No abstract

A complete system of transport equations with all the important perpendicular currents is derived for the simulation of tokamak edge plasma. These transport equations are implemented in the B2.5 code and solved for the parameters of the ASDEX Upgrade tokamak. The relative roles of different mechanisms of transverse conductivity in the formation of the potential profile are studied. It is demonstrated that a reasonable potential distribution in the tokamak edge plasma can be obtained without an ad hoc assumption of the existence of the anomalous perpendicular conductivity. The role of E × B drifts in the redistribution of edge plasma and closing of the currents in the plasma is analysed.

We present in this paper the code package SOLPS-ITER, initially introduced by S. Wiesen et al. [J. Nucl. Mater. 463, 480 (2015)], dedicated to simulations of plasmas in the edge region of fusion devices. This package brings together previously existing SOLPS implementations and aims to become the new standard SOLPS version. We summarize the benchmarking work done to ensure backward compatibility with previous work, with a strong requirement on maintaining the viability and usability of the already extensive database of SOLPS runs used for the ITER divertor design and edge plasma physics studies worldwide over the years. The SOLPS-ITER package includes not only the plasma (B2.5) and neutral (Eirene) transport solvers, but also a large set of software tools for input file build-up, conversion of old runs, inline run analysis, and post-processing, all within a standardized portable run environment and version control system. Ongoing and planned upgrades to the code, such as extending the computational domain to the full vacuum vessel wall and a new graphical user interface, are also discussed.

A new B2SOLPS5.2 transport code has been developed and implemented for the simulation of H-mode shots. A new equation system is proposed, which is equivalent to the system which was used in B2SOLPS5.0 previously. The main idea is to replace the major part of the large radial ∇B driven convective fluxes by poloidal fluxes with the same divergence both in the particle balance and in the energy balance equations. This is of special importance for the H-mode where the diffusion coefficient is strongly reduced inside the barrier and large radial convective flows are strongly undesirable from the numerical point of view. The H-mode shots of ASDEX-Upgrade and MAST have been simulated with the new version with reasonable time steps and convergence. It is demonstrated that the radial electric field inside the edge transport barrier and in the pedestal region is close to the neoclassical electric field as in previous simulations of Ohmic shots. The toroidal rotation is co-current directed as in L-mode but is significantly larger in absolute value. It is shown that the shear of the poloidal drift at the inner side of the barrier is close to the value of the shear before the transition, while inside the barrier the value of the shear is significantly bigger. This fact determines self-consistently the width of the edge transport barrier. It is demonstrated that to match the experimental density and temperature radial profiles the drop in the diffusion coefficient within the barrier needs to be significantly larger than the drop in the electron heat conductivity coefficient. For the H-mode the pedestal region usually corresponds to the collisionless regime, so several corrections were introduced into the transport coefficients to extend the applicability of the code to the plateau and banana regimes in the inner regions of the simulation domain.