Modelling Of The Effects Of Classical Drifts On Edge Plasma And Impurity Transport In EAST

The control of particle and heat flux on divertor is one of the most critical issues to be solved for the long-pulse and high-power operation of the future fusion devices.Divertor asymmetry can be driven by the classical drifts,the different distributions of the particle and heat sources in the inboard and outboard sides,e.g.enhanced ballooning-like transport near the outboard mid-plane.However,the change of the divertor asymmetry is usually associated with the classical drifts,including the E x B drift and the grad-B drift.To predict and interpret the effects of the classical drifts on the divertor asymmetry,modelling on the main characteristics of the divertor heat and particle fluxes in different configurations with variety drifts in EAST has been performed by using the latest version of boundary simulation code-SOLPS-ITER.Simulation indicates that the E×B play a significant role in the edge plasma thus generating the massive in-out asymmetry in the LSN/USN while the Pfirsch-Schluter(PS)flow driven by E×▽B drifts does influence in the parallel flow evidently.In the LSN normal Bt case,more particle flow flows onto inner divertor which imply the ignificant increase of ne/Jsat and decrease of the Te/qt in the board,generating noticeable in-out asymmetry.And the situation is reversed for the reversal Bt case.As to the USN,when in the reversal Bt case,the results are similar with the LSN normal Bt case,the particle flux on inner diverotor increased while on outer one decreased.Andthe USN normal Bt case is the same as the LSN reversed Bt case.It is also found that the in-out asymmetry is more serious in the LSN situation.With the extensive use of tungsten materials in tokamak,the understanding on the characteristics of thetungsten impurities generation and its transport plays an important role of the long-pulse and high-power operation.DIVIMP modeling of W impurity transport for an EAST upper single null discharge is conducted.The results indicate that due to the friction plays a decisive role in impurity transport,under the condition of reversal field,the parallel flow velocity is bigger and generatinglarger friction,so compared with thenormal field,there are lower W impurity core leakage and lower W content in core plasma.