| 摘要 |
A mercury lamp (A) of the short arc type in which tantalum (9) can absorb impurity gases to a sufficient degree even if the inside of the arc tube reaches a high temperature is achieved by providing an arc tube, within which mercury and an inert gas are encapsulated, with a pair of electrodes (2,3) disposed opposite each other within the arc tube, each of the electrodes (2,3) being supported by a respective terminal post (4,5), tantalum (9) being provided on the terminal post (4) of one of the electrodes (2), and by ensuring that both of the relationships (D2/D1) ≥ 1.3 and 0.2 ≤ (D2/D1)<2>/L ≤ 0.5 are satisfied at the same time, where D1 is an outer diameter of the terminal post (4) in millimeters, D2 is an outer diameter of the electrode (2) supported by the respective terminal post (4) in millimeters, and L is a distance between a tip of the electrode (2) on which the tantalum (9) is provided and the tantalum (9) on the terminal post (4) of that electrode (2).
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