In many regimes of interest, the transport of neutral gas in a divertor is efficiently computed by the Monte Carlo method. This method deals with the kinetic limit where the mean free path is of the order of or greater than the typical scale lengths in the problem. In addition, it is straightforward to deal with complex (three-dimensional) geometries and to accommodate numerous atomic, molecular, and surface reactions within the scope of a Monte Carlo method.
Degas 2 is a Monte Carlo code, developed at Princeton, for the study of neutral gas transport in divertors. In the paper we discuss the scoring implemented in Degas 2. Scoring is the method by which estimates of physical quantities are made from an analysis of the properties of the sampled neutral trajectories.