Abstracts of Technical Articles from Bell System Sources 



The Emission of Secondary Electrons from Tungstev} A. J. Ahearx. 

 An apparatus is described for investigating critical potentials in the 

 emission of secondary electrons from tungsten. Measurements on the 

 velocity distribution in the primary beam show that secondary elec- 

 trons from the electron gun are absent. Tube characteristics which 

 might introduce spurious critical potentials in the secondary emission 

 from tungsten appear to be absent. By heat treating the tungsten 

 and cleaning up residual gases, maxima and critical slope changes were 

 developed below 40 volts. With sensitive methods of measuring and 

 plotting the data, critical potentials within the range from 40 to 500 

 volts were observed only at the following uncorrected voltages: 70, 

 108, 208, 297 volts. All but the 70-volt effect disappeared eventually 

 after heat treatments of the tungsten target. Thus when the tungsten 

 surface is most free from contamination, critical potentials persisted 

 only at the following uncorrected voltages: maxima at about 3.5 and 

 8 volts and slope increases at 24, 33 and 70 volts. The phenomena 

 may be associated with the diffraction of electrons or the production 

 and absorption of characteristic soft x-rays. Regardless of the 

 mechanism operating at the critical potentials, their decrease or 

 elimination beyond 40 volts points strongly to effects of surface 

 contamination rather than to characteristics of tungsten. 



Electrolytic Phe7iomena in Oxide Coated Filaments? J. A. Becker. 

 A critical survey of the literature shows that the current through the 

 oxides in oxide coated filaments is carried by electrons, negative 

 oxygen ions, and positive barium ions. The proportion of current 

 carried by each depends upon the exact composition and method of 

 preparation of the oxide coating, on the heat treatment and on previous 

 electrolytic effects. Presumably the conductivity is greatly affected 

 by barium and oxygen dispersed through the oxide. New experi- 

 mental results show: 



1. For a particular BaO -f SrO filament, the conductivity C was 

 given by 



1.71 X 10^ ^^lfi°^ + 5.55X10-3 2:52^'. 



^ Phys. Rev., November 15, 1931. 



^ Trans. Electrochem. Soc, \o\. LIX, 1931. 



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