| 摘要 |
The luminescent brightness of discharge tubes is improved by increasing the current density of the tube current. A discharge tube (1) is provided with a bulb (2) which comprises opposite ends (2a) each having an electrode (4) and being of circularly annular sectional shape, an intermediate section (2b) which is of non-circularly annular sectional shape, which is formed between the opposite ends (2a) and which is smaller in radial cross-sectional area than the opposite ends (2a), and a connecting section (2c) for connecting the opposite ends (2a) with the intermediate section (2b). Since the intermediate section (2b) of non-circularly annular sectional shape is smaller in sectional area than the opposite ends (2a) of circularly annular sectional shape, the current density of the tube current flowing through the intermediate section (2b) between the electrodes (4) increases over conventional bulbs, making it possible to improve the luminescent brightness of the discharge tube (1). Further, since the electrodes (4) of conventional circular sectional shape can be disposed in the opposite ends (2a) of circularly annular sectional shape, the electrodes (4), which are inexpensive and of general circular sectional shape, can be used.
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