GB1061986A - Image storage system - Google Patents

Abstract

1,061,986. Cathode-ray storage tubes. WESTINGHOUSE ELECTRIC CORPORATION. Nov. 21, 1963 [Dec. 3, 1962], No. 46027/63. Heading H1D. The target of a fast response storage tube includes a porous insulating layer-e.g. of 1- 5% of the bulk density-having one face exposed to a potential stabilizing reading electron beam, and the other contacting an electron - transmissive conductive film upon which a writing electron beam impinges to produce secondary electrons in the porous material. As operated, a charge pattern corresponding to the written information is produced on the exposed surface by a combination of secondary emission from that surface, and of " secondary electron conduction," i.e. the movement of secondary electrons through the porous layer by way of the voids rather than by solid state conduction in the insulating material. The electron image produced by a caesium/antimony photocathode 14 (Fig. 1, not shown) is focused upon the aluminium film (34) which is supported in a nickel, iron, or cobalt ring (32) and itself supports a porous layer (36) of potassium chloride, magnesium chloride, or magnesium oxide. A nickel grid (40) collects the secondary electrons emitted from the surface of layer (36), which is scanned by a low-velocity electron beam from gun (20) to stabilize it at gun cathode potential, whereby a positive bias voltage applied to layer (34) maintains a low field across the porous layer such that the remaining secondary electrons produced in layer (36) are collected by layer (34). A further grid (Fig. 3, not shown) may be introduced between collector grid (40) and layer (36), to prevent the surface of the latter from attaining a potential with respect to the gun cathode greater than the first cross-over point of the layer material, with consequent breakdown and destruction of the latter in the resulting high field. The porous layer may be produced by evaporation of potassium chloride in argon at reduced pressure. Modifications referred to include the substitution of a scanning electron beam for the photo-cathode (14), to provide a scan converter tube, and the disposition of both read and write electron guns on the same side of the storage target. Reference has been directed by the Comptroller to Specifccation 911,560.