A 2-D numerical simulation of ITER-FEAT disruptive hot plasma-wall interaction and model validation against disruption simulation experiments

The two-dimensional (2-D) radiation-magnetohydrodynamic (R-MHD) code FOREV- 2 was developed for modeling of disruptive hot plasma-wall interaction, for calculation of erosion by evaporation of the ITER-FEAT vertical divertor t arget, and for calculation of the impurity transport in the divertor. FOREV -2 uses a 21/2-D MHD model, a 2-D scheme for anisotropic radiation transpor t, and a solution of the magnetic field equations in the plasma shield for all three components of the magnetic field. Details of FOREV-2 with emphasi s on the MHD equations, the equations for the magnetic field, the vaporizat ion model, the angular dependent multigroup radiation transport, and the op tical properties of plasmas, and validation of FOREV-2 against analytical r esults are discussed. Moreover, disruption simulation experiments, performed at the plasma gun fa cilities at TRINITI Troitsk were used for validation of FOREV-2 and for inv estigations of the MHD of typical plasma shields. From the results of the n umerical analysis of the simulation experiments, it is concluded that turbu lence in the experimental plasma shields is absent and that the stability o f the cold and dense part of the plasma shields, which determines the targe t erosion, can be adequately modeled by FOREV-2 by use of the classical mag netic field diffusion coefficient. The experimentally observed downstream d rift of plasma shields along the surface of the vertical targets is due to the lateral motion of a cold and dense plasma layer close to the target. Th e observed upstream shift of the erosion profiles of vertical targets is du e to reradiation from the expanding plasma shield. Line radiation and an ap propriate model for anisotropic radiation transport are necessary for a rea listic calculation of the reradiation from carbon plasma shields. Moreover, inclusion of the line radiation allows one to get a realistic radiation co oling after switching off the heating. Target erosion in the simulation exp eriments is caused by radiation. The agreement between calculated and measu red erosion for graphite and quartz demonstrates the adequacy of the calcul ated 2-D radiative target heat loads. The 2-D numerical analysis of the disruption simulation experiments allows one to conclude that such experiments adequately simulate the tokamak plasm a shield properties and its dynamics. The extensive validation exercise of FOREV-2 against disruption simulation experiments gives confidence that the numerical analysis of erosion for the ITER-FEAT vertical targets during th e thermal quench phase of a disruption and the impurity production during E LMs and its transport toward the x-point to be performed with FOREV-2 is ba sed on sound principles and covers all important aspects of plasma shield b ehavior and plasma shield stability.