. The Bell System technical journal . Fig. 4.—Electron paths in a cylindrical DC magnetron at several magnetic fields aboveand below the cut-off value, Be. The electrons are assumed to be emitted from the cathodewith zero initial velocity. curve, are shown in Fig. 5. For the case of parallel plane electrodes, thecut-off relation between the critical anode potential, Fc, and magnetic , and the electrode separation, d, for the parallel plane case, is obtainedby equating the electrode separation to the diameter of the rolling , d = \d)BV 2 -t -f 1-, from which F. = eBtd2m MAGNE
. The Bell System technical journal . Fig. 4.—Electron paths in a cylindrical DC magnetron at several magnetic fields aboveand below the cut-off value, Be. The electrons are assumed to be emitted from the cathodewith zero initial velocity. curve, are shown in Fig. 5. For the case of parallel plane electrodes, thecut-off relation between the critical anode potential, Fc, and magnetic , and the electrode separation, d, for the parallel plane case, is obtainedby equating the electrode separation to the diameter of the rolling , d = \d)BV 2 -t -f 1-, from which F. = eBtd2m MAGNETRON AS GENERATOR 01 CENTIMETER WAVES 177 For the cylindrical case, the relation may be shown to be (8) -■■•-ff--(;;)■]■ in terms of cathode and anode radii, r< and fa- 2. Types of Magnetron Oscillators Definitions: The DC magnetron may be converted into an oscillator,suitable for the generation of centimeter waves, by introducing RF fields intothe anode-cathode region. This may be done by applying between anode. MAGNETIC FIELD, B Fig. 5.—Variation of current passed by a cylindrical DC magnetron at constant voltage,plotted as a function of magnetic field. The orbits of electrons occurring at four differentmagnetic fields are shown above the corresponding regions of the current characteristic. and cathode RF voltage from a resonant circuit, in which case the electronsinteract with the superposed radial RF field. Or, it may be done by split-ting the magnetron anode into two or more segments between which theRF voltage is applied. Then the electrons interact with the fringing RFfields existing between the segments. The problem of understanding theelectronics of the multicavity magnetron oscillator is that of understandinghow an electron, subject to the constraints placed upon its motion by theDC axial magnetic and DC radial electric fields, can move so as to interactfavorably with the RF field; how an electron interacting unfavorably isrejected; and why, on th
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