An equilibrium validation technique based on Bayesian inference
An equilibrium validation technique based on Bayesian inference
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DOI：
10.1088/0029-5515/51/10/103005
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发表时间：
2011-10
期刊：
影响因子：
3.3
通讯作者：
M. Hole;G. V. von Nessi;J. Svensson;L. Appel
中科院分区：
文献类型：
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作者：
M. Hole;G. V. von Nessi;J. Svensson;L. Appel
近年来，贝叶斯概率理论已被用于许多实验，以消除诊断数据和正演模型中的不确定性和相互依赖性，并与等离子体状态的先验知识相结合，从而提高推断物理变量的准确性。主要进展包括在电流和磁通表面层析成像、有效电荷、电子能量分布函数、中子能谱和密度方面的应用。还引入了虚拟观测，以更好地约束当前层析成像中的推测量。在这项工作中，我们给出了环向电流和极向电流以及磁通表面层析成像的贝叶斯推断结果。虽然这些分布中的不确定性以及推断参数(如安全系数分布)中的不确定性很小(<；5%)，但根据所使用的物理模型，推断可能会发生很大变化。我们还给出了汤姆逊散射和电荷交换复合光谱的贝叶斯推断结果。在单独的工作中，我们计算了Mega Ampére球形托卡马克中面上的径向力平衡分量。我们的目标是为不同的平衡物理模型建立一个验证框架。我们发现，在磁芯(归一化极向通量小于0.4)和运动斯塔克效应(MSE)弦的重叠区，等离子体在两个标准偏差内符合静态Grad-Shafrov力平衡。在外侧边缘区域，也可以获得MSE数据，压力梯度超过洛伦兹力。最有可能的是，这是因为极向电流在等离子体边缘不被限制为零。最基本的是，结果表明，力平衡的计算组件对于评估数据一致性是有用的，而不依赖于任何平衡解决方案。对于第一阶，我们将余量积分到力平衡，从而推断出高能粒子压强。
In recent years, Bayesian probability theory has been used in a number of experiments to fold uncertainties and interdependences in the diagnostic data and forward models, and together with prior knowledge of the state of the plasma, thus increase accuracy of inferred physics variables. Key developments include the application to current and flux surface tomography, effective charge, the electron energy distribution function, neutron spectrometry and density. Virtual observations have also been introduced to better constrain inferred quantities in current tomography. In this work we present Bayesian inference results of toroidal and poloidal current and flux surface tomography. Whilst the uncertainty in these profiles, as well as the uncertainty in inferred parameters such as the safety factor profile is small (<5%), the inference can change substantially depending on the physics model used. We also present Bayesian inference results for Thomson scattering and charge-exchange recombination spectroscopy. In separate work we have computed radial force balance components on the midplane in the Mega Ampére Spherical tokamak. Our aim is to establish a validation framework for different equilibrium physics models. We find that in the overlapping region of the core (normalized poloidal flux less than 0.4) and motional Stark effect (MSE) chords, the plasma is consistent with static Grad–Shafranov force balance to within two standard deviations. In the outboard edge region, where MSE data are also available, the pressure gradient exceeds the Lorentz force. Most likely, this is because the poloidal current is not constrained to zero at the plasma edge. To lowest order, the results suggest computing components of force balance are useful to assess data-consistency, independent of any equilibrium solution. To first order, we have integrated the residue to force balance to infer an energetic particle pressure.