| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp and an illumination device using it wherein thermal deterioration of related members such as a reflector or the like is made difficult to occur by reducing a temperature of a tube wall in the vicinity of an internal electrode. SOLUTION: This is equipped with a discharge container 1 constituted in such a way that the internal electrode 1c of a length L (mm) in the tube-shaft direction is sealed and enclosed at least in one end of a slender and translucent air-tight container 1a, and that a discharge medium having rare gas as its main substance is sealed inside, and with the external electrode 2 wherein an electroconductive substance of a width r (mm) is formed in a coil form along the longitudinal direction of the light- transmissive air-tight container 1a and almost in contact with an outer peripheral face, wherein the winding number N (convolution) satisfies a formula 0<=N<=0.25×L/r in a region opposing to the internal electrode 1c of the light-transmissive air-tight container 1a and wherein a discharge is made to occur between the internal electrode 1c and it. By this, because the temperature of the tube wall in the vicinity of the internal electrode 1c is reduced, the thermal deterioration of related members such as the reflector or the like nearby arranged and installed becomes difficult to occur.
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