Outer seals for shrink-sealed metal halide arc tubes

摘要

A method of producing a metal halide arc tube is provided, in which four seals are made in the arc tube body. Electrode assemblies are inserted and the arc tube body is sealed at one end, blocking contamination from that end. A second seal encloses the electrode assembly nearer the first seal. Halide and mercury doses are introduced into the central arc chamber through the open end of the arc tube body. A third seal is made at the open end at a distance from the arc chamber, reducing vaporization of the doses and contamination of equipment. A fourth seal encloses the electrode assembly nearer the third seal. The electrode assemblies are thus protected and a reflective coating may be applied without electrode contamination. The ends of the arc tube body are then removed, exposing the electrodes. The arc tube is thus provided.