Impact of safety factor and magnetic shear profiles on edge turbulence in circular limited geometry

International audienceThe impact of magnetic configuration on edge turbulence properties in circular limiter geometry is investigated using TOKAM3X, a three-dimensional (3D), first-principle, fluid code for edge plasma. The theoretical spatial tilting of magnetic shear on turbulence fluctuations is recovered. Magnetic shear is found to generate or enhance poloidal high/low field sides (HFS/LFS) and up/down asymmetries. A simulation mimicking the impact of an X-point on circular limiter geometry leads to the formation of two transport barriers that are stable in time, thus leading to the improvement of core particle confinement and to reduction of radial turbulent transport. The magnetic shear, which also strongly enhances the E × B shear, is responsible for the barrier formation

PoPe (Projection on Proper elements) for code control: verification, numerical convergence and reduced models. Application to plasma turbulence simulations

The Projection on Proper elements (PoPe) is a novel method of code control dedicated to 1) checking the correct implementation of models, 2) determining the convergence of numerical methods and 3) characterizing the residual errors of any given solution at very low cost. The basic idea is to establish a bijection between a simulation and a set of equations that generate it. Recovering equations is direct and relies on a statistical measure of the weight of the various operators. This method can be used in any dimensions and any regime, including chaotic ones. This method also provides a procedure to design reduced models and quantify the ratio costs to benefits. PoPe is applied to a kinetic and a fluid code of plasma turbulence

Implementation of drift velocities and currents in SOLEDGE2D-EIRENE

International audienceIn order to improve cross-field transport description, drifts and currents have been implemented in SOLEDGE2D-EIRENE. The derivation of an equation for the electric potential is recalled. The resolution of current equation is tested in a simple slab case. WEST divertor simulations in forward-B and reverse-B fields are also discussed. A significant increase of ExB shear is observed in the forward-B configuration that could explain a favorable L-H transition in this case

Numerical modeling with SOLEDG2D transport code for divertor design and in support to the WEST project

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L'Interface Plasma-Paroi

International audienceDans l'histoire de la recherche sur la fusion par confinement magnétique, l'interface entre le plasma et la paroi n'a pas toujours été sur le devant de la scène. Près de 70 ans après les premiers tokamaks, contrôler le plasma de bord et son interaction avec la paroi est devenu un enjeu majeur et une thématique de premier plan dans la recherche en fusion

Investigation of the dependency of midplane separatrix density as a function of engineering parameters for H-mode pulses in JET with the ITER Like Wall

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Particle recirculation simulations including main chamber walls with the SOLEDGE2D-EIRENE transport code

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Global fluid simulations of edge plasma turbulence in tokamaks: a review

International audienceWith ITER, the largest tokamak ever built, and the growing number of fusion energy startups in the world, the need for numerical simulations has never been more crucial to progress towards the successful operation of fusion reactors. From fundamental plasma physics to engineering, a hierarchy of models exists from high-fidelity (gyro-)kinetic models in (5D) 6D to 0D fluid transport models. In this paper, we review the state-of-the-art of 3D turbulence fluid simulations in edge tokamak configurations. The widely used drift-reduced Braginskii equations are introduced together with the dedicated boundary conditions modelling plasma wall interactions. If until recently most of the models were focused on electrostatic turbulence driven by interchange-like instabilities, in recent years models have incorporated electromagnetic effects allowing fluctuations of the magnetic field. Specific features of the edge plasma configurations, which make these equations specially challenging to resolve and stressful for the numerical methods, are detailed. In particular, the strong anisotropy of the flow as well as the complex geometric characteristics lead to the development of dedicated discretization schemes and meshing, which are implemented in state-of-the-art codes reviewed here. It appears that the latter can be differentiated by their mesh construction as well by the manner in which they handle parallel gradients (aligned or not along the magnetic field). The review shows that no consensus on the optimal combination between meshing and discretization schemes, if it exists, has been found. Finally, examples of recent achievements show that 3D turbulence simulations of medium-sized tokamaks are currently achievable, but that ITERsize tokamaks and thermonuclear plasmas still require significant progress