Refining a finite difference-based approach to helium transport analysis*

A He transport model based on spatial finite differences has been developed to quantify increases in helium transport observed in an ITER-like tokamak plasma during RMP-ELM suppression*. Due to coarse spatial sampling in this data, in contrast to conventional methods that compare trial solutions of the continuity PDE to data, a discrete finite-difference approximation to this PDE is used.

 

New work enables this model to be applied with matrix operations, removing human input and greatly improving convergence time. Fits obtain He transport (D, v) profiles, the source’s spatial structure in the plasma edge, the He pump rate, and uncertainties. Pump rates obtained for the Ar-frosted cryopump compare well with earlier work**. This effort aims to simplify transport analysis for application to between shot control-room analysis and potentially also to real-time computation.

 

*E.T. Hinson et al 2020 Nucl. Fusion 60 054004

**M. M. Menon, et al, J. Vac. Sci. and Tech. A 13, 551 (1995)