Extended test results from scandia-doped tungsten dispenser cathodes

Abstract

Spectra-Mat, Inc scandia-doped tungsten powder and matrices were tested up to 19,500 hours with minimal increases in kneepoint temperature at 5 A/cm2 emission density. Cathodes were run in an accelerated life test, 100°C above the kneepoint. Data from all cathodes show consistent emission at 5 A/cm2 at or below ~900°C during the testing. Spectra-Mat has continued the development process to create powders of larger size, such that current (and routine) brazing and sintering operations might be available for processing scandia doped tungsten materials, minimizing the development of new methods for all size cathodes.