MAST固有误差场的测量、修正及其意义
Measurement, correction and implications of the intrinsic error fields on MAST
摘要：
托卡马克中磁场线圈的不对准会导致磁场的环向不对称，这被称为固有误差场。这些误差场通常导致等离子体中形成锁定模式，这限制了可实现的最低密度。MAST上的固有误差场已经通过直接测量来自这些线圈的场的环形不对称性来确定，并且已经根据线圈的失真来参数化。使用误差场校正线圈来校正误差场，其中通过确定确保放电离锁定模式的开始最远所需的电流来找到最佳校正。这些经验得出的校正与已知的线圈失真进行了比较。在真空近似中，预测的和经验确定的校正之间存在~ 3的差异。当包括等离子体响应时，获得更好的一致性，但仍有一些情况下，一致性不好，这表明其他影响，如误差场与等离子体的非线性耦合是重要的。
英文摘要：
The misalignment of field coils in tokamaks can lead to toroidal asymmetries in the magnetic field, which are known as intrinsic error fields. These error fields often lead to the formation of locked modes in the plasma, which limit the lowest density that is achievable. The intrinsic error fields on MAST have been determined by the direct measurement of the toroidal asymmetry of the fields from these coils and have been parameterised in terms of distortions to the coils. The error fields are corrected using error field correction coils, where the optimum correction is found by determining the current required to ensure that the discharge is furthest from the onset of a locked mode. These empirically derived corrections have been compared with the known coil distortions. In the vacuum approximation there is a factor of ~ 3 difference between the predicted and empirically determined correction. When the plasma response is included better agreement is obtained, but there are still some cases where the agreement is not good, which suggests that other effects such as the non-linear coupling of the error field to the plasma are important.
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