ABSTRACTS OF TECHNICAL ARTICLES 263 



Grossman, A. J., see C. H. Elmendorf. 



Hagstrum, H. D.^ 



Electron Ejection From Ta by He+, He++, and He2+., Phys. Rev., 

 91, pp. 543-551, Aug. 1, 1953 (Monograph 2148). 



Measurements of total yield (7^) and kinetic eneifry distribution are re- 

 ported for electrons ejected from tantalum by the ions, He+, Hc"^ and Hej"^ 

 in the kinetic energy range 10 to 1000 ev. The evidence ])resented indicates 

 that the electrons are released by a collision of the second kind of the ion 

 with the metal surface (potential ejection). One internal secondary electron 

 is produced per incident ion. The probabilit}- of this electron escaping is 

 reduced by the possibility of internal reflection at the image barrier at the 

 metal surface. 7.- for the slowest ions is observed to be 0.14, 0.52, and 0.10 for 

 He"*", He++, and He2+, respectively. The data presented must be considered 

 representati^•e of gas-covered tantalum, since no gas was observed to desorb 

 from the target on heating to 175°K. yi was found not to vaiy with time 

 after cooling the target indicating rapid re-establishment of the equilibrium 

 gas layer on the surface from within the metal. The work function of the 

 covered Ta surface is found to be ca 4.9 ev, some 0.8 ev higher than that 

 of atomicalh' clean Ta. Considerations based on a theory which includes 

 variation of energy levels near the metal surface show resonance neutrahza- 

 tion of He"^ at the covered Ta surface not to be possible. Thus onh- the so- 

 called direct process of potential ejection occurs, with which conclusion the 

 •measured energy limits of ejected electrons are in agreement. 



Hauser, F., see G. R. Crane 



Hawkins, W. L., see B. S. Biggs. 



Heffner, H.^ 



Backward -Wave Tube, Electronics, 26, pp. 135-137, Oct., 1953- 



Electron-stream amplifier utilizing l)ackward-wave mode forms microwave 

 oscillator continuously tvmable o\'er a three-to-one bandwidth b}' a single 

 voltage control. Tubes have been built for frequency centering about 6,000, 

 10,000 and 50,000 mc. 



Henderson, O.^ 



Magnetic Amplifier Controls for Rectifier Protecting Underground 

 Metallic Structures Cathodically, Corrosion, 9, pp. 216-220, July, 

 1953. 



This paper covers the initial attempt on the part of the Ohio Bell Telephone 



1 Bell Telephone Laboratories. 

 5 Ohio Bell Telephone. 



