Radiation Absorption Effects in B2-EIRENE Divertor Modelling

The 2D tokamak edge plasma simulation package B2-EIRENE has been upgraded with a model incorporating the effect of Lyman series photon trapping and ionization from photo-excited states. The numerical approach is based on Monte-Carlo sampling of photon trajectories and a collisional-radiative model for the effective ionization rate. A series of calculations with self-consistent solutions for the neutral gas, photons and plasma background was carried out for ITER edge plasma parameters. It was found that the extra ionization source in the model leads to a higher plasma density near the targets, and is balanced predominantly by enhanced volume recombination. Despite significant changes in the divertor dynamics due to photon trapping the main “engineering scalings” for ITER operational parameters (e.g. peak heat fluxes vs. divertor gas pressure) show no significant modification. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)