Electron emission at the rail surface

The processes by which current is transferred from the cathode rail to the plasma armature in an arc-driven railgun are examined. Three electron emission mechanisms are considered, namely thermionic emission, field-enhanced thermionic emission (or Schottky emission), and photoemission. Calculations show that the dominant electron emission mechanism depends, to a great extent, on the work function of the rail surface, the rail surface temperature, the electric field at the rail surface, and the effective radiation temperature of the plasma. For conditions that are considered to be typical of a railgun armature, Schottky emission is the dominant electron emission mechanism, providing current densities of the order of 10⁹ A/m²