| 摘要 |
PURPOSE:To control cataphoresis phenomenon, by making the cross section of a bulb in a flat form, while linking an anode and a cathode each other at the shorter side of the flat from bulb, and furnishing a bypass to transfer mercury avoiding the short circuit of discharge between the both electrodes. CONSTITUTION:The cross section of a bulb 10 is made in a flat form, and since the shorter sides 10b separated far are less heated than the longish sides 10a close to the discharge route A through the bulb 10, a lower temperature portion is formed at the shorter sides 10b. Furthermore, since a cathode 12 is deflected a little from the center of the cross section of the bulb 10, the shorter side 10b at the side where a bypass 13 is connected is the most apart from the discharge route A forming a lower temperature portion, where the bypass 13 is connected. Therefore, the bypass 13 is at a low temperature condition enough to concentrate the mercury, even when the bulb 10 is lighted, and the returning amount of the mercury from the cathode effect of the cataphoresis phenomenon can be further improved.
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