Metal vapor discharge lamp and lighting apparatus capable of stable maintenance of characteristics

摘要

A metal vapor discharge lamp including an arc tube 1 that includes a container 10 and power transmission members 20a and 20b. The container 10, made of translucent ceramic, is divided into a main tube portion 11 and narrow tube portions 12a and 12b extending out from both ends of the main tube portion 11. The power transmission members 20a and 20b respectively include electrode pins 21a and 21b made of tungsten. Coils 22a and 22b made of tungsten are respectively wound around ends of electrode pins 21a and 21b, which are respectively joined with electrode supporting members 23a and 23b made of conductive cermet. Electrode length L1 is set to (0.041P+0.5) mm to (0.041P+8.0) mm, "P" representing a lamp power in watts. Alternatively, a narrow tube portion length L2 is set to (0.032P+3.5) mm to (0.032P+8.0) mm inclusive.