Abstract
The use of the negative glow discharge in neon to provide the basic element of a flat, bright alpha-numeric gas discharge display panel with inherent memory is described. The memory characteristic exploits the property of the individual discharge cells that the voltage required to maintain the discharge is less than that required to strike it. At a holding voltage intermediate between the strike and the minimum maintaining or extinction voltage, every cell will preserve its status of being 'on' or 'off' indefinitely. In this way a message can be built up with a pattern of 'on' cells and stored. Good control of the 'on' current is provided if each cell has a steep positive impedance in the 'on' state. This can be arranged by a careful design of all the cell parameters. Here, however, the choice of a suitable cathode material is shown to be of paramount importance with the graphite form of carbon proving to be the best so far. A complete design theory has been developed by gathering together the relevant ideas, some published for over fifty years, together with new ideas where gaps in our knowledge were apparent. These gaps concerned the boundary effects when the glow is confined within the narrow cell walls and also how to calculate the ionization to be expected when the potential distribution is not uniform. Wherever possible, simple approximate formulae have been found. Also, a graphical technique has been developed to enable the designer to see at a glance how the various parameters interact to give him the desired characteristics. This engineering approach has been used to compare theory with experiment and so predict an optimum design with reduced power dissipation. Xenon gas fillings have also been investigated with a view to reducing the power, and the parameters which affect stability and the working life of the panels have been compared for both gases.