Open AccessThe three-dimensional equilibrium with magnetic islands and MHD instabilities in the CFQS quasi-axisymmetric stellarator
Author(s) -
Xianqu Wang,
Yuhong Xu,
A. Shimizu,
M. Isobe,
S. Okamura,
Y. Todo,
H. Wang,
H. Liu,
Jie Huang,
X. Zhang,
Hai Liu,
J. Cheng,
C. J. Tang
Publication year - 2021
Publication title -
nuclear fusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.774
H-Index - 120
eISSN - 1741-4326
pISSN - 0029-5515
DOI - 10.1088/1741-4326/abd3ec
Subject(s) - magnetohydrodynamics , magnetohydrodynamic drive , physics , stellarator , plasma , magnetic field , ballooning , mechanics , beta (programming language) , rational surface , rotational symmetry , instability , condensed matter physics , tokamak , nuclear physics , quantum mechanics , computer science , programming language
The equilibrium of the Chinese first quasi-axisymmetric stellarator (CFQS) has been investigated by the HINT code. It is found that the stochastization of magnetic field lines expands with the increase in the volume-averaged beta value 〈 β 〉 in the plasma boundary. In the high- β regime, the generation of large magnetic islands at rational surfaces not only leads to an effective shrinkage of the plasma confinement region but also increases the outward shift of the magnetic axis. With bootstrap current effects, the low-order islands spread over the whole plasma area, leading to a stochastization of magnetic field lines due to island chain overlapping. However, for a flat pressure profile, the magnetic islands are significantly suppressed so that the magnetic surfaces can be fairly maintained. Moreover, the magnetohydrodynamic (MHD) instabilities in the optimized CFQS configurations have been simulated by the MEGA code. The linear properties of unstable resistive MHD modes are studied. The results show that in the CFQS the main MHD behaviour is dominated by the resistive ballooning modes with strong mode coupling. The mode structure and resistivity scaling are consistent with related theories.