Patent GB-703471-A (GB)
Abstract: 703,471. Electric discharge tubes. RESEARCH CORPORATION. Dec. 16, 1947 [Dec. 20, 1946], No. 33114/47. Class 39(1) A high voltage, sealed-off or continuously pumped, high vacuum discharge tube, particularly an X-ray tube, the wall of which is at least partially assembled of flat ring-like metal discs with distance pieces of an insulating material there between, connected vacuum-tight with the metal discs, is characterized in that the metal discs are connected with the insulating distance pieces by means of a very thin layer or film of a synthetic resin of the thermo-plastic or thermo-hardening type, e.g. vinyl acetate. The coefficients of expansion of the metal discs and insulating distance pieces may differ. The cathode and anode members at the ends of the tube can be likewise bonded to the assembled tubes, Fig. 3, illustrates the cathode end of the tube, 1 being glass or porcelain distance pieces, 2 the metal rings, 5 the films of bonding material and C the cathode assembly including a tungsten filament emitter 3 and charcoal and getter material for the absorption of residual gases. Fig. 4 illustrates the anode end A of the tube, the electron beam being focused on a target 4, preferably of gold, when the tube is used for generating X-rays. The bonding films 5 can be of Vinylseal T-24-9, a modified vinyl acetate, the material known under the Registered Trade Mark " Glyptal ", nylon, Formvar, silicone resins or a variety of plastic adhesives, The films may be as thin as 0.0005 inches. An accelerator tube may have an over-all length of about four feet and an outside diameter of about three inches, the diameter of the opening of each metal ring 2 being about one inch. The total length of the portion of the tube that is composed of the glass rings 1 and the metal rings 2 is about twenty-four inches. A six-section tube is also referred to employing a 96 per cent silica glass of the material known under the Registered Trade Mark " Vycor " in annular rings between flat stainless-steel diaphragms, a voltage of 480,000 being insulated across a total tube length of 2“ inches. An accelerator tube comprising an insulating column of sixty alternate silica glass sections and metal discs insulating a voltage in excess of 2,000,000 is also referred to. The accelerator tube can be used for generating an accurately focused beam of electrons or ions, means for providing a source of high voltage being an electrostatic generator such as is . disclosed in Specification 539,645, [Group XXXV]. The wall of the tube comprises metallic electrode rings joined to glass or porcelain insulation sections by the films of synthetic resin. The electrode rings are connected to corresponding electrodes of the high voltage generator in such a way that the potential gradient down the tube is uniform and equal steps in the voltage between successive electrodes are provided. With the use of a magnetic lens in the tube fine focusing is obtained. The focused spot upon the target may be less than 0.01 of an inch in diameter if a relatively weak magnetic lens is used. Ultra high frequency transmitter and receiver tubes are also referred to. Fig. 5 shows a three element tube constructed in accordance with the invention. The tubes can be made by the method described in Specification 703,485. Specifications 376,761; 458,702 and 559,057 are referred to. The Specification as open to inspection under Sect. 91 comprises also the method of making the tube joining the subject-matter of Specification 703,485, using the bonding material for forming metal to metal particularly the cathode and anode assembles to the rest of the tube, the use of shellac as a bonding material, and the use of charcoal, silica-gel or the material known under the Registered Trade Mark "Alundum " together with barium, calcium or zirconium for removing vapours and gases after the tube has been sealed off, the charcoal being interposed between the barium &c. and the body of the tube. This subject-matter does not appear in the Specification as accepted.