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International audience; A two-equation model to self-consistently determine cross-field fluxes in the edge and scrape-off layer region of diverted plasma is used to complete 2D mean-field edge transport description of plasma wall interaction. Inspired by the Reynolds Average Navier-Stokes simulations for neutral fluids, this model is based on the local evolution of the turbulent kinetic energy κ and its dissipation rate ε. These two equations are algebraically derived for RANS modeling and are very slightly modified and adapted to describe self-consistent plasma turbulent transport. The general features of the model are discussed and bridged to the well-known predatorprey and quasilinear models commonly used to investigate plasma transport. Specific closures are proposed based on the interchange turbulence. Results of the 1D model are confronted to experimental evidence by analyzing the computed SOL width and comparing the results to the existing scaling law for L-mode plasmas. Introducing a dependence on the shear of large scale flows, typically the zonal flows, 1D simulations can exhibit an H-mode like transition when increasing the input power, generating an increased stored energy thanks to an interface barrier located at the separatrix. Further 2D plasma-wall interaction simulations for WEST are analyzed that show a good match with the experimental profiles, as well as a ballooned transport driving turbulent transport in the divertor SOL and nearly no transport in the private flux region. The SOL width of WEST is also recovered. These results show the remarkable capability of the κ-ε model to capture key aspects of the physics of turbulent transport throughout the plasma knowing that a unique scalar free parameter is available to tune cross field transport in the whole 2D cross section of the plasma.

International audience; In this paper, a κ−ϵ transport model is presented as a turbulence reduction tool for a typical ohmic L‐mode discharge plasma in a divertor‐configurated tokamak. Taking a Tokamak à configuration variable (TCV) study case, a feedback loop procedure is performed using the SolEdge2D code to acquire plasma diffusivity at the outer mid‐plane. The κ−ϵ model is calibrated through its free parameters with the aim of recovering the diffusivity calculated in the feedback procedure. Finally, it is shown that the model can self‐consistently calculate diffusivity in the whole domain, recovering the poloidal asymmetries due to interchange instabilities.

A reduced model for radial anomalous transport of plasma in tokamaks, inspired by the Reynolds-Averaged Navier–Stokes (RANS) approach, is presented assuming diffusion as governing mechanism. In order to self-consistently calculate transport coefficients, an empirical equation is built for the turbulent kinetic energy and the system is closed via the scaling law of global confinement. In such way the SOL width appears to recover experimental dependencies with respect to machine parameters and interestingly, when the model is implemented in a 2D transport code for a realistic study-case, mean fields retrieve some features already observed in 1st-principle turbulent codes. Keywords: Anomalous transport, Reduced model, κ−ε

A reduced model for the anomalous transport of magnetically confined plasma in the edge and SOL, inspired by the Reynolds-Averaged Navier-Stokes (RANS) approach, is presented assuming diffusion as governing mechanism. An empirical equation is built for the turbulent kinetic energy and the system is closed via the scaling of global confinement, the experimental dependencies to machine parameters being recovered for the SOL width. The model is implemented in the transport code SolEdge2D and tested with respect to three magnetic configurations of TCV. Profiles of density, temperature and perpendicular heat flux are then compared to experimental data. Particular attention is devoted to the effect of the magnetic configuration on the SOL width and particle transport coefficient to different configurations.

International audience; The staircase transport regime reported in kinetic simulations of plasma turbulent transport in magnetic confinement is recovered with a simple 2D fluid model allowing for reduced damping of the zonal flows. Some of the complex dynamics of the kinetic zonation regime are recovered but the pattern of the corrugation appears to be sinusoidal with a characteristic scale comparable to that of turbulence modes with largest spectral energy, in contrast to regimes observed in global and flux-driven kinetic simulations. Enhanced zonal flows govern both an overall reduction of the SOL width and a gradual steepening of the gradients with distance to the separatrix.

International audience; Operation of high performance fusion plasmas relies on self-organised properties to reach appropriate working points that are compatible with both high confinement performance to achieve a burning plasma, and controlled ageing of the confinement device. The latter conditions requires a trade-off between simplicity of the operation point and reaching conditions that can be sustained in steady state. The issue of heat flux control at the plasma edge and onto the plasma facing components is an example of this synergy. We address in this framework the problem of radiative divertor operation. The simplified 1D problem is recast in Hamiltonian formalism, the effective energy being invariant. This property is most efficient to address bifurcations and critical points leading to no-solution regions of the parameter space. Analytical investigation of these solutions indicates that taking into account the radiative front location and constraints on the upstream temperature reduces the operation space. Furthermore, one finds that radiative divertor operation tends to lead to operation at reduced plasma pressure, unless stable conditions and hot upstream plasma temperature can be sustained at vanishing divertor temperature.