| 摘要 |
PROBLEM TO BE SOLVED: To prolong the life of an arc tube with an electrode assembly pinch- sealed to a pinch-sealing part of the arc tube body, the electrode assembly being formed by welding a tungsten electrode and molybdenum foil in a condition that they are partially overlapped with each other, by effectively inhibiting leak from being caused by detachment of molybdenum foil. SOLUTION: By setting an overlap width L1 of a tungsten electrode 26 and the molybdenum foil 30 to satisfy the following equation: 2D<=L1<=0.8 W, where, D is the diameter of the tungsten electrode 26 and W is the width of the molybdenum foil 30, detachment of the molybdenum foil 30 is effectively prevented, while breakage of the molybdenum foil 30 is effectively inhibited. Furthermore, by setting a distance L2 between the molybdenum foil 30 and a discharge space 24 to satisfy the following equation: B<=L2<=0.8A, where A and B are width and thickness of the pinch-sealing part, respectively, growth of electrode crack is effectively prevented, while detachment of the molybdenum foil 30 is effectively inhibited. This effectively inhibits leak from being caused by detachment of the molybdenum foil, thereby prolonging the life of the arc tube.
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