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

The material erosion during disruption events will have significant impact on the lifetime of the plasma-facing components in future thermonuclear fusion reactors. At deposited energy densities of up to 10(7) Jm(-2) the resulting material erosion can reach values of several hundred microns per event. Under favourable conditions a cloud of the ablation 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 relevant energy densities have been applied with pulse durations of several ten mu s; typical beam diameters are in the order of 2 cm. Nevertheless, rather effective shielding phenomena could be demonstrated using test specimens made from metals and carbon-based materials. Beside profilometry and weight loss measurements for the determination of the material 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 and structural changes of the eroded surface.