CONCLUSION 669 



theory of conventional traveling-wave tubes. The question of velocity dis- 

 tribution across the beam is particularly important in double-stream ampli- 

 fiers, whose very operation depends on such a distribution, and it is important 

 that the properties of various kinds of distribution be investigated. 



Finally, there is no reason to suspect that the simple tubes described do 

 not have undiscovered relatives of considerable value. Perhaps diligent work 

 will uncover them. 



