2 BELL SYSTEM TECHNICAL JOURNAL 



excellent review of this literature and the history of electron-optics 

 are given in a symposium * of papers published in 1936, and the 

 various practical applications of electron lenses are well described in 

 the books on that subject.^ 



E, = 



___:::::rE2 



EQUIVALENT 

 LENSES 



APERTURED PLATE 



+ + 



TUBES SAME SIZE 



EQUIVALENT 

 LENSES 



CONCENTRIC TUBES 

 Fig. 1 — Lines of force in typical electron lenses. 



TUBES DIFFERENT SIZES 



^Zeit.f. techn. Physik, 17, 584-645, 1936. 



■> E. Briiche and O. Scherzer, Geometrische Eledronenoptik (Springer, 1934). 

 J. T. MacGregor- Morris and J. A. Henley, "Cathode Ray Oscillography " (Mono- 

 graphs on Electrical Engineering), 1936. Maloff and Epstein, "Electron Optics in 

 Television" (McGraw-Hill, 1938). 



