Gyrokinetic simulations including the centrifugal force in a rotating tokamak plasma
Gyrokinetic simulations including the centrifugal force in a rotating tokamak plasma
复制标题
DOI：
10.1063/1.3491110
复制
发表时间：
2010-10
影响因子：
2.2
通讯作者：
F. Casson;A. Peeters;C. Angioni;Y. Camenen;W. Hornsby;A. Snodin;G. Szepesi
中科院分区：
文献类型：
--
作者：
F. Casson;A. Peeters;C. Angioni;Y. Camenen;W. Hornsby;A. Snodin;G. Szepesi
托卡马克实验使用旋转等离子体，其环形速度可以由外部驱动，但也可以自发产生。在与等离子体共同旋转的框架中，通过离心漂移和增强的镜像力感受到离心力的影响[Peeters et al., Phys.等离子体 16, 042310 (2009)]。这些惯性项在强旋转的情况下变得很重要（这在球形装置中很常见），并且即使在小环形速度下对于重杂质离子也很重要。在这项工作中，首次进行了回旋运动模拟，包括强烈旋转等离子体中的离心力。增强的镜像力重新分布通量表面上的密度并修改捕获条件，从而使捕获的电子模式不稳定。在中间尺度上，这可能导致俘获电子模式超过离子温度梯度（ITG）模式，成为主要的不稳定性，这在边缘条件下可能导致电子热通量增强。离心漂移的作用是抑制地声模式的残余纬向流，同时其频率增加。对于非线性 ITG 主导的湍流，如果增加的旋转没有伴随旋转剪切稳定，则增加的俘获电子驱动和减少的层流会导致离子热扩散率增加。慢速俘获电子比例的增加增强了对流粒子箍缩，导致稳态密度梯度随着强旋转而增加。线性 ITG 模式结果显示，由于其强大的离心捕获作用，重痕量杂质的夹带量有所增加。
Tokamak experiments operate with a rotating plasma, with toroidal velocity which can be driven externally but can also arise spontaneously. In the frame that corotates with the plasma, the effects of the centrifugal force are felt through a centrifugal drift and an enhanced mirror force [Peeters et al., Phys. Plasmas 16, 042310 (2009)]. These inertial terms become important in the case of strong rotation, as is common in spherical devices, and are also important for heavy impurity ions even at small toroidal velocities. In this work, the first gyrokinetic simulations including the centrifugal force in a strongly rotating plasma are presented. The enhanced mirror force redistributes density over a flux surface and modifies the trapping condition, destabilizing trapped electron modes. At intermediate scales this can result in promotion of the trapped electron mode over the ion temperature gradient (ITG) mode as the dominant instability, which under marginal conditions could result in an enhanced electron heat flux. The centrifugal drift acts to damp the residual zonal flow of the geoacoustic mode, while its frequency is increased. For nonlinear ITG dominated turbulence, increased trapped electron drive and reduced zonal flow lead to an increase in ion heat diffusivity if the increased rotation is not accompanied by rotational shear stabilization. An increased fraction of slow trapped electrons enhances the convective particle pinch, leading to an increase in the steady state density gradient with strong rotation. Linear ITG mode results show an increased pinch of heavy trace impurities due to their strong centrifugal trapping.