Conformal plasma cathode for surface hardening of metals

A broad-area impulse electron beam of 10/sup 5/-10/sup 6/ electron volt energy and 100-1000 A/cm/sup 2/ current density can almost instantaneously heat treat carbon steel surfaces to achieve high hardness. The characteristics of a plasma cathode that forms such an electron beam conformally with the surface of the treated object are described. Forming such a plasma cathode requires that the voltage drop across the anode sheath dominates over the voltage drop across the cathode sheath. High-density cathode emission and a ratio of cathode surface area to workpiece surface area of at least 10 are necessary to drive the anode sheath to assume such a dominant role. A fully ionized plasma of density near 10/sup 12/-10/sup 14//cm/sup 3/ is required.