Molecular dynamics analysis of self-sharpening phenomenon of thin electrode in single discharge

A self-sharpening phenomenon of thin tungsten electrode was found in single discharge under the specified conditions of discharge current and pulse duration. The needle-like sharpening occurs in the period of 100 to 300 μs after the end of discharge when the thin electrode is negative polarity. To understand the mechanism of the self-sharpening phenomenon, molecular dynamics (MD) computer simulation is carried out. MD simulation suggests that the essential conditions for self-sharpening are to exert large radial external force and to produce thin molten layer on electrode surface. The optimum conditions in pulse duration and discharge current exist for self-sharpening depending on the thermal conductivity and size of the electrode.