Modelling eruptions and edge stability in tokamak plasmas
Modelling eruptions and edge stability in tokamak plasmas
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模拟托卡马克等离子体中的喷发和边缘稳定性
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发表时间：
2016
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通讯作者：
A. Lunniss
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作者：
A. Lunniss
在托卡马克运行的高约束模式(H模式)中，陡峭的梯度和托卡马克等离子体(基座)边缘附近产生的高自举电流通常会触发称为边缘局域模式(ELM)的喷发。在热核实验堆规模上，这些都有可能对材料造成不可接受的侵蚀。然而，存在不存在ELM的情况，例如静态H模式(QH)。ELITE代码最初是为了有效地计算托卡马克的边缘理想MHD稳定性而开发的，该托卡马克优化了与ELM相关的中高环模数n个模。在QH模式下，极限MHD通常为低n。第三章介绍了精英码对任意n的扩展。第四章给出了在低n下针对原始精英码以及GATO和MARG2D的成功基准测试。新精英码的第一个应用是研究DIII-D中QH模基座的稳定性。第五章给出了这项研究的结果，其中显示了低n现象的存在。
此外，了解JET-ITER类壁(ILW)等离子体中的基座性能损失对于未来JET和ITER实验的成功至关重要。第六章介绍了ELM间的基座稳定性研究，将基座的演化与基座结构模型EPED的准则进行了比较。这些结果表明，最大化具有第二次稳定通道的等离子体区域将导致最高的基座高度，从而获得最佳限制--这是优化JET和未来托卡马克(如ITER)的聚变性能的关键结果。
In the high confinement mode (H-mode) of tokamak operation, sharp gradients and the resulting high bootstrap current near the edge of a tokamak plasma (the pedestal) typically trigger eruptions called edge localised modes (ELMs). On the ITER scale, these have the potential to cause unacceptable erosion of materials. However, there exist scenarios, such as the quiescent H-mode (QH), where there are no ELMs. The ELITE code was originally developed to efficiently calculate the edge ideal MHD stability properties of tokamaks, optimised for the intermediate-high toroidal mode number, n, modes associated with ELMs. In QH-mode the limiting MHD is typically low n. Chapter 3 presents the extension of the ELITE code to arbitrary n. Chapter 4 presents successful benchmarks against the original ELITE code as well as GATO and MARG2D at low n. A first application of the new ELITE code was to study the stability of the QH-mode pedestal in DIII-D. Results from this study are presented in Chapter 5, which show the presence of low n phenomena.
Additionally, understanding the pedestal performance losses in JET ITER-like wall (ILW) plasmas is vital to the success of future JET and ITER experiments. Chapter 6 presents an inter-ELM pedestal stability study, which compares the pedestal evolution to the criteria of the pedestal structure model, EPED. These results suggest that maximising the region of plasma that has second stability access will lead to the highest pedestal heights and, therefore, best confinement - a key result for optimising the fusion performance of JET and future tokamaks, such as ITER.