Conformal plasma cathode for surface hardening of metals

A broad-area impulse electron beam of 10⁵-10⁶ electron volt energy and 100-1000 A/cm² 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 10¹²-10 ¹⁴/cm³ is required