Inter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamak
Inter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamak
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ASDEX 升级托卡马克边缘电流密度分布的 Inter-ELM 演化
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发表时间：
2014
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通讯作者：
M. Dunne
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作者：
M. Dunne
由于边缘局域模式(ELMS)，托卡马克第一壁上的等离子体存储能量突然减少和随后的能量沉积可能会对未来聚变堆的成功造成不利影响。了解和控制ELM对于延长这些设备的寿命以及最大化其性能至关重要。普遍接受的ELMS图像假定等离子体边缘存在一个临界压力梯度和电流密度，超过该临界压力梯度和电流密度，耦合磁流体流动力剥离-气球模式将变得不稳定。近年来，人们对边缘压力梯度的时空演变进行了大量的分析。然而，由于测量边沿电流密度的困难，通常忽略了边沿电流密度。在本论文中，提出了一种新的电流密度恢复方法，利用ASDEX升级托卡马克上测量的外磁和内边缘动力学数据，使用平衡求解器CLISTE来重建高分辨率平衡。给出了边缘电流密度相对于ELM碰撞的演化，表明电流密度积累的阻性延迟是不可能的。不确定度分析表明，边缘电流密度的测定精度与所用动力学数据一致。与新古典主义理论的比较表明，CLISTE测得的电流密度与计算的分布符合得很好。研究了三种榆树缓解机制：II型榆树、受外部磁场扰动的榆树和氮种榆树。在前两种情况下，发现电流密度随着时间的推移而减小，这表明等离子体行为更像气球。在后一种情况下，磁通表面平均电流密度会降低，而局部电流密度会增加，从而提供了一种抑制剥离和气泡模式的机制。
The sudden decrease of plasma stored energy and subsequent power deposition on the first wall of a tokamak due to edge localised modes (ELMs) is potentially detrimental to the success of a future fusion reactor. Understanding and control of ELMs is critical for the longevity of these devices and also to maximise their performance. The commonly accepted picture of ELMs posits a critical pressure gradient and current density in the plasma edge, above which coupled magnetohy drodynamic peeling-ballooning modes become unstable. Much analysis has been presented in recent years on the spatial and temporal evolution of the edge pressure gradient. However, the edge current density has typically been overlooked due to the difficulties in measuring this quantity. In this thesis, a novel method of current density recovery is presented, using the equilibrium solver CLISTE to reconstruct a high resolution equilibrium utilising both external magnetic and internal edge kinetic data measured on the ASDEX Upgrade tokamak. The evolution of the edge current density relative to an ELM crash is presented, showing that a resistive delay in the buildup of the current density is unlikely. An uncertainty analysis shows that the edge current density can be determined with an accuracy consistent with that of the kinetic data used. A comparison with neoclassical theory demonstrates excellent agreement be- tween the current density determined by CLISTE and the calculated profiles. Three ELM mitigation regimes are investigated: Type-II ELMs, ELMs sup- pressed by external magnetic perturbations, and Nitrogen seeded ELMs. In the first two cases, the current density is found to decrease as mitigation on- sets, indicating a more ballooning-like plasma behaviour. In the latter case, the flux surface averaged current density can decrease while the local current density increases, providing a mechanism to suppress both the peeling and ballooning modes.
M.MURAKAMI：“AFT 中约束的无量纲缩放”等离子体物理和受控核聚变研究 1992 年。（1993 年）
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