1370 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



modes Avith power flows of opposite signs is designated by a and is plotted 

 as the dashed ellipses about the horizontal axis. 



Appendix E 



This appendix comments briefly on various sections and cites refer- 

 ences, which are listed at the end of the appendix. The list of references 

 is not exhaustive, but it should enable the interested reader to follow 

 work back to its source. 



1. Space-Charge Waves 



Space-charge waves of the general sort considered are related to the 

 plasma oscillations of Tonks and Langmuir. Waves in long beams were 

 first discussed by Hahn^ and Ramo.^ The efl"ects of a velocity distribution 

 are discussed by Pierce and by Bohm and Gross. ^ The negative energy 

 of the slow space-charge wave has been reported b}^ Chu^ and by Walker.^ 

 Chu gave the effective "voltage" U and the characteristic impedance K 

 for the waves. 



2. TheKkjstron 



Beck gives an adequate description of and references to klystrons. 



3. The Resistive Wall Amplifier 



The effect has been discussed by Pierce, and a tube using it has been 

 described by Birdsall, Brewer and Haeff.^*^ 



4- The Easitron; Increasing Wave in a Lossless System 



The original easitron was a tube built by L. R. Walker at Bell Tele- 

 phone Laboratories ; it was a 3-cm tube using half -wave wires as resonant 

 elements. It has not been described in the literature. Pierce has discussed 

 the operation of this sort of multi-resonator klystron on page 195 of 

 Traveling Wave Tubes ^ and elsewhere.^ 



5. Coupling of Modes of Propagation 



The operation of traveling-wave tubes was first explained in terms of 

 coupling between an electromagnetic wave and a space-charge waA'e by 

 C. C. Cutler in unpublished work. JMathews has made an analysis in 



