| 摘要 |
PURPOSE:To shorten the activation time by providing a thin film layer using BaO or BaCO3 as the main component on the surface of an impregnated cathode provided with a mixed layer containing W and Sc2O3. CONSTITUTION:An electron emitting material 2 such as 4BaO.CaO.Al2O3, 5BaO.2CaO.3Al2O3, etc., is impregnated into a heat-resistant porous substrate 1 made of W or using W as the main component and its fine holes as an impregnant. A mixed layer 3 made of W and Sc2O3 is deposited. A thin film layer 7 using BaO or BaCo3 as the main component is formed on it by the spattering or CVD method. A base material impregnated cathode provided with the layer 3 is heated by a heater 6, thereby the porous W and the electron emitting material 2 are reacted to generate Ba, and Ba passes fine holes and reaches the surface of the cathode. On the other hand, Sc and O are diffused to the surface, and Sc and O are combined to form a low-work function layer. It takes time to form the (Ba, Sc, O) layer, thus electron emission is supplemented by the layer 7 during this time. |
