Hard magnetohydrodynamic limit in 1/3 sawtooth like activity in LHD
Hard magnetohydrodynamic limit in 1/3 sawtooth like activity in LHD
复制标题
LHD 中 1/3 锯齿状活动的硬磁流体动力学极限
DOI：
10.1063/1.4867066
复制
发表时间：
2014
影响因子：
2.2
通讯作者：
S. Ohdachi and Y. Narushima
中科院分区：
文献类型：
--
作者：
J. Varela;K. Y. Watanabe;S. Ohdachi and Y. Narushima
LHD内移位形放电的优化是一个悬而未决的问题。这些弛豫事件限制了驱动周期性等离子体解除约束的LHD性能。本研究的目的是分析具有不同稳定性的等离子体中的锯齿状活性，以预测最佳操作条件，并将其不良影响降至最低。我们总结了几个MHD模拟的结果与Lundquist数之间的等离子体在慢重联制度，研究平衡的性质，在链的发病期间的类磁事件。研究结果指出，强共振类磁事件发生后，等离子体内部区域可达到硬磁流体极限，并触发等离子体坍缩。如果系统保持在软MHD极限，即在一个政权的压力梯度和磁湍流低于临界值，以驱动软-硬MHD过渡，崩溃可以避免。在软MHD极限下，系统弛豫是非共振类磁事件或共振类磁事件的弱形式。在软磁流体力学制度的系统弛豫驱动一个小的等离子体解除约束，不限制LHD的性能，如果事件的周期性不是很高。
The optimization of LHD discharges in inward-shifted configurations withsawtooth like activity is an open issue. These relaxation events limit the LHD performance driving a periodic plasma deconfinement. The aim of this study is to analyze thesawtooth like activity in plasmas with different stability properties to foreseen the best operation conditions and minimize its undesired effects. We summarize the results of several MHD simulations for plasmas with Lundquist numbers betweenandin the slow reconnection regime, studying the equilibria properties during the onset of a chain ofsawtooth like events. The research conclusions point out that the hard MHD limit can be reached in the inner plasma region after the onset of a strongresonant sawtooth like event and trigger a plasma collapse. The collapse can be avoided if the system remains in the soft MHD limit, namely in a regime with a pressure gradient and a magnetic turbulence below the critical values to drive the soft-hard MHD transition. In the soft MHD limit the system relaxations are the non resonantsawtooth like events or a weak version of theresonant sawtooth like events. A system relaxation in the soft MHD regime drives a minor plasma deconfinement that doesn't limit the LHD performance if the event periodicity is not very high.