High heat load experiments for first wall materials

Plasma disruptions in tokamaks lead to high energy deposition for short times on the first wall. Melting and evaporation processes on the first wall decrease the structural integrity of this component because of reduction of thickness and initiation of cracks, leading to a shortening of the life time of the first wall. This experimental study is focussed on the melting, evaporation and resolidification behaviour dependence on energy density, using a neutral beam injector (beam energy: 120 keV) on a 10 MW test stand. Specimens tested were SUS 304, SUS 316. PCA (primary candidate alloy): Al, Cu. C and Mo-coated copper alloys, which are expected to be used for components. The pulse length was varied from 20 ms to 250 ms (1.6 MJ/m² to 20 MJ/m²) at a constant heat flux of 80 MW/m. Metallographic analyses of the melted zone were carried out by SEM and XMA. Effects of one shot and multi shots on the melt layer thickness and evaporation loss were also studied.