Surface Morphological Features of Molybdenum Irradiated by a Single Laser Pulse

Abstract

Molybdenum (Mo) is considered a plasma facing material alternative to tungsten (W) for manufacturing the divertor armours of International Thermonuclear Experimental Reactor (ITER). Transient thermal loads of high energy occurring in a tokamak during the service life have been simulated through a single laser pulse delivered by a Nd:YAG/Glass laser, and the effects have then been examined through scanning electron microscopy (SEM) observations. An erosion crater forms in correspondence with the laser spot due to the vaporization and melting of the metal, while all around a network of cracks induced by thermal stresses is observed. The findings have been compared to results of similar experiments on W and literature data. The morphology of the crater and the surrounding area is different from that of W: the crater is larger and shallower in the case of Mo, while its walls are characterized by long filaments, not observed in W, because the lower viscosity and surface tension of Mo allow an easier flow of the liquid metal. Most importantly, the volume of Mo ablated from the surface by the single laser pulse is about ten times that of W. This critical aspect is of particular relevance and leads us to conclude that W remains the best solution for manufacturing the armours of the ITER divertor.

Characterization of KrF Excimer Laser Ablation of Cadmium in Different Liquids for Biomedical and Industrial Applications

“…The presence of pores on the irradiated material surface will be converted into bubbles after melting. The transition of a solid into a liquid phase causes the generation of nanobubbles in liquids and produces cavities with sizes regarding inter-atomic spacing equivalent to numerous angstroms [29].…”

“…The concentration of these voids is about 10 18 cm −3 in normal conditions [30]. Laserpulsed heating results in the increase of bubble growth which enhances the ejection of microdroplets and generation of microcavities/craters [29].…”

Grain Orientation and Hardness in the Graded Interlayer of Plasma Sprayed W on CuCrZr

“…Therefore, they must have a high melting point, excellent thermal conductivity, low activation under neutron irradiation, and very low physical sputtering and tritium retention [3]. Among all the plasma-facing materials (PFMs) considered for building armors, W is the most promising [4][5][6][7][8][9], even though some of its problems are not yet completely solved (e.g., see the review of Linsmeier et al [10]).…”

Surface Morphology of Refractory Metals Submitted to a Single Laser Pulse

“…This work compares and discusses the behavior of some high-Z refractory metals of fusion interest, namely bulk W, W obtained by plasma spray (W-PS) [14][15], W-1%La2O3 [16] and Mo [17] by simulating transient events through laser irradiation. The materials have been submitted to a single laser pulse in the same experimental conditions and the effects have been studied through scanning electron microscopy (SEM) observations.…”