MAGNETRON AS GENERATOR OF CENTIMETER WAVES 



193 



hand, will be found opposite the negatively charged anode segment beyond 

 the gap when the RF field is maximum, and for it the net effect of the radial 

 component is to reduce the mean velocity of the electron, bringing it also 

 more nearly into the proper phase. 



In discussing the mechanism of phase focusing from the traveling wave 

 point of view, the field lines of Fig. 14 may be considered to be those of the 

 traveling wave component with which the electrons are interacting. Then 

 the whole field pattern indicated moves to the right as shown by the arrow 

 above the plane of maximum retarding tangential field at M. An electron 



Fig. 14. — A plot of lines of electric force on an electron (drawn for the plane case) for the 

 fundamental of the x mode. It is shown for the purpose of explaining the phase focusing 

 property of the radial field component. The plane of ma.ximum opposing force on the 

 electron intersects that of the figure along the line M . The arrow shown above the line M 

 indicates the direction of electron motion. The force on the electron due to the DC 

 electric field is directed from cathode to anode. The force lines shown may be considered 

 to be those of the total fundamental field component at the instant the field is maximum. 

 Then an electron at the point P will cross the center of the anode gap after the instant of 

 maximum retarding force. Or the lines shown may be considered to be those of the travel- 

 ing component of the fundamental moving in the same direction as the electrons. In this 

 case an electron at the point P is lagging behind the maximum of the retarding tangential 

 field. 



which falls behind the position M to the point P, for example, finds itself in 

 a stronger net radial electric field which increases its mean translational 

 velocity tending to bring it back to the position M. The reverse holds for 

 an electron which runs ahead of the plane M. 



Z.S Space Charge Configuration: The over-all picture of the electronic 

 mechanism in the Type III magnetron oscillator thus presents a spoke- 

 shaped space charge cloud of electrons wheeling around the cathode in 

 synchronism with the anode potential wave, each spoke in a region of maxi- 

 mum retarding field. This picture of what is happening has been very 

 handsomely confirmed by actual orbital calculations taking account of 



