Simulation Study of Spontaneous Flow Formation in toroidal Plasma System with Open Field Region

磁融合等离子体的约束特性受等离子体流的影响很大。热和粒子的控制取决于等离子体在SOL区的流动。然而，环形等离子体中流动的形成机制迄今尚未得到很好的理解。本研究的目的是研究开场环面等离子体中等离子体的流动。采用颗粒模拟的方法对流动的形成机理和控制方法进行了研究。我们将先前开发的用于直托卡马克系统的二维高级粒子码PARASOL改进为二维环形粒子码PARASOL，使之成为可用于转向托卡马克系统全局模拟的代码。我们在PARASOL中装备了物理模型；用于研究瞬态等离子体流动的高温等离子体碰撞突变源模型和用于直接控制流动的中性束注入源模型。我们一直在改进综合分流流体代码SONIC和集成托卡马克传输代码TOPICS-IB。研究了杂质输运与等离子体流动的相互依赖关系，以及等离子体流动对ELM能量损失的影响。利用一维PARASOL研究了溶胶/导流器等离子体对非对称ELM的瞬态响应，并阐明了非对称热流和等离子体在开放场区的流动结构。利用二维PARASOL，我们发现随着Larmor半径的增大，在闭合场区径向电场由正向负转变。利用环形2D PARASOL进一步研究了香蕉宽度对捕获离子形成径向电场和自发流动的影响。目前的研究成果将有助于对聚变环形等离子体的输运/约束的物理理解，以及改进约束和热/粒子处理的控制方法的发展。

Confinement properties of magnetic fusion plasmas are affected much by the plasma flow. Heat and particle control is dependent on the plasma flow in SOL region. The formation mechanism of the flow in toroidal plasmas, however, has not well understood so far. The present aim is to research the plasma flow in toroidal plasmas with open-field region such as SOL/diveror. The formation mechanism and control method of the flow are investigated with the particle simulation.We improved a two-dimensional advanced particle code PARASOL for the straight tokamak system developed beforehand to a 2D toroidal PARASOL, which becomes the code available for global simulations of divertor tokamaks. We equipped-physics models in PARASOL ; the abrupt source model of hotter temperature plasma at an ELM crash for the study of the transient plasma flow and the neutral beam injection source model for the direct control of the flow. We have been improving a comprehensive divertor fluid code SONIC and an integrated tokamak transport code TOPICS-IB. We studied the mutual dependence between impurity transport and plasma flow, and the effect of SOL plasma flow on the ELM energy loss.By using 1D PARASOL, we investigated the transient response of SOL/divertor plasmas against the asymmetric ELM, and clarified structures of asymmetric heat flow and plasma flow in the open-field region. Using 2D PARASOL, we found the transition of radial electric field from positive to negative in the closed field region with the increase of Larmor radius. We studied further, using toroidal 2D PARASOL, the effect of banana width of trapped ions on the formation of radial electric field and spontaneous flow.Present achievements are expected useful for the physics understanding of transport/confinement of fusion toroidal plasmas, and for the development of control methods of improved confinement and heat/particle handling.