ELECTRON BEAM IN THE COLD-CATHODE MAGNETRON

The cold-cathode magnetron with various cathode materials is examined. The kinetic energy of electrons in the direction of the magnetic field is found. The anode current and cathode back bombardment are formulated on the basis of statistical mechanics. Noise and bunching are studied. It is shown here for the first time that the space charge starts to bunch most easily when the length of a useful bunch is equal to the distance between cathode and anode in both smooth-anode magnetrons and in magnetrons with a slow-wave RF anode structure. Several RF anode configurations are discussed, and the results are given. It is found why the easiest starting configuration has the wavelength of the slow-wave structure equal to double the spacing between cathode and anode, and why the minimum starting value of magnetic field makes the cyclotron frequency equal to double the frequency of the slow-wave structure, when a specific energy of back bombardment is demanded by the cold-cathode secondary emitter.