THE EFFECT OF EMITTER WORK-FUNCTION PATCHES ON THE PERFORMANCE OF CESIUM THERMIONIC CONVERTERS,
Abstract
An experimental program to obtain the currentvoltage characteristics of a metal cesium thermionic converter with a monocrystal molybdenum emitter showing the (110) crystallographic face to cesium vapor is described and the results are presented. It is shown that the continuous linear increase in output current with decreasing output voltage or, in other words, the fact that the emission current does not show a sharp saturation valve, may be due to patches of different work function on the emitter surface. It is shown that an exponential Boltzmann distribution might be expected to describe the variation in work function over the emitter surface. Also, this Boltzmann distribution may account for the shape of the current-voltage characteristics obtained from a cesium thermionic converter with a monocrystal molybdenum emitter in the region of low output voltage. From the analysis of these characteristics, the percentage area with the exponential distribution is determined. The area of the exponential patch should increase as the coverage increases. Furthermore, the experimentally determined values of the patch area decrease linearly with increasing values of the ratio of emitter temperature to cesium reservior temperature, from which it is concluded that these patches may be caused by thermal excitation of the adsorbed layer on a nonuniform substrate. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1963
- Accession Number
- AD0420279
Entities
People
- John W. Gadzuk
Organizations
- Massachusetts Institute of Technology