GB231467A - Improvements in or relating to x-ray tubes - Google Patents

Abstract

231,467. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. March 27, 1924, [Convention date]. R÷ntgen-ray tubes. - A tube having an incandescent cathode within a metal casing, forming a part of the envelope and insulated from the anti-cathode, is provided with a " getter " consisting of an electropositive metal such as magnesium; caesium is not suitable. A piece of magnesium may be electrically welded to the inside of the metal casing 2, or placed in a shallow depression therein; after the tube is sealed off from the pump, the metal casing is heated to volatilize the magnesium, which is deposited over the inside of the casing. Alternatively, a second filament 14 is coated with the " getter," and is heated by current after exhaustion. A very high vacuum may be produced, or a little hydrogen or helium may be present. The seal 11 at the upper end of the metal casing is shielded by a sleeve 12 integral with the casing. A metal cover 3 for the casing has a central aperture for the passage of cathode rays and of X-rays from the anti-cathode 4. Sealed to the bottom of the casing 2 is a glass dome 5 through which pass leading-in wires 7, 15 for one end each of the main and auxiliary filaments 1, 14, the return connections being made through the casing. An annular metal plate 6 is fitted in the lower end of the casing.