Abstract
In contrast with Part I, of a paper entitled “Bright Light Sources,” read before this Society on November 14, 1944, in which incandescent tungsten filament projector lamps were discussed, the present paper deals specifically with high brightness electric discharge lamps. Attention is directed to considerations of those factors wihich influence the brightness of the electric discharge and reference ismade to certain definte types of lamp which have emerged in the last few years, as well as to a number of types which are still in the experimental stage. To enable the discharge of an electric current to produce a light source of high brightness some or all of the following conditions must obtain in the arc: (a) High luminous efficiency; (b) high voltage gradients; (c) high current density. The inter-relation of these three factors is discussed. Both air-cooled and water-cooled mercury vapour lamps are described and some details are given of their properties and uses. Attention is drawn particularly to the 500 and 1000-watt ME air-cooled compact source mercury vapour lamps. Progress in the development of ME-type lamps up to about 15 kws. is outlined, and some of the factors which governed various stages in the development are described. The second section of the paper deals with low-pressure gas discharge lamps. The essential circuit components for operating high brightness condenser flash lamps of this type are described. The magnitude of the discharge currents and lumen outputs which can be obtained are indicated. Some applications of condenser flash discharge lamps are mentioned.
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