| 摘要 |
PURPOSE:To prolong the life of an electrode, simultaneously save its preheat current and shorten the length of its lighting time, by forming a layer of thermion emitting material on surfaces of a plate-shaped base material where a narrowed width portion is constructed. CONSTITUTION:A narrowed width portion 10 is constructed in the central part of a thin plate 11 made of tungsten on surfaces of which a thermion emitting material 12 is processed a sputtering. The width-narrowed portion 10 permits its resistance value to be higher than that of both end parts of said plate and its temperature to easily rise higher. Accordingly, if conditions at end parts of the thin plate 11 are made the same as those for a rectangular thin plate 8, the width-narrowed portion 10 can permit an electrode to reach the arcing voltage by a less preheat current. |
