| 摘要 |
PROBLEM TO BE SOLVED: To support a discharge tube with a simple structure. SOLUTION: A double tube structured discharge tube 11 formed by an outer tube 11a and an inner tube 11b is supported by flanges 13b1 and 13b2 in which a tip end of the inner tube 11b longer than the outer tube 11a constitutes an envelope 13 and is housed in the envelope 13 closely shielded so that flow water 100 invades. Thereby, since the discharge tube 11 is never moved mechanically stabilized in the envelope 13, the discharge tube 11 is never damaged, and flow water does not come into direct contact with the discharge tube 11. When a high-frequency current is supplied to an excitation coil 12 wound around an outer periphery of the outer tube 11a through the lead wire 15 and a discharge tube is lit, a tube wall of the discharge tube 11 is held at approximately 40 deg.C due to a heat generated from the discharge tube 11 and a heat effect of the envelope 13, ultra-violet rays are effectively irradiated from mercury in the discharge tube 11, and a sufficient quantity of ultra-violet rays are irradiated in flow water 100. |
