Collisional scattering effects on the quasilinear dynamics of Alfvénic eigenmodes

The interaction between fast ions and Alfvénic eigenmodes has proved to be numerically expensive to be modeled in realistic tokamak configurations. Therefore it can be convenient to exploit reduced modeling for simulations where the simultaneous excitation of multiple unstable Alfvénic instabilities is expected. The Resonance Broadening Quasilinear (RBQ) code, which is capable of modeling the fast ion distribution function while self-consistently evolving the amplitude of modes, is presently under development. RBQ is interfaced with linear ideal/kinetic codes, NOVA/NOVA-K, which provide eigenstructures, damping rates and wave-particle interaction matrices for resonances in the constant of motion space. We report recent progress on the development and verification of the diffusion solver used in the RBQ code by comparing numerical outputs with known analytical solutions. Both the wave-particle resonant diffusion and Coulomb collisional scattering diffusion operator are thoroughly verified. In addition, we report detailed analyses of the collisional scattering frequency dependence of the modes saturation level.