Patent GB-674924-A (GB)
Title: Improvements in electron storage devices with grid control action
IPC: H01J31/60
Filed: 1948-02-27
Abstract: 674,924. Cathode-ray tubes. RADIO CORPORATION OF AMERICA. Feb. 27, 1948 [Jan. 15, 1947], No. 6131/48. Class 39 (i). An electron discharge device for memory storage comprises a source of electrons, first and second target electrodes, a collector electrode adjacent the first target electrode, and a grid structure for selectively directing electrons, and a grid structure for selectively directing electrons towards one or more elemental areas of the target, wherein the elemental areas are charged to either one of two potentials and whereby the flow of electrons towards the second target is dependent upon the potentials of the elemental areas of the first target. In one form, Fig. 1, the electrons from cathode 21 are accelerated by spiral grid 23, focused by plates 25, 27, and then pass normally through second accelerating apertured plate electrode 29. They then pass through horizontal control grid wires 31, shield electrode 35, vertical control grid wires 37, collector 55, first target 57 comprising a perforated mica sheet 59 backed by a perforated metal signal plate 61, and sheet metal second target 62. The perforated plate electrodes 29-62 are held together as a unit by ceramic or glass tubes or rods 38, 40 passing through their four corners. The rods may be threaded and provided with nuts at either end or if tubes are used insulated bolts may be passed through them, as shown. Insulating spacers 99 fit around the rods or tubes to keep the electrodes in proper spaced relationship. The unitary electrode assembly is carried by rods 30, 32, 34, 36 embedded in the glass base or supported between two mica sheets. There may be as many as four identical electrode structures. The storage elements of the first target are charged individually to collector or cathode potential. If an element is at cathode potential electrons passing through a single open gate in the control grid will be repelled to the collector 55, but if it is at collector potential some electrons strike the dielectric surface and release secondaries which go to the collector 55 while others pass through the aperture 58 and strike the second target 62 which is connected to a suitable indicating output circuit. The signal plate 61 is biased negatively to assist in repelling electrons when the memory element is at cathode potential and also acts to some extent as a shield. In a modification, the collector 55 may be provided with a fine mesh shielding screen, Fig. 4 (not shown). An auxiliary perforated plate shield may be placed against the mica sheet of the first target electrode, Fig. 5 (not shown). It is maintained at a potential between cathode and collector potential and serves to minimize leakage between adjacent storage elements. The first target may be a metal mesh clamped between two perforated metal sheets, Fig. 6 (not shown), and the entire assembly is coated with dielectric secondary emissive material. A shield in the form of a perforated plate may be placed between the first and second target electrodes. In another modification the apertures in the dielectric are conical, or preferably, as shown in Fig. 7, the metal signal plate 61 has conical apertures and has deposited thereon a dielectric material, e.g. an aluminium plate 61 may be anodized'or a metal plate 61 may be covered with silica or with enamel. A perforated negatively biased plate electrode is disposed adjacent to the plate 61. Auxiliary electrodes to properly form the electric fields and to serve as shields may be placed on either or both sides of the first target electrode. In another modification, Fig. 8, flared metal sleeves 74 are inserted in apertures in a metal signal plate 61 and are insulated therefrom by glass or ceramic sleeves 76. A similar construction may be obtained by evaporating metal into the conical apertures of the form of Fig. 7 through a perforated mask. The second target may comprise a perforated metal plate backed by a fluorescent material coated on a mica or glass support, Fig. 9 (not shown). Secondaries released from the fluorescent material are collected by the metal plate. In a further modification, Fig. 10, the first target has an auxiliary negatively biased electrode 80 and the second target is a fine wire 88. Focusing electrodes 82, 84, 86 direct the electrons to the second target. In all forms the electrodes may be flat or cylindrical. The second target electrode may be replaced by one or more electron multipliers within the device. Specification 674,925 is referred to. The Specification as open to inspection under Sect. 91, states that when four sets of electrodes are employed the second accelerating electrode 29, Fig. 1, may be formed of a single sheet bent to form a substantially square enclosure. Additional insulating rods may pass through the perforated plates 29, 35, 55 to space the wires of the control grid networks. This subject-matter does not appear in the accepted Specification.