Evaluation of thermionic emitter surfaces

Abstract

This paper describes an experimental evaluation of cesiated tungsten and cesiated rhenium thermionic emitter surfaces prepared by different methods. Two sorts of evaluation are presented. In the first, the average emission characteristics of these surfaces are described by graphs of cesiated work function φ vs the ratio of surface temperature T to cesium reservoir temperature T_R. Details of the work function distribution for certain surfaces are also obtained and related to the average characteristics. In the second method, surfaces are evaluated in terms of the electrical output of thermionic converters utilizing these surfaces as emitters (cathodes). For certain materials curves of power density, and of current density, vs. output voltage are presented, where each curve has cesium reservoir temperature and interelectrode spacing optimized, and emitter temperature appears as a parameter. Other curves show output power density as a function of emitter temperature, at specified output voltage and spacing.