Abstract: A lamp includes a discharge vessel. Tungsten electrodes extend into the discharge vessel. An ionizable fill is sealed within the vessel. The fill includes a buffer gas, optionally free mercury, a halide component which includes a rare earth halide selected from the group consisting of lanthanum halides, praseodymium halides, neodymium halides, samarium halides, cerium halides, and combinations thereof. A source of available oxygen is present in the discharge vessel. The rare earth halide is present in an amount such that, during lamp operation, in combination with the source of available oxygen, it maintains a difference in vapor phase solubility for tungsten species between a wall of the discharge vessel and at least a portion of at least one of the electrodes.

Abstract: A lamp includes a discharge vessel. Tungsten electrodes extend into the discharge vessel. An ionizable fill is sealed within the vessel. The fill includes a buffer gas, optionally free mercury, a halide component which includes a rare earth halide selected from the group consisting of lanthanum halides, praseodymium halides, neodymium halides, samarium halides, cerium halides, and combinations thereof. A source of available oxygen is present in the discharge vessel. The rare earth halide is present in an amount such that, during lamp operation, in combination with the source of available oxygen, it maintains a difference in vapor phase solubility for tungsten species between a wall of the discharge vessel and at least a portion of at least one of the electrodes.

Abstract: A lamp includes a discharge vessel. Tungsten electrodes extend into the discharge vessel. An ionizable fill is sealed within the vessel. The fill includes a buffer gas, optionally free mercury, a halide component which includes a rare earth halide selected from the group consisting of lanthanum halides, praseodymium halides, neodymium halides, samarium halides, cerium halides, and combinations thereof, a source of available halogen. The discharge vessel optionally includes a source of available oxygen. The source of available halogen and optional source of available oxygen are present in an amount such that the vapor phase solubility of tungsten species in the fill during lamp operation is lower adjacent at least a portion of one of the electrodes than at a wall of the discharge vessel, such that tungsten deposited on the wall during lamp operation is transported back to the electrode.

Abstract: A method for forming a porous carbonaceous preform includes forming a mixture comprised of up to about 50 volume percent of furfuryl alcohol or tetrahydrofurfuryl alcohol, about 1 to 10 volume percent of a nonionic polyethylene oxide polymer ranging in molecular weight from about 100,000 to 5,000,000, about 30 to 80 volume percent of a carbonaceous material, and the balance water. The mixture is cast to form a body, and heated to decompose the polymer and form the porous preform. A molding composition for carbonaceous material includes, up to about 50 volume percent of furfuryl alcohol or tetrahydrofurfuryl alcohol, about 1 to 10 volume percent of a nonionic polyethylene oxide polymer ranging in molecular weight from about 100,000 to 5,000,000, about 30 to 80 volume percent of the carbonaceous material, and the balance water.