Gas discharge lamp having an electrode with a low heat capacity tip

摘要

An electric gas discharge lamp includes an electrode having a tip portion comprised by a mesh body carrying an emitter material. The mesh body in a favorable embodiment is circular cylindrical and is attached via an electrically conductive thermal isolator to a conductive feed-through, such as a hollow ferrule, extending through a seal of the lamp vessel. As compared to a continuous walled tip portion of similar shape and material, the mesh body has a lower mass and heat capacity, and can therefore be operated at higher temperatures without increasing the temperature of the seal area. The higher operating temperature of the tip portion promotes greater electron emission from the emitter material, and therefore a lower cathode fall. A lower cathode fall enables the lamp to be operated at higher lamp currents for greater light output. The mesh body also has the capability to reduce sputtering from the electrode through improved adhesion of the emitter material to the tip portion and faster attainment of its nominal operating temperature as compared to a smooth continuous walled body. In a favorable embodiment, the lamp is a low pressure discharge lamp having an inside diameter of less than about 5 mm.