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Project

Towards validated mean-field descriptions of anomalous transport in the tokamak plasma edge for reactor-relevant regimes

The transport of particles and energy in the plasma egde of tokamaks is dominated by turbulent processes. Since the computational cost of 3D turbulent simulations of the plasma edge is currently too expensive for routine simulations, current plasma edge codes, like SOLPS-ITER, use a mean field description of the plasma. The turbulent transport is typically modelled in these codes with a diffusive relation with ad-hoc diffusion coefficients, which are manually determined by fitting the experimental data with the simulation results. Since these coefficients themselves are dependent on the machine; working regime and can be spatially nonuniform, the predictive capabilities of such simulations are limited. To improve the interpretation of the particle and power exhaust of existing experiments and to design the divertors of future nuclear fusion reactors like ITER and DEMO more reliably improved transport models are necessary. To improve the predictive capabilities, recent research has modelled these anomalous diffusion coefficients more consistently by relating them to turbulent characteristics like the turbulent kinetic energy. Inspired by the Reynolds-Averaged-Navier-Stokes (RANS) techniques, transport equations were derived for the turbulent characteristics and closure relations for the most dominant source and sink terms were formulated by interpreting data coming from turbulent simulations of the plasma edge, generated by the 2D TOKAM2D code. The research so far focused on interchange dominated turbulence in a simplified geometry perpendicular to the magnetic field lines. In this doctoral research these models will be further developed to make their application in realistic plasma edge simulations possible. First these models will be generalized to include the transport of turbulent characteristics along the magnetic field lines. The effect of realistic magnetic topologies (limiters, divertors) on the turbulent transport will be investigated and new physics, due to drift-waves, the sheath and neutrals will be included in the model. Models will be formulated based on data coming from 3D turbulent simulations and Bayesian inference will be used to estimate model parameters and to compare models with each other. The resulting transport models will be finally implemented in SOLPS-ITER, which is used worldwide for the simulation of experiments and the design of future reactors.

Date:29 Oct 2021 →  Today
Keywords:plasma edge turbulence, turbulence modelling, anomalous transport
Disciplines:Fluid mechanics, Nuclear energy, Physics of (fusion) plasmas and electric discharges
Project type:PhD project