Modeling of Transport-Limited, Near-Edge Tokamak Profiles Using Control Volumes

Accurately predicting temperature and density profiles in the near-edge region between the core and scrape-off layer (roughly the outer 10%-20% of closed flux surfaces) is essential for self-consistent modeling of tokamak performance. We present initial results from a new approach to predicting these profiles, building upon lessons learned from advances in core transport and stability modeling. Model forms such as “modified” tanh functions or piecewise-linear scale lengths are used to describe density and temperature profiles with only a small number of free parameters. These parameters are determined by a combination of prescribed boundary conditions and discretization of the flux-surface averaged transport equations via control volumes. For this initial work, only simple analytic expressions of neoclassical and stiff turbulent transport are used, but extensions to more complex models is straightforward. The net result is that self-consistent solutions can be determined by solving a relatively small set of equations with standard root-finding and minimization techniques. Illustrative examples of the predictions and their key parametric dependencies will be shown, and future development directions discussed.



This work was supported by the US DOE under award DE-SC0018287.