Simulation Study of Detached Plasmas by Using Advanced Particle Model and Fluid Model
T. Takizuka1), K. Shimizu1), N. Hayashi1), M. Hosokawa2)
1) Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Naka, Japan
2) Research Organization for Information Science & Technology, Tokai, Japan
Abstract.
Fluid simulations and particle simulations are performed to understand the physics of detached plasmas in the tokamak divertor. Two dimensional fluid simulations show that detached divertor plasmas are formed for the high density operation in the W-shaped divertor configuration of JT-60U tokamak. Charge- exchange and recombination processes play important roles to cause the detachment. The asymmetry of inner-and-outer divertor plasmas is studied based on a fluid model, and the bifurcated nature of the asymmetry caused by the SOL current is found. Advanced particle simulations demonstrate that the ExB drift by the radial electric field in a SOL plasma causes the asymmetry of flow pattern and density profile. A detached plasma is formed in the divertor region from which the drift flows out, when the ratio of the ExB drift speed to the sound speed exceeds a threshold. Effects of the radial gradient including diamagnetic drift flow on SOL and divertor plasmas are also studied with the two-dimensional particle simulation.