In a cold cathode consisting of a layer of aluminum oxide between a plate and a grid, the aluminum oxide is formed on aluminum as a porous oxide layer. The meshes of the grid are so fine that the grid is attracted against the oxide due to the voltage difference with the plate.
A discharge device (10) is disclosed which is capable of providing preionizing ultraviolet wave length photons to the area of a gap between the first (15) and second (35) electrodes of the device. The first electrode (15) includes a core (20) of dielectric material, a conductive plate (23) mounted on one surface of the core, and a conductive grid (26) mounted on an opposed surface of the core which faces the second electrode. The application of a negative voltage pulse to the grid (26), while the plate (23) is maintained at substantially ground potential, causes electrons to discharge between the conductors of the grid and the adjacent surface of the dielectric core, and, in doing so, generates photons having wavelengths in the ultraviolet range. The ultraviolet photons, which are emanated in a two dimensionally uniform pattern over the surface of the dielectric core adjacent the grid, cause ionization of the gas within the main discharge gap between the first and second electrodes. The second electrode may be maintained at ground or other potential higher than the grid such that a sufficient potential difference reached between the second electrode and the grid after the preionization will result in a uniform glow discharge of electrons between the two electrodes. This glow discharge is useful for the firing of gas lasers and in certain chemical reactors, such as ozone generators.
A high intensity discharge lamp includes a dielectric substrate, a first electrode near the dielectric substrate, a second electrode spaced from the first electrode and near the dielectric substrate, a conductor spaced from the dielectric substrate, and adapted to provide a current return from one of said electrodes to an electrical driver circuit, and at least one metal element near the dielectric substrate. The electrical driver circuit is constructed to produce an electric potential sufficient to cause an electrical breakdown of a medium between the electrodes. The lamp and metal element are also arranged to enable a coolant to flow adjacent to at least one surface of the dielectric substrate to transfer heat from the dielectric substrate to the coolant.
