Impact de la collisionalité sur les propriétés du transport et de la turbulence dans le plasma de bord d'un tokamak

La collisionnalité est l'un des paramètres clés pour déterminer les turbulences transport dans le bord du plasma, régulant des phénomènes tels que la "formation d'épaule", séparation des longueurs d'échelle dans la couche de raclage, amortissement des turbulences et écoulement zonal dynamique. Comprendre son rôle est donc primordial pour les futurs réacteurs comme ITER. Obtenir des prédictions fiables et une meilleure caractérisation du flux plasma propriétés lorsque la collision variable reste, cependant, un défi critique pour les simulations. Cet article se concentre sur l'impact des variations de collisions dans un modèle fluide tridimensionnel non isotherme du bord du plasma. Un côté haut champ limité configuration comprenant des lignes de champ magnétique ouvertes et fermées avec des paramètres typiques d'un tokamak de taille moyenne est considéré. Le modèle actuel peut tenir compte des variations de collisions et de son impact à la fois sur la résistivité parallèle ηk et les conductivités thermiques parallèles ionique et électronique χke; i. Un ensemble de simulations est effectué à différentes collisions avec le code TOKAM3X. Les simulations sont analysées à la fois en termes de turbulence et de propriétés de transport et dans le paradigme filaments / blob. A la fin, un aperçu rapide est donné sur la vérification du code avec la méthode (i) PoPeCollisionality is one of the key parameters in determining turbulent transport in the plasma edge, regulating phenomena such as "shoulder formation", separation of scale lengths in the scrape-off layer, turbulence damping, and zonal flow dynamics. Understanding its role is therefore of primary importance for future reactors like ITER. Obtaining reliable predictions and a better characterization of plasma flowproperties when varying collisionality remains, however, a critical challenge for the simulations. This manuscript focuses on the impact of varying collisionality in a nonisothermal three-dimensional fluid model of the plasma edge. A high field side limited configuration encompassing open and closed magnetic field lines with parameters typical of a medium-sized tokamak is considered. The present model can consistently account for the variations of collisionality and its impact on both the parallel resistivity ηk and the ion and electron parallel thermal conductivities χke. A set of simulations is performed at various collisionality with the TOKAM3X code. The simulations are analyzed both in terms of turbulence and transport properties and in the paradigm of filaments / blob. At the end, a quick overview is given on the verification of the code with the (i) PoPe metho

Impact of collisionality on turbulence in the edge of tokamak plasma using 3D global simulations

International audienceCollisionality is one of the key parameters in determining turbulent transport in the plasma edge, regulating phenomena such as "shoulder formation", separation of scale lengths in the scrape-off layer, turbulence damping and zonal flow dynamics. Understanding its role is therefore of primary importance for future reactors like ITER. Obtaining reliable predictions and a better characterization of plasma flow properties when varying collisionality remains, however, a critical challenge for the simulations. This paper focuses on the impact of varying collisionality in a nonisothermal three-dimensional fluid model of the plasma edge. A high field side limited configuration encompassing open and closed magnetic field lines with parameters typical of a medium-sized tokamak is considered. The present model can consistently account for the variations of collisionality and its impact on both the parallel resistivity η and the ion and electron parallel thermal conductivities χ e,i. Details on mean flow and turbulence properties are given. Changing collisionality leads to significant changes in the flow properties both on the mean and fluctuating quantities. In particular, lowering collisionality decreases the size of coherent structures, the fluctuation levels of turbulence, and steepens the density and temperature equilibrium profiles around the separatrix leading to a global reduction of the turbulent transport. The scrape-off layer (SOL) width is observed to increase with collisionality, eventually resulting in the disappearance of the scale lengths separation between near and far SOL, consistently with previous experimental observations. At low collisionality, where the presence of narrow feature is well-established, a contribution of heat conduction increases up to compete with heat convection

Self-generated reversed radial electric field in 3D global flux-driven fluid edge plasma turbulence simulations

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IMPACT OF COLLISIONALITY ON TURBULENCE IN THE EDGE PLASMA AND SCRAPE-OFF LAYER (SOL)

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