Theory of Equivalent Tokamaks for Characterizing Turbulent Transport in Quasi-symmetric Stellarators
Abstract
It is well known that quasi-symmetric (QS) stellarators are isomorphic to tokamaks in terms of their neoclassical-transport properties, and the corresponding transport coefficients can be calculated in the same manner as in tokamaks. However, less is known regarding the turbulent-transport properties of QS stellarators, e.g. the transport coefficients from the ion-temperature-gradient (ITG) mode. In this work, a systematic theory of the ``equivalent tokamaks'' for QS stellarators is presented based on the local gyrokinetic formulation and the near-axis expansion theory. It is shown that to zeroth order in the minor radius, the equivalent tokamaks can be chosen to have circular flux surfaces and can be characterized by three geometric quantities: the aspect ratio, the rotational transform, and the magnetic shear. To achieve first-order accuracy, however, not all QS stellarators have equivalent tokamaks, but good approximations can be found for some cases either as global or local equilibria. Local and global gyrokinetic simulations of ITG transport are performed for a selection of QS configurations, and quantitative agreement in the turbulent transport levels is found between the stellarators and their equivalent tokamaks.
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BibTeX
@misc{zhu2026theory,
title = {{Theory of Equivalent Tokamaks for Characterizing Turbulent Transport in Quasi-symmetric Stellarators}},
author = {Hongxuan Zhu and R. Gaur and X. Wei and Z. Lin and A. Bhattacharjee},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01131},
eprint = {2610.01131},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01131},
}
RIS
TY - UNPB
TI - Theory of Equivalent Tokamaks for Characterizing Turbulent Transport in Quasi-symmetric Stellarators
AU - Hongxuan Zhu
AU - R. Gaur
AU - X. Wei
AU - Z. Lin
AU - A. Bhattacharjee
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.01131
UR - https://arxiv.org/abs/2610.01131
AB - It is well known that quasi-symmetric (QS) stellarators are isomorphic to tokamaks in terms of their neoclassical-transport properties, and the corresponding transport coefficients can be calculated in the same manner as in tokamaks. However, less is known regarding the turbulent-transport properties of QS stellarators, e.g. the transport coefficients from the ion-temperature-gradient (ITG) mode. In this work, a systematic theory of the ``equivalent tokamaks'' for QS stellarators is presented based on the local gyrokinetic formulation and the near-axis expansion theory. It is shown that to zeroth order in the minor radius, the equivalent tokamaks can be chosen to have circular flux surfaces and can be characterized by three geometric quantities: the aspect ratio, the rotational transform, and the magnetic shear. To achieve first-order accuracy, however, not all QS stellarators have equivalent tokamaks, but good approximations can be found for some cases either as global or local equilibria. Local and global gyrokinetic simulations of ITG transport are performed for a selection of QS configurations, and quantitative agreement in the turbulent transport levels is found between the stellarators and their equivalent tokamaks.
ER -