Thermo-mechanical investigation of the new solid tungsten divertor tile for special purposes at ASDEX upgrade

Abstract

A new solid tungsten divertor for the fusion experiment ASDEX (Axial Symmetric Divertor EXperiment) Upgrade is under construction at present. For special purposes of the plasma diagnostic in the divertor region a special formed solid tungsten divertor tile is required. A so-called Langmuir probe is used to determine the ion temperature, ion density and ion potential of the plasma. With the aim to place the probe on the right position some of the divertor tiles (9 at the device circumference) have been adequately adapted. This paper discusses the main results of the numerical analysis of the thermo-mechanical behavior under heat load. Primary, the elastic-plastic calculation was applied to analyze thermal stress and the observed elastic and plastic deformation during the heat loading. The influence of a possible material degradation due to thermal cracking was studied. Additionally, the knowledge gained by the numerical analysis was used for the shape optimization of the divertor tile. The first results from the numerical life cycle analysis of the tungsten tiles are reported. Finally, based on the knowledge gained by the numerical analysis, in the light of problem complexity, it is recommended to perform some additional thermal tests. These tests should be performed with the aim to increase the reliability of the special shaped tungsten tile during operation.