In situ method for studying stresses in a pulse-heated tungsten plate based on measurements of surface curvature

Abstract

Damage of divertor tungsten tiles as a result of transient plasma processes is one of the key problems of the ITER tokamak. Even if the temperature of the divertor tiles is maintained below the melting threshold, their thermal deformation, accumulation of residual stresses and cracking will occur. Cracking reduces the resistance of the metal to subsequent loads, therefore, the study of this process is important. In materials science, non-destructive methods for measuring mechanical stresses are very limited. In this work, a new method is proposed that allows non-contact investigation of stresses in polycrystalline tungsten plates by their bending. A corresponding diagnostic system and theoretical model are implemented. A number of experiments were carried out using this diagnostic system at the BETA facility at the Budker Institute to study the dynamics of tungsten plates bending with different thickness, subjected to pulsed heating of different intensities. The experimental results showed the qualitatively expected process of the plate bending, as well as good agreement with the theoretical model. This proved that the method described in the work is promising for use in order to study the residual stresses in a pulse-heated metal sample.

Keywords

• Tungsten
• Transient heat load
• In situ diagnostics
• Residual stress