| 摘要 |
<p>An electrodeless high intensity discharge lamp having an excitation coil (14) disposed about an arc tube (10) includes means for causing a metal halide condensate to form as a protective film on the portion of the arc tube which is nearest the plasma arc discharge during lamp operation. In one embodiment a heat shield (18) is situated on the top and/or bottom thereof. Instead or in addition, the bottom of the arc tube may be concave (Fig.2) to ensure that the condensate does not collect on the bottom of the arc tube. The excitation coil may be situated sufficiently close to the arc tube to ensure that enough heat is removed from the side wall of the arc tube to a heat sink so that the protective metal halide film forms on the inner surface of the arc tube wall. An outer glass envelope is preferably situated (Fig.3) between the arc tube and the excitation coil, which envelope also functions to remove heat from the arc tube side wall. <IMAGE></p> |
