The maximum stable pedestal pressure has been shown to increase with core pressure and, in combination with core transport effects, this can lead to a positive feedback mechanism. However, the effect is shown to saturate for a high β in ASDEX-Upgrade simulations [Wolfrum et al. “Impact of wall materials and seeding gases on the pedestal and on core plasma performance,” Nucl. Mater. Energy 12, 18 (2017)]. In this paper, it is numerically investigated whether this effect appears in ITER plasmas, using ideal MHD numerical codes HELENA and MISHKA for different ITER scenarios, in a range of plasma conditions: two inductive scenarios at 7.5 MA/2.65 T and 15 MA/5.3 T and one steady-state scenario at 10 MA/5.3 T. For all scenarios, reference cases for ITER plasmas were taken as a starting point. No pedestal pressure saturation is found for the inductive scenarios, gradually growing up to the global βN limit, which is determined by the Troyon limit. On the contrary, for the 10 MA/5.3 T steady-state scenario, the maximum stable pedestal pressure does not depend on the total β and it is limited by low-n kink-peeling modes, as opposed to high-n peeling-ballooning modes that limit the maximum attainable pedestal height in the inductive scenarios. This core-edge MHD stability feedback loop has been investigated for two assumptions regarding the scaling of the pedestal width with β p , ped ¯, using either a constant pedestal width or when scaling it as Δ ψ N ∝ β p , ped ¯ 1 / 2. A stronger core-edge MHD stability feedback is observed for the varying pedestal width for the inductive plasma scenarios, which is closer to the experimental results from JET [Challis et al. “Improved confinement in JET high plasmas with an ITER-like wall,” Nucl. Fusion 55(5), 053031 (2015)], but not for the steady-state one. Finally, the pressure achieved according to this core-edge feedback stability analysis is compared to the plasma pressure achievable on the basis of the energy confinement IPB98(y,2) scaling for various assumptions regarding the scaling of core plasma confinement with heating power.

中文翻译：

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评估核心 Beta 对 ITER 中基座 MHD 稳定性的影响以及对能量限制的影响

最大稳定基座压力已被证明会随着核心压力的增加而增加，并且结合核心传输效应，这可以导致正反馈机制。然而，在 ASDEX-Upgrade 模拟中，高 β 的效果显示出饱和 [Wolfrum 等人。“壁材料和引种气体对基座和核心等离子体性能的影响，”Nucl。母校。能源 12, 18 (2017)]。在本文中，在一系列等离子体条件下，使用理想的 MHD 数值代码 HELENA 和 MISHKA 对 ITER 等离子体中是否出现这种效应进行了数值研究：7.5 MA/2.65 T 和 15 MA/5.3 的两种感应情况T 和一个 10 MA/5.3 T 的稳态情景。对于所有情景，ITER 等离子体的参考案例都被作为起点。对于感应场景，没有发现基座压力饱和，逐渐增长到全局 βN 极限，这是由 Troyon 极限确定的。相反，对于 10 MA/5.3 T 稳态情况，最大稳定基座压力不取决于总 β 并且受低 n 扭结剥离模式的限制，与高 n 剥离膨胀相反在感应场景中限制最大可达到的基座高度的模式。这个核心边缘 MHD 稳定性反馈回路已经研究了关于基座宽度与 β p 缩放的两个假设，ped ¯，使用恒定的基座宽度或将其缩放为 Δ ψ N ∝ β p , ped ¯ 1 / 2. 对于感应等离子体场景的不同基座宽度，观察到更强的核心边缘 MHD 稳定性反馈，这更接近 JET 的实验结果 [Challis 等人。“通过类似 ITER 的壁改进了 JET 高等离子体中的限制，”Nucl。Fusion 55(5), 053031 (2015)]，但不适用于稳态。最后，将根据该核心边缘反馈稳定性分析获得的压力与基于能量限制 IPB98(y,2) 比例可实现的等离子体压力进行比较，该比例针对有关核心等离子体限制与加热功率缩放的各种假设。