MAST血浆平衡的证据交叉验证和贝叶斯推断
Evidence Cross-Validation and Bayesian Inference of MAST Plasma Equilibria
摘要：
本文根据拾取线圈、磁通环和运动斯塔克效应（MSE）观测数据，采用贝叶斯统计理论，直接计算了MAST等离子体放电电流分布。通过将环形等离子体电流表示为一系列具有矩形横截面的轴对称电流束并推断这些束中的每一个的电流，随后通过比奥-萨伐尔定律的基本应用计算通量表面几何形状和q-分布。在贝叶斯分析的背景下使用这种等离子体模型是由Svensson和Werner在联合欧洲托卡马克（JET）上开创的[J. Svensson和A。沃纳轴对称等离子体的电流层析成像。{ \em等离子体物理和受控聚变}，50（8）：085002，2008]。在这个框架中，线性前向模型被用来生成诊断预测，随后通过应用贝叶斯公式直接计算等离子体束集合中的电流的概率分布。在这项工作中，我们引入了一种新的诊断技术，以识别和删除异常值的观察与诊断脱落的校准或遭受不明故障。这些修改使得最后闭合通量面（LCFS）的贝叶斯推断与其他确证数据（例如使用EFIT++ [L. Appel等人，第33届EPS会议，意大利罗马，2006年]。此外，这种分析也产生错误的等离子体电流分布和通量表面的几何形状，以及直接预测的Shafranov移动的等离子体核心。
英文摘要：
In this paper, current profiles for plasma discharges on the Mega-Ampere Spherical Tokamak (MAST) are directly calculated from pickup coil, flux loop and Motional-Stark Effect (MSE) observations via methods based in the statistical theory of Bayesian analysis. By representing toroidal plasma current as a series of axisymmetric current beams with rectangular cross-section and inferring the current for each one of these beams, flux-surface geometry and q-profiles are subsequently calculated by elementary application of Biot-Savart's law. The use of this plasma model in the context of Bayesian analysis was pioneered by Svensson and Werner on the Joint-European Tokamak (JET) [J. Svensson and A. Werner. Current tomography for axisymmetric plasmas. {\em Plasma Physics and Controlled Fusion}, 50(8):085002, 2008]. In this framework, linear forward models are used to generate diagnostic predictions, and the probability distribution for the currents in the collection of plasma beams was subsequently calculated directly via application of Bayes' formula. In this work, we introduce a new diagnostic technique to identify and remove outlier observations associated with diagnostics falling out of calibration or suffering from an unidentified malfunction. These modifications enable good agreement between Bayesian inference of the last closed flux-surface (LCFS) with other corroborating data, such as such as that from force balance considerations using EFIT++ [L. Appel et al., Proc. 33rd EPS Conf., Rome, Italy, 2006]. In addition, this analysis also yields errors on the plasma current profile and flux-surface geometry, as well as directly predicting the Shafranov shift of the plasma core.
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