| 摘要 |
PURPOSE: To prevent generation of a leak passage, and stabilize lamp performance by providing a circular seal part between facing surfaces of an end plug and a cap member, and forming one or both of the facing surfaces in such a way that the seal part has a uniform thickness that is preliminarily determined. CONSTITUTION: A facing surface 55 of a cermet cap 56 and a facing surface 57 of an end cap 54 are sealed to each other by a glass seal 58. The glass seal 58 has a circular seal part 62 between the facing surfaces 55, 57 of the cermet cap 56 and the end plug 54, and the circular seal part 62 has a uniform thickness that is preliminarily determined. The thickness of the circular seal part 62 is set to be within 100-300μm. A circular protruded part 64 of the end plug 54 is positioned radially outside the circular seal part 62. The glass seal 58 also has an outer seal 65.
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