Interpretive Modeling of DIII–D Edge Measurements Using the OEDGE Code

1. INTRODUCTION Interpretive code simulations play an essential role in divertor/edge physics, firstly, because the edge is intrinsically complicated: at least 3 states of matter are involved; the shape of the region is problematical: long, narrow, twisted, inaccessible; edge modeling must be at least 2D; etc. Meaningful interpretive exercises therefore require that a data set of edge measurements, which is as large as possible, be confronted simultaneously using a code. Secondly, the significance of many edge data is not directly evident and they can only contribute to a picture of the edge using an interpretive code. Thirdly, edge data sets are invariably incomplete but extrapolation is not usually adequate because variations along B are often non-linear. All this tends to place interpretive codes at the center of edge studies with the various lines of diagnostic information feeding into the hub as well as our ideas about what the controlling physics effects might be. To help identify the controlling processes in the edge, an iteratively coupled code, OEDGE, is being developed and benchmarked against well-diagnosed, simple plasmas. OEDGE ('Onion-Skin Modeling + EIRENE + DIVIMP for edge analysis'). EIRENE is a neutral hydrogen Monte Carlo code developed by D Reiter, KFA Jülich [1]. DIVIMP is an impurity neutral and ion Monte Carlo code [2]. The Monte Carlo codes require a " plasma background " into which to launch particles. The Onion-Skin Modeling, OSM, code [3,4] can provide such a background by solving the 1D, along-B, plasma (fluid) conservation equations using across-B boundary conditions from experiment, e.g. I sat + and T e across divertor targets