| 摘要 |
<p>A low-wattage metal-halide discharge lamp (10) has a quartz tube (12) of the double-ended type that forms a bulb (14) or envelope, a pair of electrodes, e.g., an anode (30) and a cathode (32), which penetrate into an arc chamber (16) inside the envelope (14), and a suitable amount of mercury plus one or more metal halide salts. The electrodes (30, 31) are each formed of a refractory metal, i.e., tungsten wire, extending through the respective necks (22, 24) into the arc chamber (16). Heat dissipation through the neck (22, 24) is controlled by constructing the quartz shanks (26, 28) so that they have shank segments of a desired surface area that extend from the necks (22, 24) a distance equal to the length (50) of the arc chamber (16). A shank segment loading factor is defined as the rated power divided by the shank segment surface areas, and should be in a target range of 12 to 36 w/cm-2. Lamps of this design achieve high efficacy at relatively low power, i.e., below 30 watts.</p> |
