Jiang Y Z, Tan Y, Gao Z, Nakamura K, Liu W B, Wang S Z, Zhong H, Wang B B
Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
Research Institute for Applied Mechanics, Kyushu University, 8168580 Kasuga, Japan.
Rev Sci Instrum. 2017 Sep;88(9):093510. doi: 10.1063/1.5002190.
Accurate mutual inductances between magnetic diagnostics and poloidal field coils are an essential requirement for determining the poloidal flux for plasma equilibrium reconstruction. The mutual inductance calibration of the flux loops and magnetic probes requires time-varying coil currents, which also simultaneously drive eddy currents in electrically conducting structures. The eddy current-induced field appearing in the magnetic measurements can substantially increase the calibration error in the model if the eddy currents are neglected. In this paper, an expression of the magnetic diagnostic response to the coil currents is used to calibrate the mutual inductances, estimate the conductor time constant, and predict the eddy currents response. It is found that the eddy current effects in magnetic signals can be well-explained by the eddy current response determination. A set of experiments using a specially shaped saddle coil diagnostic are conducted to measure the SUNIST-like eddy current response and to examine the accuracy of this method. In shots that include plasmas, this approach can more accurately determine the plasma-related response in the magnetic signals by eliminating the field due to the eddy currents produced by the external field.
磁诊断与极向场线圈之间精确的互感是确定用于等离子体平衡重建的极向通量的基本要求。通量线圈和磁探针的互感校准需要随时间变化的线圈电流，这同时也会在导电结构中驱动涡电流。如果忽略涡电流，磁测量中出现的涡电流感应场会大幅增加模型中的校准误差。在本文中，利用磁诊断对线圈电流的响应表达式来校准互感、估计导体时间常数并预测涡电流响应。结果发现，通过涡电流响应确定可以很好地解释磁信号中的涡电流效应。进行了一组使用特殊形状鞍形线圈诊断的实验，以测量类SUNIST涡电流响应并检验该方法的准确性。在包含等离子体的放电中，这种方法可以通过消除外部场产生的涡电流所引起的场，更准确地确定磁信号中与等离子体相关的响应。
