GB1455011A - Electrostatic imaging device and process using same - Google Patents

Abstract

1455011 Image converter tubes AGFAGEVAERT 8 May 1974 [21 May 1973] 24169/73 Heading H1D A device in which a charged particle emission pattern is produced in an envelope containing ionizable gas-by, for example, the incidence of an X-ray, gamma ray, fast electron, neutron, ultra-violet, visible, or infra-red image on a photocathode 1-and is recorded as an electrostatic charge pattern on a conductivelybacked insulating target 3 which is removable from the envelope, includes a structure 2 formed of a plurality of microchannels directed normal to the photocathode surface, having one face adjacent or contacting that surface, and of substantially non-secondary-electron emissive material to prevent the occurrence of self-sustaining discharge, whereby image resolution is improved by the reduction, by the structure 2, of the sideways spread of electrons. The microchannel plate 2 may be formed of corrugated sheets of glass or resin the interior of the channels of which may, except at a photocathode-contacting end, be coated with conductive material, or of metal, in which case photocathode contacting ends may be coated with insulator, or oxidized. The channels are of diameter 10-200 microns, and if the plate is separated from the photocathode the spacing is not more than 1À5 mm. In a modified arrangement (Fig. 4, not shown) the channel plate itself constitutes the photocathode, being formed of lamella or films the wall material of which is photoemissive, e.g. containing lead, uranium, or bismuth in the case of an X-ray sensitive device. The gas filling may be at a pressure above or below atmospheric, and may be a mixture of argon with monobromotrifluoromethane. The envelope is sealed by compressible strips 11 of PTFE.