Investigation of dust formation during changes in the structural and surface properties of plasma-irradiated materials

Abstract

• The contribution of surface defects (cracks, craters, bubbles) and structural changes (recrystallization) exposed by the plasma beam candidate materials to dust formation is studied. • The scanning electron microscopy (SEM), and elemental and X-ray diffraction (XRD) analysis were used to study the surface morphology, chemical composition, and crystal structure of plasma beam irradiated materials. • On the surface of tungsten target the well-developed micro-cracks are formed, and defects such as melting and flaking of the surface layer, drop-shaped structures formation are also observed. The increasing of the pulse dose led to an increase in the width and depth of these microcracks. • Tungsten target erosion (mass loss) occurs due to the ejection of particles from the tungsten surfaces, both as droplets and as solid dust during crack development. • The measured peak shift in carbon was 0.03 degrees after x5 plasma load. Thereby, carbon is generally more resistant to plasma beam impact than tungsten. This paper presents the results of studying the impact of a plasma beam during the interaction of divertor candidate materials in a coaxial plasma accelerator, where graphite and tungsten plates were used as candidate materials. The authors consider the contribution of surface defects (cracks, craters, bubbles) and structural changes (recrystallization) in candidate materials to dust formation under the action of a plasma beam. The other aspect studied in the paper is the erosion of copper substrates (nearby components) under the action of a hot target dust cloud with account for the kinetic influence of hot dust particles on nearby components. It should be noted that these particles are formed by the erosion of the material by the plasma beam. Scanning electron microscopy (SEM), elemental and X-ray diffraction analysis (XRD) were used to study the material surface morphology, chemical composition, and crystal structure. The authors also consider some undesirable effects revealed after irradiation of divertor candidate materials. The obtained experimental results will be useful for evaluating the prospects for further application of these materials in existing and future fusion reactors (e.g., in the international fusion reactor ITER).