Effect of a Temperature Gradient on Thermionic Emission

Abstract

The effect of a temperature gradient at the surface of a metal on the thermionic emission current is calculated. The calculation is motivated by current research in which metal surfaces are exposed to high-intensity optical maser beams with a consequent heating of the surface. A Sommerfeld free-electron model of a metal is used in which the temperature of the metal is allowed to be a function of position. A modified distribution function for the electrons is calculated using the Boltzmann transport equation from which the thermionic current is obtained. Approximations are made that limit the theory to small changes in the distribution function but the results are valid for realizable experimental conditions. It is shown in an example that for Q-switched laser intensities observable effects can be expected.