| 摘要 |
PROBLEM TO BE SOLVED: To increase luminous efficiency, to efficiently feed electric power to a discharge space and to make a uniform and stable electric discharge by providing a trigger electrode and an inner electrode with two slit sections in the whole length direction of the tube axis in a tube with a high electric insulation property, applying a high frequency in a specific range, and making a field electric discharge. SOLUTION: When the anglesθ1,θ2 of two slit sections are set to 90 deg., the most right/left symmetrical electric discharge is attained. The position of plasma in a discharge container 1 can be controlled by changing the anglesθ1,θ2. When the lighting frequency of a lamp is high (radio frequency of 1-100 MHz), the probability that excited rare gas atoms meet other atoms is increased even if the discharge gas pressure is low. The discharge container 1 is sufficiently cooled than the center section of the lamp, the discharge gas is also cooled, and the luminous efficiency of ultraviolet rays is further improved. Since the discharge gas pressure of the lamp is low, the discharge start voltage becomes low, and the starting property of the lamp is improved.
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