| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp of easy manufacturing, in which carbon and hydrogen elements are not brought about and the maintenance of a stable color and light convergence is possible under the optical system in a long hours in an abundant sealed halogen atmosphere. SOLUTION: In this discharge lamp, alkali included in it as impurities is specified to lithium or/and sodium, and equipped with a tungsten electrode with alkali concentration of 75 ppm or less and a discharge container in which the total alkali component in the quartz glass is 0.6 ppm or less. The amount of halogens contained is arranged around 1.1×10-4 to 3.2×10-3μmol/mm3.
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