Benchmark of the 3-dimensional plasma transport codes E3D and BoRiS

The next generation of experiments - both for tokamaks and stellarators - requires the development of appropriate theoretical models. One important aspect here is the plasma edge physics description. Fluid transport codes extending beyond the standard 2-D code packages like B2-Eirene or UEDGE are under development. In the case of tokamaks, an interesting alternative line is the concept of an ergodic edge (necessary e.g. for ergodic divertors in TORE SUPRA or TEXTOR-94) creating a 3-D edge structure. To study these effects, a 3-D code E3D based upon a Multiple Coordinate Systems Approach is being developed. Presently, we are extending the program towards stellarator applications. A few new options are made available: single-island geometry and now formulation of boundary conditions. For the new stellarator W7-X, a 3-D finite volume code BoRiS is being developed using magnetic (Boozer) coordinates. In this paper, we present a benchmark of both codes, for a test geometry (one single magnetic island in W7-X) including full 3-D metric variations, solving for the strongly anisotropic electron licat conduction equation