A simplified direct-viewing bistable storage tube

A simplified meshless storage tube has been developed which uses a single-layer dielectric storage target deposited over a transparent conductive coating on a glass faceplate. The dielectric layer serves the two principal purposes of bistable charge storage and production of the visible image. The mechanism of writing, storing and erasing depends on the well-known bistability of a good secondary emitting surface under flood current bombardment. The occurrence of an upper and lower stable potential is used here, as in previous bistable devices, to form light and dark image areas having a sharply defined boundary between them. This boundary is, in bistable tubes in general, an inherently unstable region because it has a high gradient across it, which tends to move the boundary across the face of the target. The principal new structural feature of the storage target is the formation of a semicontinuous porous dielectric layer which will not sustain migration of the boundary of the stored charge image transversely across the target surface, because of the electrical and mechanical discontinuity of the target microstructure. Another target is described in which image boundary migration is inhibited by the formation of the target dielectric in a pattern of islands or dots. The semicontinuous layer and the dot target each prevent image spreading and result in a substantial stable range of operating voltages of the collector electrode. The flood current collimating system is described, as is the erase pulse, the split screen, electrical readout, the integration mode, and measurements of the potential on the vacuum side of the storage dielectric. The dependence of brightness, contrast, resolution, writing speed, and stable range on target thickness is also described.