| 摘要 |
PURPOSE:To reduce dispersion and evaporation of electrode substance and prolong the life of a lamp by using the nonfusible metal having getter action at least for one of the outside coil and the inside coil of an electrode, suppressing formation of impure gas. CONSTITUTION:The electrode of a high pressure sodium lamp is so constituted that the coil 9 consisting of a nonfusible metal wire having getter action such as tantaium is closely wound in 2-4 turns on the introducing side of the electrode core rod 8 made of tungsten or thorium tungsten, and a space is formed between the electrode core rod 8 and the outside coil 9 by winding the wire, keeping a fixed distance from the electrode core rod 8 at the center part. Into the space formed between the inner surface of the outside coil 9 and the electrode core rod 8, the treble inside coil 10 which consists of the nonfusible thin metal wire having getter action such as tantalum having electron radiation substance adhered. |
