| 摘要 |
To realize high irradiation efficiency and intensity stability for extending lifetime of the short-arc discharge lamp to be used for IC exposure apparatus or the like. For this end, mercury and rare gases are sealed in the inner space 21 of the discharge tube 1. The rare gases are a mixture of a relatively high molecular weight rare gas such as xenon, krypton, argon, etc. and 5%-40% by volume of a relatively low molecular weight rare gas such as helium, neon, etc. And pressure of the mixed rare gases is set to 2 atmospheric pressure or higher. The anode 3 comprises the columnar body portion 14, the tapered portion 13 and the flat portion 12.
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