GB683475A - Improvements in or relating to electric discharge tubes for accelerating particles - Google Patents

Abstract

683,475. Discharge apparatus. RESEARCH CORPORATION. Oct. 11, 1949 [March 16, 1949], No. 26063/49. Class 39(i) In an evacuated high-voltage acceleration tube the wall of the tube is wholly composed of a multiplicity of thin metallic ring-like electrode members and alternating ring-like insulating members bonded together in contacting face to face relation between the respective end cathode and anode assemblies, and for the purpose of reducing the tendency to produce secondary particles (such as electrons, positive ions or photons) and at the same time increasing the voltage gradient which can be applied along the tube, the metallic members are each thin and each has an axial opening, the size or transverse positions of the openings varying along the length of the tube beginning immediately following the cathode assembly but without necessary changes in the diameter of the insulating members or of the openings therethrough. Fig. 1 shows an X-ray tube for use with voltages of the order of 2 million volts; the cathode assembly 3 is bolted to the tube with an intervening gasket and the cathode itself may be a tungsten filament 8. The electrodes 11 have apertures which increase progressively in size to the anode assembly 2 which may include a gold anode target 9. In a modification, Fig. 2 (not shown), the electrode nearest the cathode has a wide aperture and the apertures of the electrodes decrease in size to a minimum about a quarter of the way along the tube and thereafter progressively increase to a maximum at the anode end of the tube. In further modifications, Figs. 3 and 4 (not shown), the apertures increase stepwise instead of continuously, that is to say several adjacent electrodes have the same aperture and the next group of electrodes has a slightly larger aperture. In a further modification, Fig. 6 (not shown), the apertures are all of the same diameter but are placed eccentrically, the eccentricity being progressively advanced circumferentially. In a positive ion tube where hydrogen or deuterium may escape into the tube from the ion source and pumping speed is important, the electrodes with small apertures may be provided with further apertures which take no part in the discharge but assist in maintaining pumping speed. Fig. 5 (not shown). Specification 703,471 is referred to. The Specification as open to inspection under Sect. 91, comprises also the use of electrodes of which the apertures progressively decrease in size from the cathode to the anode, a construction which may be particularly useful in positive ion tubes. This subject-matter does not appear in the Specification as accepted.