ELM control strategies and tools: status and potential for ITER
ELM control strategies and tools: status and potential for ITER
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DOI：
10.1088/0029-5515/53/4/043004
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发表时间：
2013-03
期刊：
影响因子：
3.3
通讯作者：
P. Lang;A. Loarte;G. Saibene;L. Baylor;M. Becoulet;M. Cavinato;S. Clement-Lorenzo;E. Daly;
中科院分区：
文献类型：
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作者：
P. Lang;A. Loarte;G. Saibene;L. Baylor;M. Becoulet;M. Cavinato;S. Clement-Lorenzo;E. Daly;
在 Ip = 15 MA 和 QDT = 10 的设计值下，在参考感应场景中运行 ITER 需要实现良好的 H 模式限制，该限制依赖于边缘传输势垒的存在，而边缘传输势垒的基座压力高度是等离子体性能的关键。在这种情况下，边缘处会出现强梯度，从而驱动磁流体动力学不稳定性，从而产生边缘局域模式 (ELM)，从而导致从基座区域到面向等离子体的组件 (PFC) 的快速能量损失。如果没有适当的控制，ITER 中的 ELM 期间 PFC 上的热负载预计对于 Ip = 6–9 MA 的 H 模式运行变得非常重要；在较高等离子电流下运行会导致 PFC 的使用寿命大大缩短。目前，正在考虑几种方案来实现 ITER 中 ELM 控制所需的水平；这包括在自然没有或非常小的ELM的等离子体区域中运行，通过将其频率增加高达30倍来减少ELM能量损失，以及通过利用磁扰动主动控制边缘来避免ELM。通过影响边缘稳定性（通过等离子体成形、旋转剪切控制等）获得的小/无 ELM 状态在当前实验中表明，与 I 型 ELM 相比，ELM 热通量显着降低。然而，到目前为止，它们仅在有限范围的基座条件下被观察到，具体取决于每个特定的设备，并且它们对 ITER 的外推仍然不确定。通过增加频率进行的 ELM 控制依赖于导致 ELM 的边沿不稳定性的受控触发。目前已通过注射颗粒和等离子体垂直运动证明了这一点；颗粒提供了更有希望在 ITER 条件下应用的结果。 ELM 避免/抑制利用了这样一个事实：基座等离子体和磁场参数的相对较小的变化似乎对大型 ELM 具有很大的稳定作用。研究发现，应用非轴对称场的边缘磁场扰动会影响等离子体边缘的输运，从而防止等离子体压力梯度的失控上升和 I 型 ELM 的出现。本文对各种 ELM 控制方法进行了简要概述，总结了它们目前取得的成就，并简要讨论了它们在 ITER 中应用的悬而未决的问题。
Operating ITER in the reference inductive scenario at the design values of Ip = 15 MA and QDT = 10 requires the achievement of good H-mode confinement that relies on the presence of an edge transport barrier whose pedestal pressure height is key to plasma performance. Strong gradients occur at the edge in such conditions that can drive magnetohydrodynamic instabilities resulting in edge localized modes (ELMs), which produce a rapid energy loss from the pedestal region to the plasma facing components (PFC). Without appropriate control, the heat loads on PFCs during ELMs in ITER are expected to become significant for operation in H-mode at Ip = 6–9 MA; operation at higher plasma currents would result in a very reduced life time of the PFCs. Currently, several options are being considered for the achievement of the required level of ELM control in ITER; this includes operation in plasma regimes which naturally have no or very small ELMs, decreasing the ELM energy loss by increasing their frequency by a factor of up to 30 and avoidance of ELMs by actively controlling the edge with magnetic perturbations. Small/no ELM regimes obtained by influencing the edge stability (by plasma shaping, rotational shear control, etc) have shown in present experiments a significant reduction of the ELM heat fluxes compared to type-I ELMs. However, so far they have only been observed under a limited range of pedestal conditions depending on each specific device and their extrapolation to ITER remains uncertain. ELM control by increasing their frequency relies on the controlled triggering of the edge instability leading to the ELM. This has been presently demonstrated with the injection of pellets and with plasma vertical movements; pellets having provided the results more promising for application in ITER conditions. ELM avoidance/suppression takes advantage of the fact that relatively small changes in the pedestal plasma and magnetic field parameters seem to have a large stabilizing effect on large ELMs. Application of edge magnetic field perturbation with non-axisymmetric fields is found to affect transport at the plasma edge and thus prevent the uncontrolled rise of the plasma pressure gradients and the occurrence of type-I ELMs. This paper compiles a brief overview of various ELM control approaches, summarizes their present achievements and briefly discusses the open issues regarding their application in ITER.