A high-emission-density cathode for use in ultrahigh-resolution cathode-ray tubes

Surveillance for National Defense demands the utmost resolution in cathode-ray display tubes. In the development of such a tube, a need arose for an electron source with a continuous emission density capability beyond the present state of the art. Utilizing a newly developed dispenser cathode system, a miniature emitter with an area of cm²(0.010 inch in diameter) has been achieved, which is capable of 10 amperes per square centimeter, steady state, at a true temperature of 1000°C or lower. The critical aspects and parameters in the composition and processing of the basic cathode material and in the fabrication of the miniature cathode are reviewed. Results of evaluations of the miniature cathode in sealed-off glass tubes, representing cathode-ray tube environments, and in ion-pumped systems will be discussed. Emission constants and life test results as well as studies of migration of emission material over the surface adjacent to the cathode, using a projection microscope will be described.