THERMIONIC VACUUM TUBES 



33 



the thermionic emission of tungsten, and thoriated tungsten when 

 freshly activated, do not vary much between different samples, they 

 are given with sufficient accuracy for tube design purposes by single 



f.003 INCH WIRL 

 OPERATED AT X 



B a B o 



5^ 



TEST N? 



O o o o 

 P o o <o 

 <0 ro - TUBE NS 



§ 8SSSI I CONSTANT* 



YYATTS x 10 

 POWER-EMISSION CHART 



Fig. 1 



lines. Coated filaments, however, show a rather wide variation as is 

 indicated. The range of variation shown in Fig. 1 was obtained in 

 the study of several thousand tubes; 10 per cent, showed activity 



