376 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



GLOSSARY OF SYMBOLS 



Ai , 2 anode designations 



B, C anode potentials 



Ci , 2 functions used in evaluating cr+' 



dA increment of area 



dl, dz increments of length 



e . electronic charge, base of natural logarithms 



En electric field normal to electron path 



F modified focal length of the anode lens 



Fd focal length of the anode lens as given by Davisson^ 



Fn force acting normal to an electronic path 



Fr , a fraction of the total current which would flow through 



a circle of radius r, a 



/, Id total beam current 



It beam current within a radius, r, of the center 



J current density 



k Boltzman's constant 



K - a quantity proportional to gun perveance 



m electronic mass 



P gun perveance 



P{r) probability that a thermal electron has a radial posi- 



tion between r and r -\- dr 



r radial distance from beam axis 



Va , c anode, cathode radii 



r^ distance from beam axis to path of an electron emitted 



with zero velocity at the edge of the cathode 



rgs radius of circle through which 95% of the beam cur- 



rent would pass 



f distance from center of curvature of cathode; hence, 



fc is the cathode radius of curvature and (fc — fa) 

 is the distance from cathode to anode 



re+' slope of edge nonthermal electron path on drift side of 



enode lens 



Te-' slope of edge nonthermal electron path on gun side of 



anode lens 



R a dummy integration variable 



t time 



T cathode temperature in degrees K 



u longitudinal electron velocity 



Vc , X , y transverse electron velocities 



V, Va , f , X beam voltages with cathode taken as ground 



