EROSION OF METALS AND CARBON-BASED MATERIALS DURING DISRUPTIONS - SIMULATION EXPERIMENTS IN PLASMA ACCELERATORS

The material erosion during disruption events will have significant im pact on the lifetime of the plasma-facing components in future thermon uclear fusion reactors. At deposited energy densities of up to 10(7) J m(-2) the resulting material erosion can reach values of several hundr ed microns per event. Under favourable conditions a cloud of the ablat ion vapor forms in front of the plasma-facing component which shields part of the incident energy flux. To verify this effect experimentally in disruption simulation tests fusion-relevant conditions can be met best in so-called plasma accelerators. In the VIKA device ITER relevan t energy densities have been applied with pulse durations of several t en mu s; typical beam diameters are in the order of 2 cm. Nevertheless , rather effective shielding phenomena could be demonstrated using tes t specimens made from metals and carbon-based materials. Beside profil ometry and weight loss measurements for the determination of the mater ial erosion a variety of post-mortem analyses (e.g. scanning electron microscopy, energy dispersive X-ray analysis, metallography) have been applied to investigate resolidification processes in the melt layer a nd structural changes of the eroded surface.