Resistivity and power input in the cesium discharge at high current density

Measurements have been made of the potential gradient and the ion current to the tube wall in a tube 5 mm in diameter for current densities ranging from 5 to 20 amp/cm 2 and vapor press ures from 0.0045 mm to 0.33 mm. Potential gradients have also been measured in a I-mm tube for current densities ranging from 30 to 150 amp/cm 2 and vapor press ures from 0.33 to 2 mm. Published results give electron concentrations and temperatures for this range of conditions. The resistivity agrees approximately with the theoretical value for a completely ionized gas. The power dissipation comes predominantly from wall recombination at low pressures. Above 0.17 mm the radiation is appreciable, and above about 1 cm the radiation would account for most of the power input. Theoretical equations are given for the case where pressure and degree of ionization are so high that the vapor is opaque .