Patent GB-882465-A (GB)
Title: An electrostatic signal storage device
IPC: H01J31/60
Filed: 1958-06-06
Abstract: 882,465. Cathode-ray storage tubes. TELEFUNKEN G.m.b.H. June 6, 1958 [June 8, 1957], No. 18156/58. Class 39(1) [Also in Group XIX] An electrostatic signal storage device, e.g. for use in electronic computers, comprises a target formed by a signal electrode 8, Fig. 1, carrying a storage layer 6, the whole surface of which is simultaneously and continuously bombarded by electrons, and a grid barrier consisting of parallel wires arranged in two parallel planes 9a, 9b so that the wires of one plane are perpendicular to the wires of the other plane, the wires in each plane being subdivided into groups of at least two adjacent wires electrically connected together. The grid barrier is diposed parallel to and at a small distance in front of the storage layer, this distance and the dimensions of the grid barrier being so chosen that the energy of primary electrons reaching the storage layer depends both on the potential of the grid barrier and on the charge condition of the individual storage elements. As shown, a further grid 12 may be arranged in front of the grid barrier to level the electric field between the electron gun and the grid barrier. The storage layer may comprise a plurality of discrete metallic elements 6 on an insulating layer 7 or a single dielectric layer. The wires in each plane of the barrier grid may be arranged as shown in Fig. 6b, each selector grid being formed by a wire strung in a plurality of loops over pins in an insulating frame 40. The openings of grid system 9b may be larger than those of system 9a to obtain a sufficiently high charge penetration effect of the positively charged storage regions. The signal to be stored consists of either a zero or a one. In operation a high negative voltage UN, Fig. 3a may be applied to all the selector grids while they are not involved in a writing or reading process, the voltage being such that no electrons can pass the grid barrier. A one is written by applying a high positive voltage Us to the appropriate selector grids, the voltage being such that primary electrons impinging on the storage element concerned are capable of releasing secondary electrons in a ratio greater than one so that the storage element becomes positively charged. The stored charges are however liable to be reduced by ionic or insulation currents so that this mode of operation can only be used for short storage periods. To obtain longer storage periods a positive potential U H  is applied to all selector grids while they are not involved in a reading or writing process. This voltage is such that electrons reaching the storage layer release secondary electrons in a ratio which is only just less than one, so that the charge of a storage region on which a one has been written is automatically stabilised at a potential 1 to 2 V more positive than the potential U H . The elements on which a one has not been written are stabilised at earth or cathode potential indicating that a zero has been written. The stored signals are read out by applying a small positive potential U 2  to the selector grids, this voltage being such that electrons reaching the storage layer release secondary electrons in a ratio considerably less than one. If a zero is stored no electrons reach the storage layer and no signal is produced but if a one is stored a transverse current flows through the resistance 17 and a signal is produced, the charge on the storage element being removed.