Modelling of the material vaporisation during a plasma disruption taking into account the influence of a magnetic field

In ITER fusion reactor the central plasma is confined by helical magnetic field lines. The most external field lines have open configuration and reach the divertor plates with a certain inclination. During hard disruptions a large part of the energy of the central plasma is dumped along the magnetic field lines and results in melting and vaporization of the divertor solid material (ablation is caused in case of graphite divertor). The produced vaporized material cloud protects the divertor from direct interaction with the disrupting plasma (vapour shield effect). Only a small fraction of the impinging beam energy reaches the solid plate and therefore the damage to the plasma facing component is reduced. The amount of energy reaching the divertor surface depends on the physical properties of the vapour shield, i.e. its density and temperature. In order to quantify the erosion of the divertor plates and therefore its lifetime, the magneto-hydrodynamic behaviour of the expanding divertor material cloud has to be described. Therefore the 1-dimensional Lagrangian radiation magneto-hydrodynamic code FOREV-1 was extended to a two components MHD code in which the modelling of the magnetic field effects on the expanding material cloud was carried out by taking into account that the magnetic field is oblique to the target (1 1/2-dimensional model). In this model two components of the magnetic field and of the expansion velocity (perpendicular and parallel to the target) are calculated as function of time and space. The theoretical and numerical models used in the new version of FOREV-1 have been validated with experimental data, and the MHD-model has been tested by comparison with a self-similar model. Both the comparisons with experiments and with the self-similar model have shown a good agreement. Finally calculations have been done assuming ITER load conditions and beryllium and graphite divertors. (orig.)