CATHODE PROBLEM IN PULSED MAGNETRONS

There are two different expressions for anode current of pulsed magnetrons. The one. comprising electric and magnetic parameters as well as tube geometries, describes how the electrons are picked up from the rotating electron stream near anode space; the other, stating the relation between thermal emission, coefficient of back bombardment and coefficient of secondary emission, is a general description of supplying electrons to the rotating stream by the ca-thode without concern to a particular tube. Each of the above expressions has its own physical significance while they are closely connected to each other through the rotaing eectron stream. The integration of these expressions with the electron motions in the interaction space leads to better understanding of the mechanism of magnetrons. For stable operation of the magnetron, the preoscillation voltage should be lower than the threshold voltage, while the mode of this space charge oscillation should be the same as the mode oscillation on the resonating cavities. After starting of the resonance, that the thermal emission approximately equals the back bombarding current and the secondary emission approximately equals the anode current respectively exhibits condition of good performance.