Studies of laser-induced removal mechanisms for tokamak-like particles

The removal of metallic and carbon particles is a great issue in the framework of the ITER (International Thermonuclear Experimental Reactor) project. Indeed, the presence of these particles in the vessel of a tokamak leads to safety risks. The laser process seems to be a very promising solution for this cleaning. However, the process optimization requires a good knowledge of the removal mechanisms. For this purpose, we investigated the influence of beam parameters, such as laser pulse duration and wavelength, on the cleaning efficiency. In this paper, two kinds of particles are chosen to be studied, carbon aggregates and tungsten droplets, because they are typical of dust collected in tokamak. The results show an influence of beam parameters on the tungsten particles removal efficiency (PRE), whereas this influence is not significant for carbon particles. To help the understanding of the removal mechanisms, substrates and particles were inspected by scanning electron microscopy, before and after the irradiation. We will see on this paper that even if carbon and tungsten particles strongly absorb the different laser wavelength used, the removal mechanisms of these particles are very different.