averaged quasilinear diffusion operator in the ion-cyclotron range of frequencies

The absorption of radio-frequency waves in the ion-cyclotron range of frequencies (ICRF) in fusion plasmas is adequately described in the frame of the quasilinear theory. A peculiarity of ICRF heating is to increase the fraction of trapped particles, whose the guiding-center trajectories are typically banana orbits with finite width. One possible way to properly account for the effects due to the finite-width orbits is provided by the orbit-averaged quasilinear theory. Here, we propose a routine for the evaluation of the orbit-averaged quasilinear diffusion tensor, given the the wave fields from the full wave code TORIC. Particular care is taken in the evaluation of the contribution of each wave-particle resonance as well as for the transition between the two regimes of correlated and uncorrelated resonances along the orbit. We discuss the quasilinear diffusion coefficient thus obtained and validate the result by comparing the power deposition profile computed from the orbit-averaged quasilinear operator with the one determined by TORIC. For future applications, a novel algorithm for the calculation of the corresponding Monte Carlo operators is also presented.