Accelerated/reduced growth of tungsten fuzz by deposition of metals

From the helium (He) plasma irradiations to tungsten performed in the Magnum-PSI device, the effects of deposition of metals on the helium-plasma induced fiberform nanostructures (fuzz) are discussed. It was found that fuzz was not formed at the center of the plasma cylinder if there were significant metallic impurities from the source. Deposition of metallic impurities (mainly molybdenum and copper) counteracted the growth of fuzz. In addition to the effects of metals from the source, we installed a sputtering source near the sample to replicate the deposition environment in fusion devices. The thickness of fuzzy layer was ∼7 µm, which was about five times greater than that without deposition, at the He flux of 1.3×10²⁶ m⁻², suggesting that the growth rate of fuzz layer was significantly accelerated due to the deposition of tungsten.