Investigation of plasma turbulence in tokamak divertor and its implications for plasma-material interactions

Turbulent fluctuations in the tokamak divertor region are important for the plasma-facing components since plasma-material interaction processes, such as sputtering, are strongly nonlinear. In this study, a fluid edge plasma turbulence model SOLT3D is used for investigation of divertor plasma turbulence and plasma interaction with the material surfaces. The model, implemented in the BOUT++ framework [1], includes equations for collisional fluid plasma and neutral gas, with sheath boundary conditions on the divertor target plates. The computational domain represents the edge plasma region of a tokamak in a “rectified” geometry. The model supports basic fluid plasma instabilities relevant to the SOL and divertor: the drift- resistive-ballooning mode instability, driven by the magnetic curvature and the radial gradient of plasma pressure, and the conducting-wall mode instability, driven by the end-plate sheath boundary conditions and the radial gradient of plasma temperature. Comparison with linear dispersion relations and some existing nonlinear results demonstrates excellent consistency. Results for simulated plasma turbulence in the divertor region are presented, and implications of turbulent fluctuations for plasma-material interactions are discussed.

[1] Dudson et al., Comput. Phys. Commun. 180, 1467–1480 (2009).