Microstructure and defect analysis in the vicinity of blisters in polycrystalline tungsten

Highlights: • We have developed two reliable methods for preparing cross-section samples from W. • Electropolished bulk cross-sections allow dislocation imaging by SEM. • Precision electropolishing of FIB lamellae for TEM reduces FIB damage. • We applied both methods to W exposed to D plasmas or MeV W ions. • We demonstrate a clearly enhanced dislocation density in blister caps. - Abstract: Up to now, analyzing the production of dislocation-type defects in the subsurface region of plasma or ion-exposed tungsten samples has been hampered by the challenging production of suitable cross-section samples for transmission electron microscopy. We present two reliable methods based on precision electropolishing to prepare cross-sections of tungsten that allow direct imaging of dislocation-type defects by scanning as well as by transmission electron microscopy. Using these methods, we are able to demonstrate a clear enhancement of the dislocation density in the caps of blisters on tungsten exposed to H isotope plasma, i.e., of surface morphologies that are correlated to subsurface cavities. As a benchmark, we also show a cross-section of tungsten irradiated by 20 MeV W⁶⁺ ions.