A study of a dataset of JET H-mode plasma with the Be/W ITER-like wall (JET-ILW) shows that reaching the edge MHD ballooning limit leads to confinement degradation. However, unlike JET plasmas with a carbon wall (JET-C), the JET-ILW plasmas stay in a marginal dithering phase for a relatively long period, associated with a higher (≈20%) H-mode density limit (HDL) than JET-C equivalents. This suggests that ITER could be operated in H-mode with higher density than the scaling based on carbon wall devices, but likely with a dithering phase plasma with lower confinement. A new, reliable estimator for JET E _r,min has been derived by combining HRTS measurements of pedestal gradient and edge-SOL decay lengths. JET radial E _r ETB wells are observed in the range of −15 to −60 kV m⁻¹ in high performance H-modes, consistent with previous CXRS results in ASDEX Upgrade. The results imply that a higher positive E B shear in the near SOL plays a role in sustaining a marginal phase in JET-ILW which leads to a higher HDL than that in JET-C. The results of the JET-ILW dataset show agreement with the Goldston finite collisionality HD model for SOL broadening at high collisionality. A hypothesis for the dithering H-mode phase is proposed: as n _e,SOL increases, ν _∗,SOL increases, SOL broadens, E _r shear decreases, triggers L-mode; n _e drops, ν _∗,SOL decreases, SOL becomes narrower, and E _r shear increases, triggering H-mode, resulting in a cycle of H–L–H- oscillations. For burning plasma devices, such as ITER, operating just below the MHD limit for the dithering phase could be a promising regime for maximising core density, and fusion performance while minimising plasma-material interaction. The oscillatory signal during the dithering phase could be used as a precursor of undesirable plasma performance for control purposes.

对具有类 Be/W ITER 壁 (JET-ILW) 的 JET H 模式等离子体数据集的研究表明，达到边缘 MHD 膨胀极限会导致约束退化。然而，与具有碳壁的 JET 等离子体 (JET-C) 不同，JET-ILW 等离子体在相对较长的时间内停留在边缘抖动阶段，与更高 (≈20%) 的 H 模式密度限制 (HDL) 相关。 JET-C 等价物。这表明，与基于碳壁装置的缩放相比，ITER 可以在 H 模式下以更高的密度运行，但可能使用具有较低限制的抖动相位等离子体。通过结合基座梯度和边缘 SOL 衰减长度的 HRTS 测量，推导出了一种新的、可靠的 JET E _r,min估计器。JET 径向E _r在高性能 H 模式下，在-15 至 -60 kV m ^-1范围内观察到 ETB 井，这与之前 ASDEX 升级中的 CXRS 结果一致。结果表明，在近 SOL 中较高的正E B剪切在维持 JET-ILW 的边缘阶段中起作用，这导致比 JET-C 中的 HDL 更高。JET-ILW 数据集的结果表明与 Goldston 有限碰撞 HD 模型一致，用于在高碰撞时 SOL 展宽。提出了抖动 H 模式相位的假设：随着n _e,SOL增加，ν _*,SOL增加，SOL 变宽，E _r剪切减小，触发 L 模式；n _e滴，ν _*，SOL下降，SOL变得更窄，并且Ë _ř剪切增加时，触发H模式，产生H-L-H-振荡的周期。对于燃烧等离子体装置，例如 ITER，在抖动阶段的 MHD 限制以下运行可能是最大化核心密度和聚变性能同时最小化等离子体材料相互作用的有希望的机制。抖动阶段期间的振荡信号可用作用于控制目的的不希望的等离子体性能的前体。