Three-dimensional equilibrium reconstruction on the DIII-D device
Three-dimensional equilibrium reconstruction on the DIII-D device
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DOI：
10.1088/0029-5515/55/2/023009
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发表时间：
2015-01
期刊：
影响因子：
3.3
通讯作者：
S. Lazerson
中科院分区：
文献类型：
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作者：
S. Lazerson
诊断测量中环形变化的存在表明，当应用共振磁扰动 (RMP) 来抑制边缘局域模式时，托卡马克平衡的二维 (2D) 对称性可能会被破坏。虽然二维模型仍然可以实现托卡马克控制，但在进行详细分析时，会出现有关二维平衡的适用性的问题。特别是，有关边缘物理的问题将受益于平衡计算，该计算与指示环形变化的测量结果一致。对于仿星器和具有固有 3D 场结构的非轴对称设备来说，将三维 (3D) 平衡拟合到诊断测量的能力长期以来一直是一个挑战。 STELLOPT 代码通过将 3D VMEC 平衡拟合到磁、汤姆逊、动斯塔克效应 (MSE) 和电荷交换诊断中，为此类挑战提供了解决方案。使用 STELLOPT 重建应用 n = 3 RMP 的 DIII-D 托卡马克等离子体（发射号 142603）。重建由磁诊断拟合、测量的真空线圈电流、汤姆逊散射、电荷交换光谱和 MSE 偏振测定控制。重建的平衡具有压力梯度在低阶有理数下变得非常小的特征。这些特征可以与应用的 RMP 频谱相关联，指示该镜头的模式穿透。存在 0.5 cm 峰峰值量级的边界位移。这表明，虽然 3D 效应相对于等离子体小半径较小，但发生了共振模式穿透，表明 3D 重建能够解析等离子体中的小关键特征。
The presence of toroidal variation in diagnostic measurements indicates that the two-dimensional (2D) symmetry of tokamak equilibria can be violated when resonant magnetic perturbations (RMPs) are applied to suppress edge localized modes. While tokamak control is still possible with a 2D model, questions arise regarding the applicability of 2D equilibria when performing detailed analysis. In particular, questions regarding edge physics would benefit from equilibrium calculations which are consistent with measurements indicating toroidal variations. The ability to fit three-dimensional (3D) equilibria to diagnostic measurements has long been a challenge for stellarators, non-axisymmetric devices with an inherently 3D field structure. The STELLOPT code provides a solution to such a challenge by fitting 3D VMEC equilibria to magnetic, Thomson, motional Stark effect (MSE) and charge-exchange diagnostics. The plasma of the DIII-D tokamak with applied n = 3 RMP is reconstructed with STELLOPT (shot number 142603). The reconstruction is governed by fit to magnetic diagnostics, measured vacuum coil currents, Thomson scattering, charge-exchange spectroscopy and MSE polarimetry. The reconstructed equilibria possess features where pressure gradients become vanishingly small at low-order rationals. Such features can be associated with the applied RMP spectrum, indicating mode penetration for this shot. Boundary displacements on the order of 0.5 cm peak-to-peak were present. This suggests that while the 3D effect was small relative to the plasma minor radius, resonant mode penetration occurred, indicating the ability of 3D reconstructions to resolve small key features in the plasma.