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Hoshino, Kazuo; Takizuka, Tomonori; Nakano, Tomohide
Contributions to Plasma Physics, 50(3-5), p.386 - 391, 2010/05
Times Cited Count：6 Percentile：23.46(Physics, Fluids & Plasmas)The accumulation process of high-Z impurity in toroidal rotating tokamak plasma is investigated. A new inward pinch of high-Z impurity due to the ionization/recombination processes is derived using an analytical model. This inward pinch is driven by the large deviation of a drift orbit from a magnetic surface and the resultant variation of the charge state along the drift orbit. The pinch velocity increases with increasing toroidal rotation speed in both the co- direction and the ctr-direction. The inward pinch expected by the analytical model is really observed in the numerical simulation using the IMPGYRO code.
Takizuka, Tomonori; Hoshino, Kazuo; Shimizu, Katsuhiro; Yagi, Masatoshi*
Contributions to Plasma Physics, 50(3-5), p.267 - 272, 2010/05
Times Cited Count：6 Percentile：23.46(Physics, Fluids & Plasmas)The plasma flow in the scrape-off layer (SOL) plays an important role for the control of heat and particle including impurity in magnetic fusion reactors. SOL flow patterns have recently been studied by the particle simulations, and the effects of finite-orbit-size of ions are found to be essential for the flow-pattern formation. Based on these simulation results, a new model of the edge plasma flow is developed by introducing the "ion-orbit-induced flow" to the fluid equations. A tokamak plasma is divided into three regions; core region, transition layer and SOL region. The "ion-orbit-induced flow" is modeled by separating untrapped part and trapped part, and by taking account the collision effect and poloidal distribution. The "ion-orbit-induced flow" becomes large at the edge region.
Froese, A.*; Takizuka, Tomonori; Yagi, Masatoshi
Contributions to Plasma Physics, 50(3-5), p.273 - 278, 2010/05
Times Cited Count：8 Percentile：30.72(Physics, Fluids & Plasmas)Electron heat transport parallel to magnetic field in the SOL is studied via fully kinetic simulations using the one-dimensional particle code PARASOL. The heat flux in fluid model is usually approximated with the Spitzer-Harm value in the collisional case, and the free-streaming value adjusted by a limiting factor in the collisionless case. While typically taken to be a constant 0.1, we survey the dependence of the limiting factor with respect to plasma parameters (collisionality, type of source and sink etc). It is found that the limiting factor is strongly affected by the collisionality, covering magnitude from 0.01 to 10. A high-energy tail plays an important role for this large variation. Langevin heating source maintains a Maxwellian electron energy distribution, and the limiting factor remains between 0.05 and 0.3. It is also found that the radiation loss is essential to increase the limiting factor.
