GB547979A - Magnetic control vacuum tubes - Google Patents

Abstract

547,979. Electron discharge valves. STANDARD TELEPHONES & CABLES, Ltd. March 14, 1941, No. 3493. Convention date, March 20, 1940. [Class 39 (i)] A thermionic valve comprising a cathode, anode, and control electrode, together with means for producing a magnetic field in the space between the cathode and anode parallel to the direction of electron flow so as to direct the electrons past the control electrodes, comprises also a part or parts of magnetic material forming a complete circuit for the magnetic field except for a gap in which the electrode assembly is located. In the form shown in Figs. 1 and 2, a cylindrical anode 10 of magnetic material forms part of the envelope of the tube, the envelope being completed by a glass cap 11 sealed to the anode and a glass ring 12 sealed to it and to an insulating support 15 for a central rod 13, also of magnetic material, which carries radially-extending control electrodes 16. These electrodes may be plates or of wire mesh, and between them are arranged cathode filaments 17 extending between a ring member 18 and terminals 19. A radial magnetic field extending between the electrodes 10, 13 is produced by a winding on a core 14 in line with the latter, causing the electrons to travel in a helix the diameter of which may be controlled by the field so that they do not reach the control electrodes 12. In the form shown in Fig. 3 the control electrode plates 36 are perpendicular to the anode plates 30, and the cathode filaments 37 are arranged between them. A field parallel to the plates 36 is produced by a magnet 32 external to the tube envelope. In a further form a cathode and anode are arranged one at each end of a cylindrical control electrode through which the electron stream passes, an external winding in a shell of magnetic material producing a magnetic field in the direction of the axis of the control electrode.