The On-Axis Magnetic Well and Mercier's Criterion for Arbitrary Stellarator Geometries

低-n Mercier不稳定Wendelstein仿星器与托卡马克中准交换模式的比较

A comparison of low-n Mercier unstable Wendelstein stellarators and quasi-interchange modes in tokamaks

本研究比较了Mercier不稳定Wendelstein仿星器与托卡马克准交换模式的非线性演化，通过模拟W7-X型位形和W7-AS实验重构，探讨了超越Mercier稳定性极限的机制与设计可能性。

Magnetic well and Mercier stability of stellarators near the magnetic axis

We have recently demonstrated that by expanding in small distance from the magnetic axis compared to the major radius, stellarator shapes with low neoclassical transport can be generated efficiently. To extend the utility of this new design approach, here we evaluate measures of magnetohydrodynamic interchange stability within the same expansion. In particular, we evaluate magnetic well, Mercier's criterion, and resistive interchange stability near a magnetic axis of arbitrary shape. In contrast to previous work on interchange stability near the magnetic axis, which used an expansion of the fl…

Non-planar elasticae as optimal curves for the magnetic axis of stellarators

The problem of finding an optimal curve for the target magnetic axis of a stellarator is addressed. Euler-Lagrange equations are derived for finite length three-dimensional curves that extremise their bending energy while yielding fixed integrated torsion. The obvious translational and rotational symmetry is exploited to express solutions in a preferred cylindrical coordinate system in terms of elliptic Jacobi functions. These solution curves, which, up to similarity transformations, depend on three dimensionless parameters, do not necessarily close. Two closure conditions are obtained for the…

Fluid simulations of plasma filaments in stellarator geometries with BSTING

Here we present first results simulating plasma filaments in non-axisymmetric geometries, using a fluid turbulence extension of the \boutxx~framework. This is made possible by the implementation of the Flux Coordinate Independent scheme for parallel derivatives, an extension of the metric tensor components which allows them to vary in three dimensions, and development of grid generation. Tests have been performed to confirm that the extension to three dimensional metric tensors does not compromise the accuracy and stability of the associated numerical operators. Recent changes to the FCI grid …

SCR-1 仿星器物理特性表征：探究等离子体放电、MHD平衡计算及O-X-B模式转换可行性

Characterization of the SCR-1 Stellarator Physics: Investigating Plasma Discharge, MHD Equilibrium Calculations, and O-X-B Mode Conversion Feasibility

本研究探究了SCR-1仿星器的等离子体放电特性，利用VMEC代码计算MHD平衡并分析线性稳定性，同时使用IPF-FMDC全波代码验证了电子伯恩斯坦波O-X-B模式转换的可行性，发现O-X转换率最高达63%。

Residual zonal flows in tokamaks and stellarators at arbitrary wavelengths

In the linear collisionless limit, a zonal potential perturbation in a toroidal plasma relaxes, in general, to a non-zero residual value. Expressions for the residual value in tokamak and stellarator geometries, and for arbitrary wavelengths, are derived. These expressions involve averages over the lowest order particle trajectories, that typically cannot be evaluated analytically. In this work, an efficient numerical method for the evaluation of such expressions is reported. It is shown that this method is faster than direct gyrokinetic simulations performed with the GENE and EUTERPE codes. C…