The Bell System Technical Journal 



Vol. XXIX January, 1950 JSfo. 1 



Copyright, 1950, American Telephone and Telegraph Company 



Traveling-Wave Tubes 



By J. R. PIERCE 



Copyright, 1950, D. Van Nostrand Company, Inc. 



The following material on traveling-wave tubes is taken from a book which 

 will be published by Van Nostrand in September, 1950. Substantially the 

 entire contents of the book will be published in this and the three succeeding 

 issues of the Bell System Technical Journal. 



This material will cover in detail the theory of traveling-wave amplifiers. In 

 addition, brief discussions of magnetron amplifiers and double-stream amplifiers 

 are included. E.xperimental material is drawn on in a general way only, as in- 

 dicating the range of validity of the theoretical treatments. 



The material deals only with the high-frequency electronic aiul circuit be- 

 havior of tubes. Such matters as matching into circuits are not considered; 

 neither are problems of beam formation and electron focusing, which have been 

 dealt with elsewhere.^ 



The material opens with the presentation of a simplified theory of the travel- 

 ing-wave tube. A discussion of circuits follows, including helix calculations, a 

 treatment of filter-type circuits, some general circuit considerations ivhich show 

 that gain will be highest for low group velocities and low stored energies, and a 

 justification of a simple transmission line treatment of circuits by means of an 

 expansion in terms of the normal modes of propagation of a circuit. Then a de- 

 tailed analysis of overall electronic and circuit behavior is made, including a 

 discussion of various electronic and circuit waves, the fitting of boundary con- 

 ditions to obtain overall gain, noise figure calculations, transverse motions of 

 electrons a) id field solutions appropriate to broad electron streams. Short treat- 

 ments of the magnetron amplifier and the double-stream amplifier follow. 



^ For instance, "Theory and Design of Electron Beams," J. K. Pierce, Van Nostrand, 

 1949. 



