Impact of drifts in edge plasma of small size divertor tokamak

The effect of poloidal E × B and diamagnetic drifts in edge plasma of Small Size Divertor (SSD) Tokamak is studied with two-dimensional B2SO- LPS-0.5.2D fluid transport code. The simulation results show the following: 1) For normal toroidal magnetic field, the increasing of core plasma density leads to large divertor asymmetries due to poloidal E × B and diamagnetic drifts. 2) Switching on the E × B and diamagnetic drifts leads to large change in poloidal distribution of radial electric field and induced counter-clockwise circulation (flow) around the x-point. 3) Switching on the E × B and diamagnetic drifts leads to the structure of poloidal distribution of radial electric field is nonmonotonic which responsible for negative spikes. 4) Switching on the E × B and diamagnetic drifts in vicinity of separatrix leads to the structure of poloidal distribution of radial electric field that has viscous layer. 5) Switching on the E × B and diamagnetic drifts results in torque generation. This torque spins up the toroidal rotation. 6) The E × B drift velocity depends on the plasma temperature heating and doesn't depend on plasma density.

Simulation of small size divertor tokamak plasma edge under effect of toroidal magnetic field reversal

Asymmetries between the divertor legs of small size divertor (SSD) tokamak plasma edge are noticed to reverse when the direction of toroidal magnetic field is reversed. In the present paper the small size divertor tokamak plasma edge under effect of toroidal magnetic field reversal is simulated by B2SOLPS0.5.2D fluid transport code. The simulation demonstrate the following results: 1) Parallel (toroidal) flow flux and Mach number up to 0.6 at higher plasma density reverse with reverse toroidal magnetic direction in the edge plasma of small size divertor tokamak. 2) The radial electric field is toroidal magnetic direction independence in edge plasma of small size divertor tokamak. 3) For normal and reverse toroidal magnetic field, the strong ITB is located between the positions of the maximum and minimum values of the radial electric field shear. 4) Simulation result shows that, the structure of radial electric field at high field side (HFS) and low field side (LFS) is different. This difference result from the change in the parallel flux flows in the scrape off layer (SOL) to plasma core through separatrix. 5) At a region of strong radial electric field shear, a large reduction of poloidal rotation was observed. 6) The poloidal rotation is toroidal magnetic field direction dependence.