Formation of hot spots and arc ignition on tungsten with nano-tendril bundles under high-density hydrogen plasma exposure.

Nano-tendril bundles (NTBs) are clusters of fuzzy nanostructures that form on tungsten surfaces when they are exposed to helium plasmas under specific conditions, reaching lengths of over 100 µm. Tungsten samples with NTBs and fuzz were exposed to high-density hydrogen plasmas in the Upgraded Pilot-PSI linear plasma device to investigate their response, with a particular focus on unipolar arc ignition and hot spot formation. Although NTBs are prone to arcing due to their high field electron emission characteristics, unipolar arcs have never occurred on NTBs.

Growth origin of large-scale fiberform nanostructures in He-W co-deposition environment.

When tungsten (W) is deposited with helium (He) plasma (He-W co-deposition) on W surface, enhanced growth of fiberform nanostructure (fuzz) occurs, and sometimes it grows into large-scale fuzzy nanostructures (LFNs) thicker than 0.1 mm. In this study, different numbers of mesh opening (apertures) and W plates with nanotendril bundles (NTBs), which are tens of micrometers high nanofiber bundles, were used to investigate the condition for the origin of the LFN growth.