Abstract: A lamp is provided having an arctube having a light-transmitting envelope. The arctube is surrounded by a gaseous medium confined by a containment envelope such as a hermetic shroud. The gaseous medium is preferably He or H2 or Ne or another gas whose thermal conductivity is greater than that of N2 at 800° C., or a mixture thereof, to help cool the arctube. The inside and/or outside of the shroud may be coated with a diffusion barrier. To help cool the hot spot of the arctube the gap between the shroud and the envelope can be made small, the portion of the shroud wall near the arc can be thickened, the arctube can be offset above the longitudinal axis of the shroud, and the return lead of the arctube can be located between the shroud and the arctube.

Abstract: A ceramic arctube for use in a high intensity discharge lamp. The arctube includes a ceramic light transmitting tube which surrounds the arc. The light transmitting tube has two or more features selected from the group consisting of (a) an inner diameter less than 2.6 mm, (b) a wall thickness of less than 1.4 mm, (c) an average grain size of greater than 20 microns or less than 5 microns or real in-line transmission (RIT) greater than 20%, and (d) an inner surface or outer surface having an Ra value less than 100 nm. These features lead to a smaller apparent size of the arc source and less scattering of light, resulting in improved performance of the arctube in a reflector lamp.

Abstract: A ceramic arctube preferably for a high pressure discharge lamp. The ceramic arctube can have an anti-reflection interference coating on the outside or inside surface of the bulb section of the arctube. The outside and/or inside surface of the outer wall of the bulb section of the arctube can be substantially spherical to increase efficiency. The wall thickness of the outer wall of the bulb section can be shaped to lens rays from the arc toward a preselected region of a reflector optically coupled to the arctube to increase efficiency.

Abstract: A binder system for forming a ceramic body, such as a translucent arc tube for a metal halide lamp, comprises a hydrocarbon, such as a paraffin wax, a copolymer, such as poly (ethylene-co-vinyl acetate), and optionally a surfactant. The binder system is mixed with a ceramic powder and heated to above the melting point of the binder. The heated mixture is formed into a compact having the general shape of the finished ceramic body and then cooled or allowed to cool. The hydrocarbon and copolymer have overlapping freezing points so that when the shaped compact cools, crystalline segments of the copolymer (such as ethylene segments) co-crystallize with the hydrocarbon, while amorphous segments (such as vinyl acetate) form bridges between the crystalline regions. As a result, the cooled compact has improved green strength over conventional binder systems.