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

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 $\mathrm{(D,V,\chi )}$ are used for fitting measured electron temperature and density profiles. Primary neutral fluxes are determined by plasma fluxes to material surfaces, and $\mathrm{D\alpha }$ emissions are predicted from them. Comparison of the predicted $\mathrm{D\alpha }$ 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 ${\mathrm{D}}^{+}$ source rates from $\mathrm{D\alpha }$ 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.