DIVERTOR PLATE EROSION AND RADIATING VAPOR SHIELD FORMATION DURING HARD DISRUPTIONS - THEORY AND NUMERICAL MODELING

The time evolution of radiating vapour shields over eroding solid surf aces and the resulting erosion rates are modelled by one dimensional ( I-D) and 1 1/2-D resistive MHD codes. Graphite or carbonized divertor plates subjected to high energy deuterium plasma particles during disr uptions or giant ELMs are considered. The energy flux range assumed co rresponds to ITER, conditions. Various physical phenomena having a pri mary effect on the erosion rate, such as collisional interaction of th e energy carriers with the target (solid surface or vapour particles), electrostatic shielding, magnetohydrodynamic interaction and radiant energy transport, are investigated in detail. In the 1-D and 1 1/2-D a pproximations used and for the energy input parameter range considered (Q(0) = 10(11) W/m(2)) ablation rates of the order of 10(28)m(-2).s(- 1) were obtained. It is shown that processes, such as lateral expansio n, lateral drift, radiation losses through the lateral surfaces of the scrape-off layer (SOL) and the Hall effect, may notably change the pr edicted erosion rates and warrant a more elaborate, at least 2-D, trea tment of the problem.