Unipolar Arc Tracks on Stainless Steel

Craters caused by unipolar arcs on stainless steel depend strongly on surface conditions. There are three diameter distributions: Small craters (～ 0.3 μm) for oxidised surfaces, larger craters (～ 2 μm) for moderately cleaned areas, and very large craters (～ 20 μm) for clean surfaces. These values are compatible with Joule heating models of crater formation. Compared with other metals of interest, stainless steel shows the largest craters.