Investigation of the Effects of Heating in CO2 on the Oxide-Coated Cathode Surface Microtopography and Emission Characteristics of a Triode Electron Tube

Abstract

A process which causes repeatable microtopographical changes in the oxide cathode coating of an electron tube has been investigated. This process, which is carried out by heating the cathode in CO2, reduces surface roughness and the incidence of loose particles. The scanning electron microscope in conjunction with electrical measurements was used to document and assess the repeatability of these microtopographical changes in the cathode and the resulting changes in electrical performance. Increasing the time of heating (contact time) in CO2 from 1 to 30 rain was found to increase the degree of microtopographical change but also to decrease the triode pulse emission. CO2 treatment leaves the Richardson work function of the cathode unchanged at ∼ 1.1 eV, indicating that no significant, change in the chemistry of the cathode was caused by this treatment. The lower emission capability after CO2 treatment was due to decreased values of the Richardson constant. The change is logically attributable to the observ...