W-1% La2O3submitted to a single laser pulse: Effect of particles on heat transfer and surface morphology

W-1% La2O3 has been irradiated by a single laser pulse (lambda = 1064 nm, pulse duration tau approximate to 15 ns, pulse energy Ep approximate to 4 J, spot size Phi = 200 mu m, surface power density I = 8.5 x 10(11) W.cm(-2)) to simulate the effects of transient thermal loads of high energy occurring in a tokamak under operative conditions. The samples have been then examined by scanning electron microscope (SEM) observations to investigate erosion effects and surface morphological features. A surface depression forms in the spot central area surrounded by a ridge due to the movement of molten metal. Owing to the burst of gas bubbles, hemispherical cavities of about 10 mu m and deposited droplets are observed in the ridge while the zones surrounding the ridge thermal stresses arising from fast heating and successive cooling produce an extended network of micro-cracks that often follow grain boundaries. The results are discussed and compared to those obtained in a previous work on pure bulk W.