GB633831A - Improvements in electron-discharge apparatus utilising electron-velocity modulation - Google Patents

Abstract

633,831. Velocity-modulated tubes. SPERRY GYROSCOPE CO., Inc. Aug. 16, 1946, No. 24377. Convention date, Aug. 30, 1945. [Class 39 (i)] A velocity-modulation electron discharge device has a field-free drift space with a length such that the transit time is less than one cycle of the fundamental frequency, and a circuit tuned to a harmonic of the fundamental frequency and excited by the density modulated electron stream, the circuit energy being extracted at the harmonic frequency. The maximum amplitude of the input voltage is greater than the beam voltage and a proportion of the electrons in the stream are reversed in direction. As shown in Fig. 1, electrons from cathode 11 are accelerated by grid 12 and control electrode 15 and flow successively through buncher grids 13, 14 along the drift tube 16 and through the output grids 17, 18 to electrode 19 which has cooling fins. A cavity resonator 21 surrounds the tubular member 25 containing the electron streams and an extension 26 to the member 25 provides a fixed capacity loading reducing the necessary size of resonator 21, another tubular member 27 providing an additional lumped capacitance. The input terminal comprises a loop 31 and a coaxial line section 29, 30. The output resonator 32 is connected between grids 17, 18 and the output terminal 37 is also a loop and coaxial line. Resonator 32 is designed and adjusted to be resonant at the desired harmonic frequency. The theoretical optimum value for the length of the drift tube 16 is stated to be 2 - or 0.64 the distance travelled by the electron # in one cycle of the fundamental frequency.