MAGNETRON AS GENERATOR OF CENTIMETER WAVES 



191 



mate orbit is shown in Fig. 13. It is instructive to compare the orbits of the 

 two categories of electrons in the traveling wave magnetron oscillator with 

 the orbits of corresponding electrons in the cyclotron frequency type of 

 magnetron oscillator (Figs. 7 and 8). In each case, it is the fact that "favor- 

 able" electrons may interact for a considerably longer time than "unfa- 



Fig. 12. — An approximate orbit of an electron which is losing energy to the RF field in 

 a traveling wave or Type III magnetron oscillator, shown for the plane case. Here the 

 energy loss is potential energy of the electron in the DC field. Compare this with the 

 orbit in Fig. 8 where the energy loss is rotational energy of the electron. The DC electric 

 force on the electron is directed from cathode to anode. 



Fig. 13. — An approximate orbit of an electron which gains energy from the RF field in 

 a traveling wave or Type III magnetron oscillator, shown for the plane case. The orbit 

 is extended as a dashed line as though the cathode were not there. The energy gained is 

 potential energy of the electron in the DC field. Compare this with the orbit in Fig. 7 

 where the energy increase is in the rotational energy of the electron. The DC electric 

 force on the electron is directed from cathode to anode. 



vorable" electrons which makes possible a net energy transfer between the 

 DC and RF fields. 



One may now compare the traveling wave picture of the electronic mecha- 

 nism with that presented earlier in which the motion of electrons past the 

 gaps in the anode structure is considered. An electron moving so that 



— ~ I ^ I + 1^7 cycles of the RF oscillation elapses between its crossing of 



two successive anode gaps, is thus moving around the interaction space in 

 synchronism with a traveling component of the kth harmonic of the inter- 



