Impact of drifts in edge plasma of small size divertor tokamak

Amr H Bekheit

doi:10.4236/ns.2012.42019

Abstract

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.

Highlights

The divertor asymmetry has been observed experimentally in several tokamaks with a single null divertor configuration [1,2,3,4,5]
This paper demonstrated with core density increasing, the divertor asymmetries due to poloidal E × B and diamagnetic drifts is large for normal toroidal magnetic field and switching E × B and diamagnetic drifts leads to large change in poloidal distribution of radial electric field and induced counter-clockwise circulation around the x-point
The simulation provides the following result: 1) With core density increasing, the divertor asymmetries due to poloidal E × B and diamagnetic drifts is large for normal toroidal magnetic field

Summary

Introduction

The divertor asymmetry has been observed experimentally in several tokamaks with a single null divertor configuration [1,2,3,4,5]. The asymmetry of the plasma density and temperature in front of the inner and outer divertor plates changes with the sign of the toroidal magnetic field, BT [1,6], and the power threshold for the L-H confinement transition often depends on the direction of BT [1,6].

Results

Conclusion