Damage to preheated tungsten targets after multiple plasma impacts simulating ITER ELMs

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

“…For example, let us compare irradiation conditions in GOL-3 [20] and QSPA Kh-50 [6], [14]. Parameters of the energy loads of plasma stream for the GOL-3 long pulse accelerator [9], [20], [21] are very close to the QSPA parameters: a pulse duration of up to 0.3 ms and energy loads of up to 2.5 MJ/m 2 .…”

“…Under loads of about 0.5 MJ/m 2 , the tungsten surface did not melt, but after multiple plasma impacts crack patterns are formed (found after irradiation by using Nd:YAG laser [4], [5], quasi-stationary plasma accelerators QSPA Kh-50 [6], linear plasma machines PSI-2 [7], Nd:YAG laser, JUDITH-1 and GOL-3 [8], [9]). …”

“…At the QSPA Kh-50 plasma gun, a load 0.75 MJ/m 2 is above the melting threshold [6], but the surface did not melt after electron beam irradiation with the same load [9].…”

“…With loads of 1-2 MJ/m 2 (corresponding to mitigated ITER type I ELMs), the tungsten surface melts, and the loads exceed the evaporation threshold [6]. 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].…”

“…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].…”