Self-consistent plasma-neutral modeling in tokamak plasmas with a large-area toroidal belt limiter

Abstract

Plasma-neutral phenomena in the edge plasma and scrape-off layer of the Torus Experiment for Technology Oriented Research [G.H. Wolf and the TEXTOR Team, J. Nucl. Mater. 122&123, 1124 (1984)] with the toroidal belt Advanced Limiter Test (ALT-II) [D.M. Goebel et al., J. Nucl. Mater. 162–164, 115 (1989)] are simulated using the code package B2-EIRENE [D. Reiter et al., Plasma Phys. Controlled Fusion 33, 1579 (1991)]. Spatially-constant, anomalous radial transport coefficients (D,V,χ) are used for fitting measured electron temperature and density profiles. Primary neutral fluxes are determined by plasma fluxes to material surfaces, and Dα emissions are predicted from them. Comparison of the predicted Dα emission with measurements indicates a critical need, in predictive modeling, for a self-consistent model of fluxes to material surfaces that are parallel to the magnetic field. Appropriate factors are calculated for deducing D+ source rates from Dα emissions measured in various locations, taking into account molecular processes and spatially varying plasma parameters; values range from 17 to 28 ions/photon. Ion fluxes lost to pumps or the wall must be explicitly re-introduced as neutral fluxes at the outer boundary.

Tokamak plasma edge modelling including the main chamber wall

“…On the other hand, a flexible introduction of limiters and baffling structures was already incorporated in B2 by Baelmans et al [14,22] for TEXTOR ALT-II limiter simulations by manipulating the corner points in the solid region and thus the last grid cell near the boundary only (see figure 2). In the left figure the original grid is shown together with the position of the vessel wall and the resulting movement of grid points in the solid region (arrows).…”

2D edge plasma modeling extended up to the main chamber

“…An alternative, and more accurate method followed in the present paper, basically refining the "staircase target" concept to handle the inclined surfaces, was reintroduced in B2 [5,6] for TEXTOR ALT-II limiter configurations. This method only distorts the final grid cells directly facing the plasma-wall interface, see Fig.…”

Edge plasma modelling for HT-7 superconducting tokamak experiments

“…In previous modelling for limiter tokamaks, for example TEXTOR, by using B2 code [8,9], Carre is not applied to the computation mesh production, the computational meshes are generated by an analytic method. With the analytic method the conformal transformation is used, by choosing the free parameters according to the limiter geometry in the device the computational meshes can be generated.…”