Surface modification and droplet formation of tungsten under hot plasma irradiation at the GOL-3

Comparison of tungsten modification after irradiation at different facilities for PSI studies

“…Under small loads (less than 0.2 MJ/m 2 ), the primary erosion mechanism is physical sputtering, and thus the erosion is acceptably small (after irradiation at the open trap GOL-3 [2] and electron beams facility JUDITH-2 [3]). …”

“…Bubbles and three different crack networks with typical cell sizes of 1000, 10 and 0.3 µm were detected after irradiation of the tungsten surface by different methods (after irradiation at the Nd:YAG laser [4], QSPA Kh-50 and GOL-3 [6], [10], PSI-2 [7], Nd:YAG laser, JUDITH-1 and GOL-3 [2], [8] [11]. The typical erosion depth is less than 20 μm [2], [10]. The thickness of the remelted layer was ~ 35 μm [2].…”

“…The typical erosion depth is less than 20 μm [2], [10]. The thickness of the remelted layer was ~ 35 μm [2]. The type of the melted layer fracture can be described as a classic one with low energy of intergranular binding.…”

“…The type of the melted layer fracture can be described as a classic one with low energy of intergranular binding. The main volume of the tungsten sample, which did not undergo melting, shows signs of river patterns, typical of cleavage fracture with areas of intergranular fracture [2]. The newly formed crystals (cell size about 10 µm) have a typical columnar structure of molten material due to intense heat transfer to the internal layers of the tungsten sample.…”

“…Crack networks with sizes of 0.3 µm are attributed to the formation of individual crystallites [10]. With loads of 4 MJ/m 2 (corresponding to unmitigated ITER type I ELMs), a frozen melt is formed on the tungsten surface instead of crack networks with cell sizes of 1000 µm (GOL-3 [2], [10]). Big droplets, deep bubbles and waves were found on the tungsten surface.…”