Studies on grid emission

Primary grid emission of various grid materials exposed to the evaporation products of "L," impregnated, oxide-coated, and thoriated tungsten cathodes is discussed. The work function of a tungsten grid exposed to the evaporation products of the four types of cathodes varies from 1.2 to 2.0 ev, the final value depending upon the past history of the cathode, namely, the nature of the surface of the grid and the temperature and length of exposure to the cathode. A detailed discussion of the performance of titanium, which exhibits excellent grid emission inhibiting properties, is included.