Arc ignition and hot spot formation on tungsten with nano-tendril bundles under hydrogen plasma exposure

Tungsten surfaces with Nano-tendril bundles (NTBs), a collective group of fibrous nanostructures which forms isolated and grow up to tens of microns, are exposed to high density hydrogen plasmas. Under the conditions in which sheath thickness are comparable or smaller than the size of NTBs’, with negative biasing voltage, the NTBs presented bright emission due to concentrated heating by incident ions, leading to the formation of hot spots. At the same time, arc traces are observed on the surface, but far from the NTBs area, suggesting that the concentrated heat load precedingly degrades NTB’s tip, lowering the local field emission and hence arc ignition probability.