It is demonstrated that finite-pressure, approximately quasi-axisymmetric stellarator equilibria can be directly constructed (without numerical optimization) via perturbations of given axisymmetric equilibria. The size of such perturbations is measured in two ways, via the fractional external rotation and, alternatively, via the relative magnetic field strength, i.e. the average size of the perturbed magnetic field, divided by the unperturbed field strength. It is found that significant fractional external rotational transform can be generated by quasi-axisymmetric perturbations, with a similar value of the relative field strength, despite the fact that the former scales more weakly with the perturbation size. High mode number perturbations are identified as a candidate for generating such transform with local current distributions. Implications for the development of a general non-perturbative solver for optimal stellarator equilibria are discussed.

中文翻译：

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扰动轴对称磁平衡以获得准轴对称仿星器

已经证明，通过给定轴对称平衡的扰动，可以直接构建（无需数值优化）有限压力、近似准轴对称的仿星器平衡。这种扰动的大小以两种方式测量，通过分数外旋转，或者通过相对磁场强度，即扰动磁场的平均大小除以未扰动场强。研究发现，准轴对称扰动可以产生显着的分数外部旋转变换，具有相似的相对场强值，尽管前者随扰动大小的比例更弱。高模数扰动被识别为用于生成具有局部电流分布的这种变换的候选。