# Quasilinear diffusion coefficients in a finite Larmor radius expansion for ion cyclotron heated plasmas

## TL;DR

This paper derives a simplified quasilinear diffusion model for ion cyclotron range of frequency waves in tokamaks, ensuring key properties of the full model and validating it through ITER scenario simulations.

## Contribution

It introduces a finite Larmor radius expansion-based reduced model for quasilinear diffusion, coupling Maxwell's equations and the Fokker-Planck equation self-consistently.

## Key findings

- The reduced model accurately reproduces full model results within error margins.
- Implementation in the TORIC-CQL3D code enables efficient simulations.
- Validation through ITER minority heating scenario confirms model reliability.

## Abstract

In this paper, a reduced model of quasilinear diffusion by a small Larmor radius approximation is derived to couple the Maxwell's equations and the Fokker-Planck equation self-consistently for ion cyclotron range of frequency waves in a tokamak. The reduced model ensures the important properties of the full model by Kennel-Engelmann diffusion, such as diffusion directions, wave polarizations, and H-theorem. The kinetic energy change (W-dot) is used to derive the reduced model diffusion coefficients for the fundamental damping and the second harmonic damping to the lowest order of the finite Larmor radius expansion. The quasilinear diffusion coefficients are implemented in a coupled code (TORIC-CQL3D) with the equivalent reduced model of dielectric tensor. We also present the simulations of the ITER minority heating scenario, in which the reduced model is verified within the allowable errors from the full model results.