11-2] 



THE KLYSTRON 



595 



between the electrons would cause the beam to expand and be lost to the 

 walls of the drift tubes between cavities if additional magnetic focusing 

 were not provided. To constrain and collimate the electron beam, the beam 

 is brought into a strong magnetic field parallel to the beam axis. This 

 magnetic field is continued until the beam has passed through the final 

 cavity, and is then removed. This allows the electron beam to spread 

 because of its own space charge until the power density in the beam is 

 reduced to an acceptably low value, so that the beam can strike the surface 

 of the collector without melting it. A schematic diagram of a high-power 

 multicavity klystron amplifier with magnetic focusing is shown in Fig. 

 11-22. 



Collector - 



Output Cavity 

 Tuning Diaphragm - 



Magnetic Circuit - 



Water Circuit • 



Electron Bea 



-Output Window 



Electron Bunch 

 -Output Iris 



-Anode Pole Piece 



Fig. 11-22 Schematic Diagram of a High-Power, Multicavity Klystron Amplifier, 

 with Magnetic Focusing. 



