GB860758A - Improvements in or relating to x-ray tubes and circuit arrangements - Google Patents

Abstract

860,758. X-ray tubes. RILEY, D. P. April 21, 1958 [April 26, 1957(2)], Nos. 13466/57 and 13467/57. Class 39(1). [Also in Group XXXV] In an X-ray tube comprising three or more pairs of electrodes, each pair consisting of a cathode and an anode, the electrodes are so arranged and adapted for connection to a poly-phase electric supply that each cathode can emit electrons to two anodes and each anode can receive electrons from two cathodes. As shown in Fig. 3, the electrodes may be coplanar, or arranged on a conical surface, each of the anodes 2, 4, 6 being provided with two tungsten targets 26, 27 and having a tube 21 arranged therein for connection to a supply of cooling fluid. Each of the cathodes 3, 5, 7 has a helical filament 14 arranged behind elongated slits 17, 18 in the shield 8. In an alternative arrangement the cathodes and anodes are arranged at opposite ends of the tube with their axes parallel. Both the cathodes and anodes are equi-angularly disposed about the tube axis, cathodes and anodes facing each other and being staggered in angular disposition. The cathodes are similar to those shown in Fig. 3 but each of the anodes has a flat end face in which a single target is provided. In operation of a tube having three pairs of electrodes each anode is connected to the cathode from which it does not receive electrons and these pairs of electrodes are connected to the apices of delta-connected high-tension secondary windings of a three-phase step-up transformer so that each anode emits X-rays continuously for two-thirds the period of each cycle and the total emission of X-rays from the tube is continuous and of nearly uniform intensity. In a further embodiment each pair of electrodes forms a unitary structure comprising a tungsten anode 30, Fig. 9, and a filamentary cathode 34 supported by anode skirt 32 and formed as a zig-zag grid in front of the target face 31, three such structures having coplanar axes radiating from a central point at angles of 120 degrees to one another. The cathode may be connected directly to the anode or may be insulated therefrom as shown. In the latter case the cathode may be connected to the anode by way of an adjustable resistor so that the anode acts as a repelling plate for electrons emitted by the cathode and the cathode acts as a control grid when the structure is receiving electrons from a second electrode pair.