Abstract
We present a new formulation for quasilinear velocity space diffusion for ICRF plasmas that considers two different aspects: (1) finite Larmor radius approximation and (2) includes the effect of toroidal geometry and constructs a positive definite form. In the first aspect, the Kennel-Engelmann (K-E) quasilinear diffusion coefficients are successfully approximated in a small Larmor radius limit and implemented for the numerical codes (TORIC-CQL3D). In the second aspect, the quasilinear diffusion is reformulated in a toroidal geometry in order to include the parallel dynamics in the inhomogeneous plasmas and magnetic fields. We use these two quasilinear formulations to simulate ITER plasmas with ICRF injection for minority fundamental heating and Tritium second harmonic cyclotron heating.
Highlights
The ion cyclotron range of frequency (ICRF) waves transfer their energy and momentum to plasmas, and as a result a significant amount of fast ions are produced
The quasilinear diffusion coefficients are derived by Kennel and Engelmann (K-E) [1] with the assumptions of the homogenous plasmas and magnetic fields along the particle trajectory
The coefficients are modified to be consistent with the dielectric tensor of the reduced model in the small Larmor radius approximation
Summary
The ion cyclotron range of frequency (ICRF) waves transfer their energy and momentum to plasmas, and as a result a significant amount of fast ions are produced. The coefficients are modified to be consistent with the dielectric tensor of the reduced model in the small Larmor radius approximation. As the result of the self-consistency, the power absorptions by dielectric tensor and quasilinear diffusion theoretically match each other and the numerical iterations between the Maxwell’s equation solver and the Fokker-Planck code likely converge without any normalization factor to the diffusion coefficients [4]. Using this new positive-definite from, we can eliminate the unphysical growing mode violating H-theorem and the related numerical errors in the coupled code TORICCQL3D. To best of our knowledge, it is the first implementation of the positive-definite form for the quasilinear diffusion coefficient in a continuum FokkerPlanck solver for a toroidal geometry
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