Erosion behavior of actively cooled tungsten under H/He high heat flux load

Abstract

We devised a method to measure erosion in the micrometer range on actively cooled tungsten samples. The method is based on applying micrometer-sized markers onto the side faces of the samples using a focused ion beam. With this method we measured the erosion of tungsten samples exposed to a hydrogen beam with 6% helium content. At 10.5 MW/m² the samples were exposed to particle fluences between 2•10 25 m -2 and 7•10 25 m -2 . Up to 630 pulses with a pulse duration of 30 s were employed. The actively cooled samples reach an equilibrium surface temperature which was varied from about 600°C to 2000°C. We find an amount of erosion which clearly exceeds the value computed from physical sputtering yields by roughly a factor of two. This is possibly correlated with the formation of a complex nanometer-sized morphology, which was observed for all temperatures.

Surface morphology changes of tungsten exposed to high heat loading with mixed hydrogen/helium beams

“…An equilibrium is reached between surface erosion and bubble formation and the thickness of the affected layer is nearly constant above a fluence of 1 Â 10 25 m À2 . We note that the thickness of the affected layer, compared with the 6 at.% He loading, decreases from 400 ± 100 nm to about 250 nm in case of the 1 at.% He loading [9,10] at constant total fluence. Further, we observed the same surface-and bubble layer structures independent of the surface temperature in the investigated temperature range between 1000°C and 2000°C.…”

“…The applied loading conditions were similar to the previously performed experiments where a particle composition of 94 at.% H and 6 at.% He was used [9,10]. The experiments were performed at 10 ± 0.5 MW/m 2 central heat flux and pulses of 30s duration to ensure the comparability of the results.…”

Tungsten erosion under combined hydrogen/helium high heat flux loading

“…A detailed description of the method and analysis tools as well as the original publication of the erosion data can be found in [13].…”

In Situ Renewable Coating of Boron Carbide (B4C) for Plasma Materials for Plasma-Technological and Fusion Devices

“…Investigations showed that near stoichiometric B 4 C coating can be deposited in high-temperature plasma providing total dissociation of the molecules of initial substance. The conclusion was confirmed experimentally, when B 4 C coating had been successfully deposited in plasma devices (PISCEC-B [5] and tokamak T11-M [6]). The vapor of nontoxic, nonexplosive, and nonhazardous carborane (C 2 B 10 H 12 ) was used as the initial substance for coating deposition in the course of regular discharge in the plasma devices.…”