Nonlinear microtearing modes in MAST and their stochastic layer formation
Nonlinear microtearing modes in MAST and their stochastic layer formation
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MAST 中的非线性微撕裂模式及其随机层形成
DOI：
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发表时间：
2023
影响因子：
2.2
通讯作者：
C. Roach
中科院分区：
文献类型：
--
作者：
M. Giacomin;D. Dickinson;D. Kennedy;B. Patel;C. Roach
首先，在Valovi等人（2011 Nucl. Fusion 51 073045）使用的高碰撞性放电的两个表面上对MAST情况核心中的微撕裂模式进行非线性回旋动力学模拟，以获得有利的能量约束与碰撞性的标度，τE ν −1。在所考虑的表面微撕裂模式占主导地位的离子拉莫尔半径的顺序在副法线长度尺度线性。虽然电子碰撞频率的影响是温和的线性模拟，强烈依赖于这个参数被发现在非线性模拟在r/a=0.5，其中r和a是表面和托卡马克的小半径，分别。微撕裂模式产生的磁岛的动力学进行了分析，表明由岛重叠所造成的随机区域的径向范围起着重要的作用，在确定微撕裂模式驱动的热通量的饱和水平。局部非线性陀螺动力学模拟表明，微撕裂模式驱动的热通量，QeMTM，在很大程度上占主导地位的磁颤振，强烈依赖于磁剪切，S。比较两个表面，r/a=0.5和r/a=0.6，表明QeMTM在r/a=0.5（s =0.34）时可以忽略不计，电子温度梯度（ETG）驱动的热通量QeETG与实验电子热通量Qeexp相当，而QeMTM明显更大，在r/a=0.6（s =1.1）时与QeETG和Qeexp相当。微撕裂模式在更高的S区中引起实验上更显著的输运，并且可以影响（与ETG模式一起）观察到的能量约束时间与碰撞性的比例（Valovietan等人，2011 Nucl. Fusion 51073045）。
First nonlinear gyrokinetic simulations of microtearing modes in the core of a MAST case are performed on two surfaces of the high-collisionality discharge used in Valovič et al (2011 Nucl. Fusion 51 073045) to obtain the favorable energy confinement scaling with collisionality, τE∝ν∗−1 . On the considered surfaces microtearing modes dominate linearly at binormal length scales of the order of the ion Larmor radius. While the effect of electron collision frequency is moderate in linear simulations, a strong dependence on this parameter is found in nonlinear simulations at r/a=0.5 , where r and a are the surface and tokamak minor radius, respectively. The dynamics of magnetic islands generated by microtearing modes is analysed, showing that the radial extent of the stochastic region caused by islands overlapping plays an important role in determining the saturation level of the microtearing mode driven heat flux. Local nonlinear gyrokinetic simulations show that the microtearing mode driven heat flux, QeMTM , is largely dominated by magnetic flutter and depends strongly on the magnetic shear, sˆ . Comparing two surfaces, r/a=0.5 and r/a=0.6 , reveals that QeMTM is negligible at r/a=0.5 ( sˆ=0.34 ), with the electron temperature gradient (ETG) driven heat flux, QeETG , comparable to the experimental electron heat flux, Qeexp , while QeMTM is significantly larger and comparable to QeETG and Qeexp at r/a=0.6 ( sˆ=1.1 ). Microtearing modes cause more experimentally significant transport in higher sˆ regions and may influence (together with ETG modes) the observed scaling of energy confinement time with collisionality (Valovič et al 2011 Nucl. Fusion 51 073045).
影响因子：
2.2
作者：
Colyer, G. J.;Schekochihin, A. A.;Dorland, W.
通讯作者：
Dorland, W.