Gl^IDKD-WAVK l'U( )1'A(; ATIO.N TllUOlHiU CY UOMAGNETIC MEDIA 581 



larizcd waves in circularly cylindrical ^iiide filled with ferrite or plasma 

 is then considered. The characteristic equation connecting frequency 

 and propagation constant is first derived. For the purpose of obtaining 

 results which can be compared with experiment, a specific molecular 

 model is chosen for the ferrite. In this way the ferrite itself is specified by 

 a single parameter, its saturation magnetization, and its state by an- 

 other, namely the applied field. The object of the calculation, then, is 

 to find, for a given ferrite and a gi\''en guide radius, the mode spectrum 

 of the Avave guide and the A'ariation of propagation constant with mag- 

 netic field. This is done by a semi-graphical method supplemented by 

 exact analj'tic formulae in the neighborhood of certain critical points, 

 series expansions in certain regions and some numerical computations 

 in others. A sketch of a similar procedure applicable to the plasma is 

 given. 



It should be pointed out that the filled cylindrical waveguide is not a 

 topic of the highest importance from the technical standpoint. It is for 

 this reason that no effort is made here to obtain a comprehensive body 

 of exact numerical information about the modes. One wishes, on the 

 other hand, to exploit the simplifying features of the problem (as con- 

 trasted with the more useful case of a cylinder of ferrite not filling the 

 guide) so that the discussion may be exhaustive, in the sense that the 

 complete mode spectrum is exhibited. 



In Part II we deal with cases of transverse magnetization. By that 

 term we mean the following: the microwave fields propagate in a direc- 

 tion normal to the dc magnetization and they do not vary along the 

 magnetization direction. They may then be separated into two inde- 

 pendent sets of field components, of which only one explicitly depends 

 on the dc magnetizing field. For these two fields wave impedances are 

 defined which can be used for matching purposes. A few simple examples 

 are then given. One special case, that of the ''non-reciprocal helix" utiliz- 

 ing ferrite, is of importance in traveling-wave tube work and is discussed 

 at length.'^ The slow-wave propagation along both a cylindrical and a 

 ''plane" heUx are treated; magnetic loss is analyzed in some detail for 

 the plane case, and general rules are given for its approximate deter- 

 mination in the cjdindrical case. 



In Part III pertur})ation theory and some miscellaneous topics are 

 taken up. Suital)le perturbation methods are developed for cases in 

 which the wave guide fields are drastically modified over small volumes 

 (as occiu's if thin pencils or thin discs are inserted) and also for situations 

 in which the local properties of the medium are but slightly disturbed 

 over finite volumes. Among the miscellaneous topics dicusssed is the 



