Abstract: Fused quartz containing europium oxide, titanium dioxide and cerium oxide has been found to be effective for absorbing UV radiation while transmitting visible light radiation. Uses for this material include lamp envelopes and shrouds for halogen-incandescent lamps and metal halide arc discharge lamps which emit both UV and visible light radiation.

Abstract: Fused quartz containing both titanium dioxide and cerium oxide as UV absorbing dopants has been found to be particularly effective for lamp envelopes for high temperature lamps such as halogen-incandescent lamps and metal halide arc discharge lamps which emit both UV and visible light radiation. The codoped quartz transmits visible radiation and absorbs a substantial portion of the emitted UV radiation. The UV absorption is far superior at temperatures above 500.degree. C. and the codoped quartz does not react with the fill within.

Abstract: In a high intensity metal halide discharge lamp, means are provided associated with the interior surface of the envelope to promote the formation and spreading of a liquid film of condensate thereon. Such a film can lower the color temperature as a result of pressure broadening and self-reversal of the sodium line, and also by acting as a color correcting filter. The film-promoting means may be a coating which imparts an irregularity to the surface such that the reduction in exposed surface area by coverage with a uniform liquid film is energetically favored. Alternatively, a chemically different surface better wetted by the metal halide dose may be used.