| 摘要 |
It is intended to enable accurate positioning of an electrode top end such that the arc length is constant and prevent leakage from sealing portions due to bending or twisting of a molybdenum foil upon sealing an electrode mount by heating the sealing portion. For attaining the object described above, a quartz bulb (10) in which extension tubes (14A, 14B) each having an inner diameter larger than the inner diameter of the opening of a body tube (11) is welded the openings of both ends of a body tube (11) formed with light emitting portion and a sealing portion thereby forming to a positioning step (15) is used, and electrode mounts 20A, 20B each formed with a positioning engagement portion (24) at a position spaced apart by a predetermined length from the electrode top end are inserted to engage the positioning engagement portion (24) of the electrode mounts (20A, 20B) to the positioning step (15) and, in this state, the sealing portions (13A, 13B) are sealed.
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