The tokamak density limit: A thermo-resistive disruption mechanism
The tokamak density limit: A thermo-resistive disruption mechanism
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DOI：
10.1063/1.4922472
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发表时间：
2015-06
影响因子：
2.2
通讯作者：
D. Gates;D. Brennan;L. Delgado-Aparicio;R. White
中科院分区：
文献类型：
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作者：
D. Gates;D. Brennan;L. Delgado-Aparicio;R. White
研究了磁岛在三维电子温度下的行为，以及相应的三维电阻率对磁岛生长的影响。我们把由此产生的一类非线性称为热阻效应。特别地，不同杂质混合对先前提出的局部岛发病阈值的影响[Gates和Delgado-Aparicio， Phys]。Rev. Lett. 108, 165004(2012)]被检查并显示与密度极限下托卡马克的良好实验标度一致。一个令人惊讶的简单的半解析理论被开发出来，它强加了在岛屿内部加热/冷却的影响以及岛屿几何形状的影响。对于所考虑的这类电流剖面，发现在修正的卢瑟福方程中需要一个新的项来解释岛不对称的热效应。所得到的模型显示出一个快速增长的撕裂模式的稳健开始-与在托卡马克密度极限下观察到的破坏机制一致。进行了完全非线性的三维圆柱计算，通过提高/抑制岛核心的温度来模拟净岛加热/冷却的效果。在解析理论和数值模拟中，发现快速生长的突然阈值是由于影响岛电阻率的三个不同的热非线性之间的相互作用，从而改变了生长动力学。
The behavior of magnetic islands with 3D electron temperature and the corresponding 3D resistivity effects on growth are examined for islands with near-zero net heating in the island interior. We refer to the resulting class of non-linearities as thermo-resistive effects. In particular, the effects of varying impurity mix on the previously proposed local island onset threshold [Gates and Delgado-Aparicio, Phys. Rev. Lett. 108, 165004 (2012)] are examined and shown to be consistent with the well established experimental scalings for tokamaks at the density limit. A surprisingly simple semi-analytic theory is developed which imposes the effects of heating/cooling in the island interior as well as the effects of island geometry. For the class of current profiles considered, it is found that a new term that accounts for the thermal effects of island asymmetry is required in the modified Rutherford equation. The resultant model is shown to exhibit a robust onset of a rapidly growing tearing mode—consistent with the disruption mechanism observed at the density limit in tokamaks. A fully non-linear 3D cylindrical calculation is performed that simulates the effect of net island heating/cooling by raising/suppressing the temperature in the core of the island. In both the analytic theory and the numerical simulation, the sudden threshold for rapid growth is found to be due to an interaction between three distinct thermal non-linearities which affect the islandresistivity, thereby modifying the growth dynamics.