Flat thin CRT based on controlled electron transport through insulating structures

The feasibility is demonstrated of a flat thin cathode ray tube with insulating supports inside the envelope to withstand the atmospheric pressure. The supports are actively used to guide the electrons from the cathodes to the phosphor screen. The electrons are transported through the insulating structures by a self-regulating secondary emission process, provided a sufficiently high voltage is applied between the entrance and the exit of the structures. The local potentials are automatically adjusted by charge deposition on the insulating walls until a situation is established characterized by the property that the local average secondary emission coefficient is equal to one everywhere in the structure. The flat thin CRT with these insulating internal supports has a thickness of about 1 cm for any display size and a relatively low mass. Large displays have been realized showing a good performance: brightness, contrast, colour purity and power dissipation are comparable to or better than obtained with conventional cathode ray tubes. Some other interesting applications based on the same phenomenon are briefly discussed: an electron ‘fibre’, an electron source with high current density and a beam switch.