Investigation of power spreading in a tokamak divertor using numerical tools

Divertors are widely used in today's fusion devices in order to reduce plasma core impurities and improve energy confinement. As the divertor targets are exposed to the largest part of the particle and heat loads reaching the wall, these loads must be reduced to prevent material damage. An enhancement of the plasma-wetted area on the targets is one approach. In low density plasmas, the plasma-wetted area is mainly given by the width of the scrap-off-layer (SOL) plasma at the divertor entrance, modified by heat diffusion into the private flux region (PFR) in the divertor. The heat diffusion broadens the heat flux profile at the targets. This can be approximated by a convolution of the upstream profile with a Gaussian of width S. The SOLPS5.0 code package is used to study the influence of divertor geometry and neutral pressure on S. The code is then validated by comparing the numerical results to the experimental findings in the ASDEX Upgrade tokamak.