Development of the neutral model in the nonlinear MHD code JOREK: Application to E × B drifts in ITER PFPO-1 plasmas

Abstract

The prediction of power fluxes and plasma-wall interactions impacted by MHD processes during ITER operation [disruption, Edge Localized Modes (ELMs), 3D magnetic fields applied for ELM control, etc.] requires models that include an accurate description of the MHD processes themselves, as well as of the edge plasma and plasma-wall interaction processes. In this paper, we report progress on improving the edge plasma physics models in the nonlinear extended MHD code JOREK, which has capabilities to simulate the MHD response of the plasma to the applied external 3D fields, disruptions and ELMs. The extended MHD model includes E × B drifts, diamagnetic drifts, and neoclassical flows. These drifts can have large influences, on e.g., divertor asymmetries. Realistic divertor conditions are important for impurity sputtering, transport, and their effect on the plasma. In this work, we implemented kinetic and fluid neutral physics modules, investigated the influence of poloidal flows under divertor conditions in the ITER PFPO-1 (1.8T/5MA) H-mode plasma scenario, and compared the divertor plasma conditions and heat flux to the wall for both the fluid and kinetic neutral model (in JOREK) to the well-established 2D boundary plasma simulation code suite SOLPS-ITER. As an application of the newly developed model, we investigated time-dependent divertor solutions and the transition from attached to partially detached plasmas. We present the formation of a high-field-side high-density-region and how it is driven by poloidal E × B drifts.

Influence of the magnetic configuration on the high-field side scrape-off layer at ASDEX Upgrade and the role of the secondary separatrix

“…This observed behavior can potentially be attributed to the effect of E×B drifts redistributing particle flows in the divertor [10,11], as this effect has been consistently observed across all shots studied. However, it is important to note that other mechanisms such as alternative neutral ionization pathways could also contribute to the observed spreading, and a comprehensive evaluation of these mechanisms was not performed in this study.…”

“…The high-density region in the HFS divertor is sustained by the parallel heat conducted from the LFS midplane and by the drift-driven cross-field particle fluxes from the LFS divertor resulting from E × B drifts [9][10][11]. The high-density region depends on the available heat flux reaching the region of strong ionization at the HFS divertor and forms with sufficient heating power [8,12].…”

Modelling of vertical displacement events in tokamaks: status and challenges ahead

“…These include the discontinuities of parallel velocity and electric potential across the tangent (limiter) point, the necessity for increased resolution to resolve large gradients at the plasma boundary, and the requirement of low viscosity to prevent unphysical current density gradients along magnetic field lines [59]. Recent modelling of edge physics in JOREK including a kinetic neutral model, sheath boundary conditions and sputtering for static plasmas [62] will be applied and further developed for disruption applications.…”

Probing non-linear MHD stability of the EDA H-mode in ASDEX Upgrade

“…At this stage it is worth mentioning that the simplified scrape-off layer model used in the single-temperature JOREK simulation results in a radial electric field that is unrealistic in the SOL. Future work may then involve a more advanced SOL model [42] and a separation between ion and electron temperatures to understand the influence onto the mode dynamics, but this goes beyond the scope of the present work.…”