| 摘要 |
PURPOSE:To prevent an escape of sodium sealed in a luminous tube by positioning the luminous tube, in which at least halide sodium is sealed, below the central axis of an outer tube consisting of a straight bulb and arranging a luminous tube lead wire parallel to and above the luminous tube. CONSTITUTION:A pair of main electrodes 6A and 6B are opposedly arranged on both end sealing parts of a luminous tube bulb 5 made of quarz glass in a luminous tube 3 in which, a rare gas for starting, mercury and a metal halide, for example, scandium iodide and sodium iodide are sealed. On main electrode 6B is connected to a base 2 through a lead wire 7 and the other main electrode 6A is connected to the base 2 through a lead wire 8 arranged in a position parallel to the longitudinal direction of the luminous tube 3 and as distant as possible from the luminous tube 3. Thereby, a quantity of photoelectrons emitted from the luminous tube lead wires 7 and 8 caused by the rays of light radiated from the luminous tube 3 can be suppressed and also an escape of sodium ions sealed in the luminous tube to the outside of the luminous tube can be prevented.
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