| 摘要 |
PURPOSE:To accelerate the transition to arc discharge by using as opposing pair of electrodes of a metal halide lamp, those electrodes which are constituted by winding a double coil with a coil outside diameter of (D) around an electrode core with a diameter of (d). CONSTITUTION:A prescribed amount of mercury, a starting rare gas such as argon, and metal halide such as scandium iodide or sodium iodide etc are sealed in a luminous tube 2 provided with opposing pair of main electrodes 4a, 4b and a starting auxiliary electrode 5 to form a metal halide lamp. The main electrodes 4a, 4b are constituted by winding a double coil 11 made of pure tungsten around an electrode core 10 made of tungusten containing 2% of thorium. Where, D>=1.8mm., D/ d>=2.5, and h>=2mm. are satisfied. Thus, the transition to arc discharge is made sure and rapid, and the starting period can be shortened. |
