Spontaneous plasma formation via electrical explosion of nanostructured metal surface layers in plasma-surface interactions

The article is aimed at studying the issue of spontaneous, i.e., triggerless ignition of arcing plasma splashes due to explosive-electronemission pulses at fiber-form nanostructured (W-fuzz) surface during plasma-surface interaction. There has been proposed an equivalent sputtering yield for arcing Y-eff = 4.8 gamma C/mg, where gamma is the rate of plasma production (mass per charge) from a cathode by vacuum arc discharge. The ratio of the released-to-incident atoms Y-eff can reach the value of about 10 for the plasma production rate of 2 mg/C. The increase in the plasma production rate gamma has been estimated as (i) an increase in mass due to mechanical destruction of neighboring nanofragments and (ii) a decrease in ions average charge. The resulting twentyfold increase in gamma at few-mu m layers agrees with the experimental observations. The critical temperature T-cr (and corresponding cohesive energy E-coh = 5 T-cr) for the W-fuzz nanostructure has been estimated as T-cr = 2 n/n0 eV, where n/n0 is the relative density of the W-fuzz nanostructure. It falls below 1 eV for typical fuzz layer thickness larger than few tenths of mu m. This results in the experimentally observed reduction of the average W-ions charge in vacuum arc plasma. Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0158993