Simulations of Explosive Electron Emission in Cathodic Arcs

Explosive Electron Emission (EEE) is typical to cathodic arcs. The physics of multi-phase phenomena associated with self-sustained formation of explosive emission centers (ectons) is not fully understood. This SBIR project will conduct experimental, theoretical, and computational studies of EEE-induced phase transitions at electrode surfaces and formation of plasma jets in cathodic sparks and arcs in rare and reactive gases for different gas pressures and currents. Experimental studies will be conducted at LBNL to understand effects of gas type and pressure on ecton formation and dynamics. CFD Research Corporation (CFDRC) will enhance its recently developed adaptive kinetic-fluid simulation tool for computational studies of EEE processes. This project will investigate effects of background gases on near-electrode phenomena and phase transitions between gas, liquid, and solid states during electrical breakdown and formation of arc discharges. After completing Phase II, a new multi-physics computational tool with advanced capabilities will be available for fundamental studies and industrial engineering of plasma systems utilizing arc discharges. Cathode processes involving localized, non-stationary centers of plasma generation are relevant to many fields of science and industry, including processes on the walls of plasma fusion facilities and industrial scale fabrication of hard and wear-resistant coatings on tools and engines, high power switches, and welding equipment. The difficulties of understanding cathode processes are related to the presence of several phases (solid, liquid, gas and plasma) and fast dynamic changes down to the nanosecond time scale. This project will further understanding of near-electrode phenomena in gas discharges and offer a computational tool with breakthrough capabilities for analyzing plasma- surface interactions in cathodic arcs. The developed tool will be used to understand unipolar arcing in fusion devices, the formation of microcraters and ejection of liquid droplets associated with electrode erosion in cathodic arcs. The project will clarify effects of background gases on ecton formation in arcs with liquid and solid electrodes. The developed computational tool will be used by scientists and engineers for studies of arcing on plasma-facing components in fusion reactors, as well as pulsed- power, e-beams, X-rays and other applications utilizing cathodic arcs.