GB773834A - Improvements in or relating to electron wavetubes - Google Patents

Abstract

773,834. Space charge wave tubes. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. April 27, 1955 [April 27, 1954], No. 12183/55. Class 39(1). A high frequency space charge wave oscillation generator comprises two electron beams projected in opposite directions and separated by a " geometrically periodical structure " such as a grid, or a ladder delay line, which is designed so as to be incapable of propagating waves in the operating frequency band of the tube, and a delay line section or other periodical coupling means disposed near one or both ends of the geometrically periodical structure and connected to a respective output connection or connections and the beam velocity can be varied for electronic tuning. It is stated that due to noise components carried by the beams and the close proximity of the beams to one another, interaction takes place between the beams through the geometrical periodical structure which become density modulated, the distance between the electron bunches and consequently the output frequency depend on the pitch of the geometrically periodical structure and its voltage, variation of its voltage giving electronic tuning. In one form, Fig. 1, two concentric beams 1, 2 travelling in opposite.directions are separated by a grid structure 3 (the geometrically periodical structure) comprising wire rings 18 carried by metal rods 17. Short helical delay line sections 6, 7 give two outputs to feeders 14, 15, their free ends being terminated by colloidal graphite loss coatings 4, 5. The two output lines are joined by a connection 30 within the tube. Structure 3 is given an adjustable positive potential by potentiometer 13 to give the beams the desired velocities which are equal to one another but oppositely directed. The oscillation frequency is said to be the beam velocity divided by the distance between the bunches of the density modulated beams. It is stated that more than two beams of the same or different velocities can be used. The geometrical periodical structure 3 can in general be a grid with square circular or polygonal meshes, or a ladder delay line 35, Fig. 4, separating two parallel oppositely travelling beams 31, 32. The device operates with crossed electric and magnetic fields and ladder line 35 is positive with respect to electrodes 36, 37 setting up the transverse electrostatic field, the potentials of 36, 37 being adjustable by potentiometers 52, 53. Flat helical delay lines 48, 49 extract two outputs, the free ends of the delay lines being coated with loss material as before. The velocities of the beams may be varied by varying the potentials of 36 or 37 by potentiometers 52, 53 or by varying the magnetic field. The tube of Fig. 4 can be bent into circular form.