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

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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.