GB208108A - Improvements in or relating to x-ray tubes - Google Patents

Abstract

208,108. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. Dec. 6, 1922, [Convention date]. R÷ntgen-ray tubes. - An incandescent cathode is mounted in a container consisting entirely or mainly of metal from which the anode is insulated, and the electrodes and container are so shaped that the electron stream strikes a small area only of the anode. As shown in Fig. 2, the metal container 6 is constricted to form a small aperture 7 around the anode 8, which is mounted on a re-entrant glass tube 5 sealed to the container. The cathode consists of a circular tungsten filament 9 mounted -on legs 16 of molybdenum secured to a ring 15 of glass or porcelain. A glass window 13 is sealed to the container and is protected from the electron discharge by a thin plate 14, grid, or gauze of aluminium or silver transparent to Rontgen rays. The filament leads are sealed through a glass tube 12. The container is maintained at a negative potential with respect to the filament so as to prevent the passage of electrons thereto; for this purpose one of the filament leads may be connected with the container either directly or through a resistance. By adjusting the potential of the container the area of the anode struck by the electron stream may be slightly varied. Or the potential of the container mav be slightly positive. In a modification, the anode is pointed and extends through an aperture in a cover. In the arrangement shown in Fig. 4, the anode 25 is mounted behind an aperture 33 in a slanting cover 24, and a window 26 is sealed into the side of the container 23. The cathode 28 is mounted on a glass cap 29 and is connected through resistances 31, 32 with a battery 30, the negative terminal of which is connected with the container. In another arrangement the anode consists of a small sphere and the container is of spherical shape. The container may be, of copper or iron with a sealing ring of platinum or of chrbme-iron having the same coefficient of expansion as glass; or the container may be made entirely of chrome-iron.