AI 中文总结
该研究利用DIII-D的L-H转换数据库，评估3D磁场对H模式功率阈值及0-D经验回归稳定性的影响，发现实测阈值功率有偏差，经验估计低估快离子损失，添加3D场度量效果不佳，特定条件等限制0-D标度预测能力，改进预测需更好处理快离子损失和相关物理量。
AI 中文摘要
利用DIII-D中192次L-H转换的数据库来评估施加的三维（3D）磁场对H模式功率阈值和零维（0-D）经验回归稳定性的影响。数据集包括名义上轴对称的放电以及具有共振或非共振磁扰动的放电。通过滤波标准减少与吸收功率、中性束调制和快离子损失相关的不确定性，同时使用平衡重建和光谱分析对施加场分量进行量化。测量的阈值功率显示出与2008年ITPA多机标度有很大的散射和系统偏差。TRANSP建模表明经验估计可能会严重低估快离子损失。添加全局3D场度量不能可靠地分离施加扰动的影响。完全无约束的回归保留了70%的残余均方根误差并产生非物理参数依赖性。这些结果表明隐藏变量依赖性会强烈影响经验阈值参数化。特定机器条件、局部边缘物理和功率核算不确定性限制了纯0-D标度的预测能力。对ITER和未来设备的改进预测需要更好地处理快离子损失和基于物理的边缘局部量。
英文摘要
A database of 192 L-H transitions in DIII-D is used to assess the effects of applied three-dimensional (3D) magnetic fields on the H-mode power threshold and the stability of zero-dimensional (0-D) empirical regressions. The dataset includes nominally axisymmetric discharges and discharges with resonant or non-resonant magnetic perturbations. Filtering criteria reduce uncertainties associated with absorbed power, neutral-beam modulation, and fast-ion losses, while applied-field components are quantified using equilibrium reconstruction and spectral analysis. Measured threshold powers show substantial scatter and systematic deviations from the 2008 ITPA multi-machine scaling, including for discharges without applied perturbations. TRANSP modeling indicates that empirical estimates can substantially underpredict fast-ion losses, particularly at low plasma current and with non-axisymmetric fields. Adding global 3D-field metrics does not robustly isolate the effects of applied perturbations. A fully unconstrained regression retains a 70% residual root-mean-square error and produces nonphysical parameter dependencies, including a plasma surface-area exponent of 2.79. Extrapolations to ITER-relevant conditions consequently have broad confidence intervals. These results show that hidden-variable dependencies can strongly affect empirical threshold parameterizations even in a restricted single-machine dataset. Machine-specific conditions, local edge physics, and power-accounting uncertainties limit the predictive capability of purely 0-D scalings. Improved predictions for ITER and future devices will require better fast-ion-loss treatment and physics-based, edge-localized quantities.
