| 摘要 |
PURPOSE: To realize high luminous efficiency and satisfactory illuminance stability in order to lengthen the life of a short arc type discharge lamp used for an aligner for IC, etc. CONSTITUTION: Mercury and rare gas are enclosed in the inside 21 of an arc tube 1. The rare gas is obtained by mixing relatively low molecular weight rare gas, such as helium and neon, into relatively high molecular weight rare gas, such as xenon, krypton and argon, at a volume ratio of 5-40%, under a pressure of approximately 2 atmospheres or more at an ordinary temperature. A positive electrode 3 comprises a cylindrical body 14, a tapered portion 13, and a flat tip portion 12.
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