GB795060A - Target structure for barrier grid storage tube - Google Patents

Abstract

795,060. Cathode ray storage tubes. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 20, 1955 [April 23, 1954], No. 11393/55. Class 39(1). The target of a memory storage tube comprises a mica sheet 3, Fig. 2, having a barrier grid 12 of at least one set and preferably two sets of crossing wires on one side and a conductive backing plate 13 on the other side, the surface of the mica sheet 3 in contact with the grid 12 being roughened. A secondary emission collector grid 11 is disposed between the screen and gun. The roughening of the surface of the mica sheet is of the order of a fraction of a MIL, and is achieved by coating the dielectric with a metallic oxide such as MgO or Al 2 O 3 or with a phosphor such as magnesium tungstate or zinc sulphide, or by grinding or lapping the dielectric with one or more of these insulating materials, e.g., Al 2 O 3 . In the latter case Al 2 O 3 particles are pressed into the surface during the lapping operation. If a phosphor coating is used the backing plate is transparent to allow visual observation. The backing plate 13 is an evaporated coating of Al. The collector grid 11 is of tungsten wires making an angle of 45 degrees with the two sets of tungsten wires of grid 12 and a spring 17 presses the mica sheet 3 against wires 12. Grid frames 15, 16 are of ceramic having a matching coefficient of expansion with the grid wires and the entire structure is enclosed in a stainless steel frame 14. Writing is achieved by pulsing the back plate while leaving the beam on the information stored being of binary form as described in Specification 762,294 and during the reading an output is taken from the backing plate. It is stated that noise generated at the back plate during reading, writing, and when the beam is turned off and redistribution of secondary electrons are avoided or reduced by the construction of the invention.