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TEMPORARY THERMAL FLUCTUATIONS ON THE CATHODE SURFACE AND THEIR INFLUENCE ON SWITCHING OF THE CATHODE WORKING MODE

M. Cristea1,*

Affiliation

  1. “Politehnica” University of Bucharest, Department of Physics, Splaiul Independentei 313, 060042 Bucharest, Romania

Abstract

The aim of this paper is to investigate the effect of a thermal fluctuation on the emissive active cathode zone. Function of various external conditions, like current intensity, electrodes shapes and surface electrode non-homogeneities, the electrode functioning mode can be diffuse or hot-spot. The two modes are extremely different from the evaporation and sputtering of the emissive layer point of view. In the diffuse mode, the surface temperature distribution is relatively constant and low. The vaporization rate of the barium layer is small. Contrary, in the hot-spot case, the local core temperature of the spot can be higher than of the tungsten melting point temperature (3663 K) and the activator layer is rapidly destroyed. This allows to the lamp lifetime reduction. From this point of view is more convenient to have an electrode operating in diffuse mode. In this work are analyzed what happens with a local thermal fluctuation due to the current discharge pulse superposed on the current injected by the source supply. Are found the conditions when the cathode operation mode passes from diffuse to hot-spot mode and also the conditions when the fluctuations are dumped in time..

Keywords

Field-enhanced thermionic emission, Diffuse and hot-spot mode, Switching process.

Submitted at: Jan. 12, 2005
Accepted at: Sept. 22, 2005

Citation

M. Cristea, TEMPORARY THERMAL FLUCTUATIONS ON THE CATHODE SURFACE AND THEIR INFLUENCE ON SWITCHING OF THE CATHODE WORKING MODE, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 5, pp. 2435-2441 (2005)