| 摘要 |
PURPOSE:To prevent any blackening of a metal halide lamp by charging an emission tube with gas containing a given amount of oxygen gas, and removing tungsten adhering to the wall of the tube by means of the said oxygen gas so as to clean the inside of the tube. CONSTITUTION:An emission tube 1 made of quartz, which contains electrodes 2a and 2b made of tungsten, is charged with given amounts of mercury, a halide of a rare earth metal, and argon gas. At the same time, it is charged with oxygen gas at 0.3-5Torr. During the long period of lighting, tungsten adhering to the wall of the tube 1 binds to both isolated iodide and charged oxygen to produce WO2I2. Next, WO2I2 produced is evaporated from the wall of the tube 1, travels along the convection and reaches near the electrode 2a placed in the lower part of the tube 1, and is decomposed due to the high temperature of the electrode 2a. Then, the product of the above decomposition is sent back to the electrode 2a. Consequently, since the wall of the tube 1 is cleaned all the time, any generation of the backening phenomenon of a metal halide lamp can be prevented, and the maintenance rate of the luminous flux of the lamp can be enhanced. |
