The measurement and correction of error fields in Wendelstein 7-X (W7-X) is critical to long pulse high beta operation, as small error fields may cause overloading of divertor plates in some configurations. Accordingly, as part of a broad collaborative effort, the detection and correction of error fields on the W7-X experiment has been performed using the trim coil system in conjunction with the flux surface mapping diagnostic and high resolution infrared camera. In the early commissioning phase of the experiment, the trim coils were used to open an n/m = 1/2 island chain in a specially designed magnetic configuration. The flux surfacing mapping diagnostic was then able to directly image the magnetic topology of the experiment, allowing the inference of a small ∼4 cm intrinsic island chain. The suspected main sources of the error field, slight misalignment and deformations of the superconducting coils, are then confirmed through experimental modeling using the detailed measurements of the coil positions. Observations of the limiters temperatures in module 5 shows a clear dependence of the limiter heat flux pattern as the perturbing fields are rotated. Plasma experiments without applied correcting fields show a significant asymmetry in neutral pressure (centered in module 4) and light emission (visible, H-alpha, CII, and CIII). Such pressure asymmetry is associated with plasma-wall (limiter) interaction asymmetries between the modules. Application of trim coil fields with n = 1 waveform correct the imbalance. Confirmation of the error fields allows the assessment of magnetic fields which resonate with the n/m = 5/5 island chain.
Wendelstein 7-X（W7-X）中误差场的测量与校正在长脉冲高β运行中至关重要，因为即使很小的误差场也可能在某些位形下导致偏滤器靶板过载。因此，作为一项广泛合作努力的一部分，在W7-X装置上利用trim线圈系统，结合磁面测绘诊断和高分辨率红外相机，开展了误差场的探测与校正实验。在装置早期调试阶段，通过trim线圈在一种专门设计的磁位形中打开了一个n/m = 1/2的岛链。随后，磁面测绘诊断能够直接成像该磁拓扑结构，从而推断出存在一个约4 cm的内禀岛。通过利用线圈位置的详细测量数据进行实验验证，确认了误差场的主要来源可能是超导线圈的轻微错位和变形。对限制器温度的观测显示，在模块5中，限制器热流图案随扰动场的旋转而呈现明显的依赖性。在未施加校正场的情况下，等离子体表现出显著的中性气压不对称性（集中在模块4）以及可见光、H-alpha、CII和CIII辐射的不对称性。这种气压不对称性与模块间等离子体-壁（限制器）相互作用的不对称性相关。施加具有n = 1波形的trim线圈场可校正该不平衡。误差场的确认使得能够评估与n/m = 5/5岛链共振的磁场。