| 摘要 |
PURPOSE:To make it unnecessary to liquefy the metallic vapor and prevent from the contamination, by making an alkaline metallic vapor permeate into a porous body and forming the porous body with a melting point higher than the ionization temperature of the metallic vapor as a part of a vapor tank. CONSTITUTION:A cesium tank 4 to store the metallic cesium has a porous body 6 as an emitter at its top and the cesium metallic vapor is permeated into the porous body, while the porous body 6 is made of tungsten whose melting point is higher than the ionization temperature of the cesium metallic vapor. The cesium metallic vapor scatters in the cesium tank 4, and flows in the porous body 6 passing through orifices 5'. On the other hand, the porous body 6 is heated by the electron shocks from a filament 8, and, the cesium vapor is ionized by the surface ionization and drawn out by a drawing out electrode 11 as ion beams 12. Since the alkaline metallic vapor is protected by the vapor tank in such a way, and not leaked to the ion drawing out device side, the alkaline metallic vapor is not required to liquefy, and prevented from contamination.
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