Work

Effects of zero and reversed magnetic shear on resistive wall modes in a straight limiter tokamak with zero beta

Year: 2024

Type: article

Abstract: Advanced tokamak scenarios often feature equilibriums with zero and reversed magnetic shear. To isolate and investigate their impacts on the resistive wall mode (RWM) instability analytically, we construct a series of cylindrical limiter equilibriums with different magnetic shear in the core and toward plasma edge, as a prototype of the configurations in advanced tokamak scenarios. Equilibriums with zero β are considered so that the analysis focuses on the current-driven RWMs. Analytical solutions for the n=1 resistive wall mode, derived from the reduced ideal magnetohydrodynamics (MHD) equations, consistently demonstrate key insights for both the core and the edge: the growth rate of RWMs is inversely proportional to the averaged magnetic shear when the safety factor at the edge (qa) is held constant. Specifically, an increase in positive averaged magnetic shear results in a decreased growth rate, whereas an increase in negative averaged magnetic shear leads to an increased growth rate. Furthermore, the influence of nqa on the mode's stability significantly surpasses the effects of magnetic shear changes previously discussed. These analytical calculation results provide a verification of NIMROD simulations.

Source: Physics of Plasmas

DOI: 10.1063/5.0234675

Authors: Sui Wan, Ping Zhu, Haolong Li

Institutions: Huazhong University of Science and Technology, University of Wisconsin–Madison, Shenzhen University

Language: English

Topic: Magnetic confinement fusion research

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Funders: U.S. Department of Energy, National Natural Science Foundation of China, National Magnetic Confinement Fusion Program of China

Awards: G418306698, G7217562219, NONLINEAR AND NONIDEAL MHD