| 摘要 |
PROBLEM TO BE SOLVED: To provide a double tube low pressure mercury vapor discharge lamp that resolves a problem of shock resistance by preventing the increase of thermal history of a light transmissive discharge container and for which the ratio of its effective light emission length to the total lamp length is increased and provide a lighting system using it. SOLUTION: A slender transmissive discharge container 1 which encloses a couple of electrodes 3 at both its ends, and seals an ionized medium containing a mercury or rare gas inside, and for which a pair of lead-in wires 4 are extended outside from its both ends is incorporated into an outer tube 5, and a distance(d) between an outside end face 5E at least at one end of the outer tube 5 and an outside end face 1E at the opposite end of the translucent discharge container 1 is set to 1-5 mm. The distance(d) between the outside end face 5E and the outside end face 1E at the opposite end of the transmissive discharge container 1 can be formed as above at both ends of the outer tube 5. While the distance(d) between the outside end face 5E and the outside end face 1E at the opposite end of the transmissive discharge container 1 is formed at the one end of the outer tube 5 as above, the outer tube 5 and the transmissive discharge container 1 may be welded together when the other end is used as an exhaust side.
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