Calculation of the radial tungsten transport in cylindrical gas-filled incandescent lamps

Abstract

The rate of tungsten transport in a cylindrical gas-filled incandescent lamp has been calculated. The theory is based on the assumptions of Langmuir and Fonda. In this model the transport has been determined by the rate of diffusion through the stationary Langmuir zone. The diameter of that zone has been calculated according to the method of Elenbaas. In the present method the position dependence of the diffusion coefficient is introduced. A result is that the rate of tungsten transport as a function of the envelope diameter has a minimum. The inner envelope diameter is then equal to that of the Langmuir zone. The theory gives also an easy method of calculating the working pressure of the inert gas from the filling pressure.

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