ELECTRON GUN 



337 



Second anode 



Control grid First anode 



Cathode 



Approx. optical analogy 



Fig. VIII-16. An electron lens-system due to Zworykin. Sections of the elec- 

 tric equipotential surfaces are shown in solid lines, electron beam in broken lines. 

 Potential of second anode about twice as great as first anode. Approximate optical 

 analogy just below. (By courtesy of V. K. Zworykin [1933 and 1934].) 



+50 +1000 +1000 



100 to 1500 volts 4 



Fig. VIII-17. A diagrammatic representation of electron guns having same 

 physical dimensions but charged as in (a) to give a divergent beam and in (b) to give 

 a convergent beam of electrons, (c) Diagrammatic section of an assembled electron 

 gun. Note cross-over at aperture and subsequent convergence of beam. (By cour- 

 tesy of R. H. George [1929].) 



