To efficiently apply irradiation of an ultraviolet-ray even at a low pressure.
A discharge space 2 is formed in a hollow part in the inside of a permeable vessel 1. Any starting gas of argon, krypton, xenon or neon and any of iodine, fluorine, chlorine or bromine are sealed with mercury in this discharge space 2. A helical electromagnetic induction coil 6 is wound to the periphery of the permeable vessel 1 of an electrodeless discharge lamp 5. A current is supplied to the electromagnetic induction coil 6 from a high frequency generating device, a discharge is generated in the discharge space 2 by high frequency energy, irradiation of an ultraviolet-ray of 254nm wavelength of strong sterilizing and purifying action is applied. Silver is easily coupled with halogen rather than oxidized, mercury halide coupled with halogen is easily vaporized due to a high vapor pressure, to be again seperated in an arc and active as a mercury atom, so as to prevent mercury oxide from sticking to an internal surface of the permeable vessel 1, generation of its blackening is prevented.
KUGA KEISUKE
INOUE AKIHIRO
KAMIMURA KOZO
