GB443844A - Arrangements for producing thin bundles of electron rays from large surface cathodes - Google Patents

Abstract

443,844. Cathode-ray tubes. LORENZ AKT.-GES., C., 1, Lorenzweg, Tempelhof, and ARDENNE, M. VON, 19 Jungfernstieg, Lichterfelde-Ost, both in Berlin. Sept. 7, 1934, No. 25803. Convention date, Sept. 8, 1933. [Class 39 (i)] Electrons from a large surface cathode are formed into a convergent beam and then into a parallel bundle of rays of small crosssection and the intensity of the rays is controlled by an intermediate electrode arranged in the path of the rays so that the straight lines of the electric field are not disturbed. A protective ring 1 surrounds the emissive cathode surface 2 to keep the lines of force perpendicular to the cathode at its edge. The cathode and ring may be planar with the electrons drawn off in parallel lines before being converged or may be curved convexly or, as shown, concavely to produce directly a convergent beam, the intensity control electrode 3 being curved. The convergent beam, before passing through the deflecting system, is converted into a parallel beam by a dispersing electron lens immediately in front of the focus 5 or by a converging lens after the focus or by shutters which form an acceleration field of parallel lines and the first of which is at or near the focus. The cross-section of the ray is determined by the shape of the cathode or shutters. Magnetic or electrostatic lenses may be used and may be cylindrical and formed by wire networks. Screening electrodes at potentials corresponding to the electron velocity at the electrodes may be used, for example, to screen the electron lenses from the deflecting system. The tube may contain gas fillings below 10<-3> mm. pressure to prevent straying of the rays in the parallel beam, hydrogen or argon or combined fillings at 10<-5> mm. being specified.