Simulations Of Edge And Divertor Plasma On EAST Tokamak

The power fluxes on the divertor target is directly related to the success of the operation of the fusion reactors in a steady state mode,which is influenced by the plasma in the edge region.The numerical simulation of edge plasma will help us to have a better understanding of its behavior and to investigate the issue of power fluxes on the divertor.The transport code SOLPS is in widespread use for simulating the edge plasmas of present tokamaks.Due to the uncertainties associated with the cross-field anomalous transport,the values of the particle diffusion coefficient Dr,the electron heat diffusion coefficient χe,and the ion heat diffusion coefficientχi are artificially set in SOLPS modelling,which will bring the uncertainties associated with the SOLPS solutions.The six-field two-fluid model of turbulence code BOUT++can obtain the particle transport coefficients and heat transport coefficients self-consistently.In this work,the new version of fluid plasma/neutral 2D transport code SOLPS,SOLPS-ITER,is used to couple the fluid 3D turbulence code BOUT++.An iterative scheme is used that each system is evolved on its own characteristic time scale.SOLPS-ITER can provide the background profiles of density,ion,and electron temperature to BOUT++.In turn,BOUT++can provide the corresponding radial transport coefficients to SOLPS-ITER.The SOLPS-ITER/BOUT++coupling is used to simulate the edge plasma and divertor plasma on EAST.The MHD equilibrium at the shot time t=5.55s in the shot#56129 on EAST is used for the generation of the meshes in the two codes for the simulation.With the iteration increase,the profiles of density,ion,and electron temperature show fluctuations,and the differences of the changes between two consecutive profiles are getting smaller and smaller.Finally,the self-consistent solutions of turbulence and transport can be obtained.To validated the SOLPS-ITER/BOUT++coupling method,the edge plasma at the time t=3.4s in the shot#36780 with Deuterium discharge on EAST is simulated by the SOLPS-ITER/BOUT++coupling.The profiles of plasma temperature,density,particle flux and heat flux at the divertor targets from the simulation results are compared with the experimental measurement with the Langmuir probes.The convergence of the coupling is validated.The changing rates between the two consecutive profiles of density,electron temperature and ion temperature are less than 1%in the last several iteration steps,and the variations of the transport coefficients also show the tendency to diminish with the iteration step increase,indicating the coupling tends to be in a quasi-steady-state.The computational profiles of electron density,temperature,particle flux f,heat flux P and ion saturation current jsat at the divertor targets from the SOLPS-ITER/BOUT++ coupling simulation are compared to the measured profiles,and it is found that the computational and measured profiles are similar.For the self-consistent simulation of turbulence and transport in tokamak edge plasma by coupling SOLPS and BOUT++,a method of replacing the grids of BOUT++with the grids of SOLPS is proposed to make the simulation region fully consistent with each other.A SOLPS grid file is generated with an MHD equilibrium and used in BOUT++code to simulate the profiles of density,ion and electron temperature with the six-field two-fluid model.The profiles of density,ion and electron temperature in steady state simulated with SOLPS grids are similar with the profiles simulated with BOUT++grids at mid-plane,while the profiles at divertor target show some differences.On the other hand,with the transport coefficients simulated with BOUT++by using the SOLPS grids,the profiles of density,ion and electron temperature from SOLPS are similar with the profiles with the BOUT++grids.Simulation with the common SOLPS grids is meaningful for the SOLPS/BOUT++ coupling.