Pedestal confinement and stability in JET-ILW
Pedestal confinement and stability in JET-ILW
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JET-ILW 中的基座限制和稳定性
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发表时间：
2015
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通讯作者：
J. Contributors
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作者：
C. Maggi;S. Saarelma;F. Casson;C. Challis;E. L. Luna;L. Frassinetti;C. Giroud;E. Joffrin;J. Simpson;M. Beurskens;I. Chapman;J. Hobirk;M. Leyland;P. Lomas;C. Lowry;I. Nunes;F. Rimini;A. Sips;H. Urano;J. Contributors
2013-2014 年的新实验研究了 JET-ILW 运行初始阶段（2012 年实验活动）中观察到的 H 模式基座限制减少的物理原因。等离子体三角形、全局β和中性粒子对基座限制和稳定性的影响已经被系统地研究。在剥离-气球模型和基座预测代码 EPED 的模型假设的框架下分析了 JETILW 基座的稳定性。等离子体中的低 D 中性物含量（通过低 D2 气体注入速率或通过具有最佳泵送的偏滤器配置来实现）和高 beta 是良好基座（和核心）性能的必要条件。在这种情况下，基座稳定性与剥离-气球范式一致。 W 控制和 ILW 稳定 H 模式操作所需的中等到高 D2 气体速率会导致等离子体中 D 中性物质含量增加，并且可能需要基座模型中的额外物理原理来解释 ELM 不稳定性的发生。 H 模式性能的变化与 JET 壁成分从 C 到 Be/W 的变化相关，指向 D 中性粒子和低 Z 杂质，这些杂质在基座稳定性中发挥作用，这些元素目前未包含在基座模型中。需要解决这些方面的问题，以便实现基座高度的全面预测能力。
New experiments in 2013–2014 have investigated the physics responsible for the decrease in H-mode pedestal confinement observed in the initial phase of JET-ILW operation (2012 Experimental Campaigns). The effects of plasma triangularity, global beta and neutrals on pedestal confinement and stability have been investigated systematically. The stability of JETILW pedestals is analysed in the framework of the peeling–ballooning model and the model assumptions of the pedestal predictive code EPED. Low D neutrals content in the plasma, achieved either by low D2 gas injection rates or by divertor configurations with optimum pumping, and high beta are necessary conditions for good pedestal (and core) performance. In such conditions the pedestal stability is consistent with the peeling–ballooning paradigm. Moderate to high D2 gas rates, required for W control and stable H-mode operation with the ILW, lead to increased D neutrals content in the plasma and additional physics in the pedestal models may be required to explain the onset of the ELM instability. The changes in H-mode performance associated with the change in JET wall composition from C to Be/W point to D neutrals and low-Z impurities playing a role in pedestal stability, elements which are not currently included in pedestal models. These aspects need to be addressed in order to progress towards full predictive capability of the pedestal height.