Effects of bootstrap current on magnetic configuration in Chinese first quasi-axisymmetric stellarator

Nuclear Fushion

article

Haifeng Liu¹  Jian Zhang¹  Yuhong Xu¹  Akihiro Shimizu²  Wilfred Anthony Cooper⁴  Shoichi Okamura²  Mitsutaka Isobe²  Xianqu Wang¹  Jie Huang¹  Jun Cheng¹  Hai Liu¹  Xin Zhang¹  Changjian Tang¹ 

[1] Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University;National Institute for Fusion Science, National Institutes of Natural Sciences;The Graduate University for Advanced Studies;Swiss Alps Fusion Energy

关键词: quasi-axisymmetric stellarator;    bootstrap current;    MHD stabilities;    neoclassical transport;    micro-instability;   

DOI  :  10.1088/1741-4326/acadef

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Neoclassical properties in quasi-axisymmetric (QA) stellarators are analogous to these in tokamaks. Consequently, a substantial bootstrap current could significantly modify the MHD equilibrium properties of a QA stellarator, which is an important characteristic in this type of stellarator. This paper is dedicated to systemically investigate the effects of bootstrap current on the magnetic configuration in Chinese first quasi-axisymmetric stellarator (CFQS). For the first time, self-consistent bootstrap currents in free-boundary equilibria are calculated with an accurate Fokker–Planck neoclassical numerical mode in CFQS. Several important results are achieved: (a) as the bootstrap current grows with increasing volume-averaged normalized pressure beta , magnetic shear develops in the bulk plasma and meanwhile, a deep magnetic well is robustly sustained, which leads to improved stabilization of interchange modes up to beta sim 2.0{{% }} . (b) In the analysis of global ideal MHD instability, as the bootstrap current rises to 39 kA (beta sim 1.3{{% }} ), external kink modes become destabilized and the unstable mode withm / n= 2/1 is dominant. (c) From beta = 0to 1.5%, the bootstrap current hardly changes the QA property and a low neoclassical transport is maintained. However, as betais enhanced beyond 2.0%, the substantial bootstrap current gives rise to an increase of non-QA magnetic field components, which weakens the neoclassical transport properties. (d) An increase of the negative magnetic shear at the core region by the bootstrap currents has a favorable effect on the properties ofJ(second adiabatic invariant). The maximum- Jregion can be extended by raising bootstrap currents.

【 授权许可】

Unknown