| 摘要 |
PURPOSE:To provide an impregnated cathode of high current density and long life without falling off of coated films by constructing the coated films on the surface of an electron emitter with a multi-layer film alternately coated with osmium and tungsten films. CONSTITUTION:A pellet 1 consists of a porous tungsten metallic substrate of 18-20% in porosity and includes electron emissive materials consisting of barium calcium aluminate in the porous portion. The pellet 1 is brazed to a molybdenum metallic cylinder 2, and in the cylinder a heat source heater 3 is buried with alumina 4. On the top of the pellet, osmium films 5 of 1000 angstrom in thickness and tungsten films 6 of 500 angstrom in thickness are sputtered alternately to produce a multi-layer film 7 of 15000 angstrom in total thickness. The outermost layer is the tungsten film 6. Thereby the osmium density on the electron emitter surface can be kept stable to maintain high electron omission characteristics for a long time. |
