CATHODE FOR DISCHARGE TUBE

摘要

PURPOSE: To provide a negative electrode which has a long life time by shortening a heating time through setting a thickness of a support base to be a predetermined value and a size of metal crystal to be equal to or larger than that value. CONSTITUTION: A cathode 1 has a cylinder-like nickel/chrome negative electrode shaft 2 containing a support base 3, the shaft 2 accommodates a helical filament 4, and an electron-emitting material layer 7 of a few tens of μm is arranged on the base 3. And the shaft 2 is suspended and fixed to an opening of an outer casing 6 using suspension means 8a-8c, and the filament 4 is connected to current-supplying conductors 5a and 5b. Further the filament 4 is arranged in the interior of the shaft 2, wherein a distance (d) between the base 3 and the filament 4 is in a range of 20μm-300μm.