Speaker
Description
Mean-field fluid edge codes are widely used for planning operations of magnetic fusion devices. Turbulence, a key factor in edge transport, is represented in these codes via diffusion coefficients tuned to match the Scrape-Off Layer (SOL) power fall-off length to existing experimental scaling laws, which are derived from attached plasmas. However, experimental results indicate that high-density regimes significantly impact SOL transport [1], limiting the applicability of the existing scaling laws when modelling high-density regimes. High edge density will be necessary for the operation of high-performance devices, in order to achieve enough plasma-neutral interactions to protect the plasma-facing components. To further inform the choice of diffusion coefficients in mean-field simulations of high-density regimes, turbulence and neutrals should be modelled self-consistently. In this work, we demonstrate edge fluid simulations with the SOLEDGE3X 3D turbulence code including a self-consistent 3-moment fluid neutrals model as derived by Horsten et al. [2], applied to TCV geometry with a long outer divertor leg [3]. This model is a significant improvement from the previous 1-moment fluid neutrals model implemented by Quadri et al. [3]. In mean-field simulations, the model is shown to reduce error between the plasma sources computed by fluid neutrals and EIRENE kinetic neutrals, and results in a less deeply detached plasma which is in better agreement with experimental results. First results of 3D turbulent simulations with the 3-moment fluid neutrals model concur with the results of the 1-moment fluid neutrals model, with detachment being associated with an increase in the SOL transverse transport and leading to a broadening of the SOL power fall-off length. Turbulent structures in the outer divertor leg are found to be qualitatively similar to experiment, with the size and velocity of the fluctuations depending on the divertor density regime.
[1] T. Eich et al. 2020 Nucl. Fusion 60 056016
[2] N. Horsten et al. 2017 Nucl. Fusion 57 116043
[3] V. Quadri et al. 2024 Nucl. Mater. Energy 41 101756