arXiv subjects

Dirk Van Eester

Publications and source records attributed to Dirk Van Eester.

3 recordsLinked to original sources

arXiv2026

Towards solving the ICRH wave and Fokker-Planck equations self-consistently

The present paper sketches a framework for solving the wave and Fokker-Planck equations in the ion cyclotron resonance frequency domain fully selfconsistently. It illustrates this can be done by first constructing "building blocks" that are commonly needed by the wave and Fokker-Planck equations, allowing e.g. to account for wave coupling in plasmas containing non-Maxwellian distributions. Up to details, the paper exploits known expressions and methods to solve the two intimately connected aspects of the description of the wave-particle interaction underlying ion cyclotron resonance heating. Two cases are presented: the case where the guiding centre motion is limited to just following magnetic field lines, and the extended case accounting for drifts away from magnetic surfaces but assuming axisymmetry. A limited set of analytical results is included. As combining wave and Fokker-Planck solving is the focus, the computation of the dielectric response for arbitrary distribution functions is illustrated as well.

physics.plasm-ph↗

arXiv2023

Semi-analytical derivation of the 2D all-FLR ICRH wave equation as a high-order partial differential equation

For 1-dimensional applications, Bude's method [Bude et al, Plasma Phys. Control. Fusion, 63 (2021) 035014] has been shown to be capable of accurately solving the all-FLR (Finite Larmor Radius) integro-differential wave equation as a high-order differential equation allowing to represent all physically relevant (fast, slow and Bernstein) modes upon making a polynomial fit that is accurate in the relevant part of k-space. The adopted fit is superior to the Taylor series expansion traditionally adopted to truncate the series of finite Larmor radius corrections, while the differential rather than integro-differential approach allows for significant gain in required computational time when solving the wave equation. The method was originally proposed and successfully tested in 1D for radio frequency (RF) waves and in absence of the poloidal field [D. Van Eester & E. Lerche, Nucl. Fusion, 61 (2021) 016024]. In the present paper, the derivation of the extension of that procedure to 2D and for finite poloidal field - semi-analytically yielding the coefficients of the relevant high-order partial differential equation - is discussed in preparation of future numerical application.

physics.plasm-ph↗

arXiv2014

Kinetic description of wave induced plasma flow in the radio frequency domain

A model for ICRH induced flows in the presence of a strong magnetic field is presented. These flows are the finite temperature counterpart of flows existing in cold plasmas described e.g. in [D. Van Eester et al., Plasma Phys. Control. Fusion 55 (2013) 025002] and thus do not rely on the waves being damped. The kinetic corrections offer insight in what happens at cyclotron resonances. Authors commonly either rely on the confining magnetic field $\vec{B}_o$-field to be strong, or the electric field $\vec{E}$-field to be rapidly varying but are not accounting for both when writing down the solution of the equation of motion on the slow time scale. In this paper, the equation of motion is solved for constant $B_o$ to keep the discussion as simple as possible. The simultaneous presence of $\vec{B}_o$ and the $\vec{E}$-field inhomogeneity causes drifts perpendicular to the $\vec{B}_o$ and to other slow time scale accelerations, the Ponderomotive acceleration being one of them. Because of the first and having tokamak applications in mind, these flows - although small in magnitude - cause drifts that enter in competition with transport induced flows.

physics.plasm-ph↗