Speaker
Description
In the plasma physics, the momentum exchange by charge exchange reactions between plasma ions and boundary neutrals has been underestimated. Lacking of understanding this important mechanism is one of main causes of the complication in the field of plasma surface interaction. When there is magnetic field, perpendicular component of momentum exchange can generate current and the electric field, which is induced by the process of Gyro-Center Shift (GCS). This electric field formation has been observed in the arc discharges, earth’s ionosphere including black aurora, and the edge region of fusion plasmas, especially at the High confinement mode (H-mode) [1]. The perpendicular component of momentum change in the charge exchange reaction is the cause of the intrinsic rotations observed in tokamaks [2]. Overall friction between plasma and neutral generates turbulence, and when the Reynolds number which is the ratio of inertia force to the viscosity force is lower than critical value, the turbulence is suppressed and H-mode transition takes place [3]. The GCS current equation, the turbulence induced diffusion equation, and the Reynold number equation of tokamak boundary will be presented as well as many applications of these equations.
[1] K. C. Lee, Phys. Plasmas 24 112505 (2017)
[2] K. C. Lee, S. G. Lee, Current Appl. Phys. 55 16 (2023)
[3] K. C. Lee, Plasma Phys. Control. Fusion 51, 065023 (2009).