| 摘要 |
PURPOSE:To prevent an excessive rise in a temperature of amalgam so as to suppress a mercury vapor pressure by extending terminal parts which are not sealed with electrodes in U-shaped bulbs so as to form extension parts and housing amalgam in these extension parts. CONSTITUTION:A plurality of U-shaped bulbs 14a to 14c are connected to each other at laterals of their terminal parts so as to compose one discharge path. Terminal parts which are not sealed with electrodes 1 5 in the U-shaped bulbs 14a to 14b are extended to form extension parts 17, and amalgam 20 is housed in these extension parts 17. Since the extended part position is little subject to heat generation of the electrodes 15 during lighting and distant from the discharge path, a rise in temperature becomes small. Hence, the temperature of amalgam 20 can be kept in an optimum range and a mercury vapor pressure can be effectively suppressed.
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