BEAM FORMATION WITH ELECTRON GUNS 



417 



CO 



20 

 18 

 16 

 14 

 12 



t- 8 



2 

 



I 



50 

 45 

 40 

 35 



if) 30 



Z 25 



l? 20 



15 



10 



40 



80 120 160 200 240 



Z, DISTANCE FROM IDEAL ANODE IN MILS 



280 



320 



100 200 300 400 500 600 



Z, DISTANCE FROM IDEAL ANODE IN MILS 



700 



800 



Fig. 15 — Beam profiles (using an anode lens correction of r = 1.1 and the gun 

 parameters indicated) as obtained (A) from experiment, (B) bj^ the methods of this 

 paper, (C) Hines-Cutler method, (D) by use of the universal beam spread curve. 



universal l^eam spread curve'" (i.e., under the assumption of laminar 

 flow and gradual variations of beam radius with distance) . Note that in 

 each case a value of 1.1 has been used for the correction factor, r, repre- 

 senting the excess divergence of the anode lens. The agreement in 

 (/'95)min as obtaiucd from Curves A and B is remarkably good, but the 

 axial position of (r95)min in Curve A definitely lies beyond the correspond- 



