Studies on grid emission

This paper is concerned only with the study of primary grid emission of various types of grid materials resulting from the evaporation products of L, impregnated, oxide-coated, and thoriated tungsten cathodes. The factors contributing to grid emission are analyzed. A detailed discussion of the performance of titanium, which exhibits excellent grid emission inhibiting properties, is included. In our investigation a planar triode construction was used, the grids of which consisted of a two-terminal loop of 0.010 inch diameter wire. In the assembly and processing utmost precautions were taken to insure minimum contamination of the various elements. The methods of assembly and processing are fully described in the paper. These tubes were tested using pulsed and dc techniques, and a discussion of the testing methods is included. The work function of a tungsten grid exposed to the evaporation products of the L, impregnated, and oxide-coated cathodes varies from 1.2 to 2.0 ev, the final value depending upon the past history of the cathodes, namely, the nature of the surface of the grid and the temperature and length of exposure to the cathodes.