GB262879A - Improvements in or relating to electron discharge tubes - Google Patents

Abstract

262,879. Siemens - Schuckertwerke Ges., and Berthold, R. G. Sept. 24, 1925. Low - pressure metallic-vapour apparatus; vacuum tubes.- The supply of electrons forming the main discharge is provided by an auxiliary arc or glow discharge, which takes place within a jacket having openings leading to the control chamber, and a high vacuum is main. tained in the control chamber bv the suction action of the auxiliary discharge. As shown in Fig. 1, an auxiliary arc discharge between a mercurv cathode 3 and an anode 4 is confined by a perforated sheath 5, having bent-cut portions arranged so that gas is withdrawn from the space containing the anode 2 to which electrons pass from the arc discharge. The sheath may be used as a control electrode, or separate grids may be provided. The vessel enclosing the anode 4 is cooled externally, and gas may be evacuated from the anode space. As shown in Fig. 3, the auxiliary arc discharge between a mercury cathode 3 and a mercury anode 4 passes through one or more nozzles 6 so that gas is withdrawn from the space containing an anode 2 and a grid 13. The streaming speed of the gas in the arc should be equal to or higher than the molecular speed due to the temperature of the gas in the arc. As shown in Fig. 5, the auxiliary arc passes outside a hollow cylinder 60 and the condensed mercury overflows from the anode 4 to the cathode 3 through the inside of the cylinder, baffles 110 being provided to prevent the passage of the arc inside the cylinder. In the arrangement shown in Fig. 6 the sheath 5 is provided with one or more sets of sloping slots 7 formed by curved guides, and a magnetic field is produced by a winding 16. The sheath is of magnetic material coated with enamel, and the guides are of nonmagnetic material such as porcelain or steatite; or the sheath may consist of powdered iron mixed with glass or powdered quartz. The arrangement is such that electrons are deflected Ly the magnetic field and have a free path through the slots, and gaseous ions strike the guides and condensed mercury flows back to the inside of the sheath. The walls of the sheath may be made hollow for the passage of a cooling medium. A grid 20, consisting of strips mounted edgewise to the path of the electrons, shields electrons passing through the slots from the varying electrostatic fields of the central grid 19 and anode 2. For the same purpose the winding 16 may be energized from the anode 2 or grid 19. A magnetic yoke may be mounted close to the upper or lower end of the sheath or inside the sheath ; or the anode may form the yoke.