GB691900A - Electron discharge devices - Google Patents

Abstract

691,900. Velocity-modulated tubes. KOMPFNER, R., and BUCKINGHAM, J. Nov. 13, 1950 [May 19; 1949], No. 13374/49. Class 39(i) In an amplifier comprising an evacuated waveguide structure 2 traversed by an electron beam directed transversly or inclined to the direction of wave propagation therein, interaction regions separated by drift spaces are formed by localized concentrations of the electric field in such a way that the electrons experience substantially the same phase conditions at all the local concentrations, the electron beam thereby becoming bunched and thereafter delivering energy continuously to the wave at each interaction region. The structure 2 consists of an array of parallel metal or dielectric strips, Fig. 2, the spacing apart r of which is less than half the spacing s in the direction of electron travel. The thickness b of the strips is as small as practicable to allow maximum beam current to pass between them. The electrons from the cathode 1 are focused, as by a magnetic field H. Input and output waveguides 5, 6 are coupled to the amplifier by horns 7, 10, and artificial or natural dielectric lenses 8, 9, the output lens and horn being tilted if necessary, to allow for tilting of the wave fronts caused by the interaction with the electron stream. The output may be taken from a second waveguide structure within the envelope but spaced from the first structure 2 by a drift space, the performance of this tube being analogous to that of a klystron. The structure 2 may be made resonant by enclosing it in a metal casing, Fig. 3 (not shown), such that the walls of the casing are n #/2 apart and are provided with narrow slots for coupling with the unloaded space outside. Such a device acts as a self-oscillator. The electrode 3 serves as a collector, alternatively it has a negative bias and reflects the electron beam back through the structure or structures.