GB803709A - Improvements relating to velocity-modulated electron discharge devices - Google Patents

Abstract

803,709. Veolicity-modulated tubes. GENERAL ELECTRIC CO. Dec. 30, 1955 [Jan. 25, 1955], No. 37450/55. Class 39(1). In a velocity-modulation device of the klyston type having a triode input section including a cathode control electrode and second electrode spaced apart in that order in the direction of the electron beam, capacitive coupling is provided between the control electrode and cathode so that they operate at substantially the same r.f. potential but are maintained d.c. insulated from each other and the control electrode is so spaced relative to the cathode that the leakage from any electromagnetic field established between the control electrode and second electrode causes space charge control of the cathode emission to augment the velocity modulation of the electron beam. As shown in Fig. 2, the tube comprises an input section 20 a drift tube 21 and an output section 22. The beam is generated by a cathode 33 comprising an emitting surface 34 and a heater 35 and passes through a control grid 37 spaced from the emitter 34 by an insulating annular disc 40 of zero impedance to radio frequency, the control grid 37 being in D.C. contact with the inner member 25 of the input resonator. The input resonator comprising mixer and outer members 25, 24 is tuned by plungers 27 and fed by a capacity coupled coaxial line 32. The output resonator, 51, 52 is similarly tuned by plungers 53 and feeds a coaxial line 62. The drift tube 21 is formed by a conductive non-ferromagnetic cylinder 41 attached at either end to the outer members 24, 51 of the resonators, the beam passing via gaps 48, 58 into and from the drift tube through grids 44, 45 respectively. In order to alter the Q factor without altering electrode spacing or potential levels lossy material 70, Fig. 4, may be provided at the grid end of the inner member 25 of the input resonator. The lossy material may be quartz coated with stannous chloride or may be a ferite and may be adjustable axially. In a modification the inner member 25 of the input resonator contacts the cathode 33 instead of the control grid 37. For optimum efficiency the A.C. velocity component of the stream should lag the A.C. current component by 90 degrees and the average transit angle from cathode to drift space entrance should be 2# radiam.