DISCHARGE VESSEL, ELECTRODELESS METAL HALIDE DISCHARGE LAMP, LIGHTING DEVICE FOR THE LAMP, AND LIGHTING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an electrodeless metal halide discharge lamp free of drop of the starting characteristic, unlikely to generate swings or stall of arcs and involving less drop of the arc efficiency and electric characteristics by deciding the encapsulated amount of tin halide to the optimum range in relation to the coldest part temperature of an air-tight vessel during lighting. SOLUTION: Besides halides of light emitting metal, tin halide no more than 0.012e0.005A (μmol) per cc internal capacity where the coldest part temperature of an air-tight vessel 1a during lighting lies in the range 650-950 deg.C, for example SnI2, is encapsulated in the vessel 1a. The tin halide increases the total vapor pressure of metal halides and decreases the existence probability of ions of the simple substance of encapsulated metal near the tube wall, and further SnI2 absorbs free halogen to be oxidated into SnI4, etc., so that the free halogen can be removed. Because the tin halide is not encapsulated excessively, the system involves less drop of the arc efficiency and electric characteristics.