| 摘要 |
PROBLEM TO BE SOLVED: To provide a metal halide lamp which can control lighting, wherein the metal halide lamp has such a function that it can stop safely and rapidly a discharge in an outer tube when the discharge occurs in the outer tube. SOLUTION: A metal halide lamp comprises a luminous tube 1 in which at least sodium halide and scandium halide are sealed, an outer tube 3 which surrounds the luminous tube 1 and has an almost vacuum inner space, and a coldest temperature keeping means for keeping the coldest temperature of the luminous tube 1 at not less than 550 deg.C when the lamp is lighted using such a lamp power that is 50% of a rated lamp power, wherein the outer tube 3 is equipped with a discharge in outer tube stopper means for stopping discharge which occurs in the outer tube. The discharge in outer tube stopper means is equipped with an atmosphere introduction means. The atmosphere introduction means comprises a pair of conductive projections 21A, 21B and a glass tube 20 which is provided close to the projections for introducing the atmosphere.
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