| 摘要 |
PROBLEM TO BE SOLVED: To protect an arc tube by forming a thin film of excessive metal halide liquid on an area which is subject to arc corrosion most in the arc tube. SOLUTION: This electrodeless high intensity discharge lamp 10 includes a transmissive arc tube 12 for housing plasma arc discharge. The arc tube 12 includes a top 14, a bottom 16, and a side wall 18, and filling is arranged inside the arc tube 12. The filling includes at least one kind of metal halide and buffer gas. The arc tube 12 has a wall and an inner surface of the wall includes a ring shaped area around a central range of the side wall. The main area of the central range of the inner surface of the arc tube wall is smooth but includes a rough surface for settling liquid in the ring shaped area.
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