Speaker
Description
Nonaxisymmetric magnetic perturbations in tokamaks play an important role in determining plasma rotation by generating neoclassical toroidal viscous (NTV) torque [1]. Such threedimensional magnetic perturbations arise from a variety of external and internal sources, including resonant magnetic perturbation (RMP) coils, intrinsic error fields, and magnetohydrodynamic (MHD) activity. Since sufficient plasma rotation is essential for plasma stability, precise modeling of NTV is necessary for present-day as well as future reactors.
Several established approaches for NTV modeling exist, including continuum drift-kinetic
solvers like NEO-2 [2] and resonant models like NEO-RT [1] and GPEC/PENTRC [3]. A common assumption underlying these models is that the radial width of particle orbits is small
compared to the characteristic width of the applied magnetic perturbation. However, since this
requirement is not always satisfied, further investigation of the effect of finite particle orbits is
necessary for reliable NTV predictions. Recent developments in the code NEO-RT now also include finite orbits as well as different orbit classes, such as "potato" orbits close to the magnetic
axis [4].
In this work, established NTV models are first benchmarked for the ASDEX Upgrade tokamak. Subsequently, the impact of finite orbit effects on the calculated NTV torque is investigated
in detail. In particular, the radial distribution of the produced NTV torque is analyzed, providing
insight into how finite orbits modify NTV torque in the presence of three-dimensional magnetic
perturbations.