| 摘要 |
PURPOSE:To prevent the direct flowing of electron beams to a grid electrode and simplify the structure of an electron gun unit, by composing the grid, of a ceramics with numerous electron beam permeable holes, and a metallic layer formed at the side opposite to a ceramic cathode, and furnishing it contacting to the cathode. CONSTITUTION:At the rear side of a spherical cathode 1 radiating electron beams, a heater 2 is furnished, and at the surface to radiate the electron beams of the spherical cathode, a spherical grid electrode 10 is contacted. This spherical grid electrode 10 has a thin ceramic base plate 11 where necessary electron beam permeable holes are furnished, and then the reverse side from the cathode is metallized and coated thickly to form a metallic layer 13. The electron beams radiated from the cathode 1 heated by the heater 2, pass through the numerous beam permeable holes furnished at the grid electrode 10 axis-symmetrically, and pulse-modulated. The pluse-modulated electron beams are focused by a focus electrode 5, accelerated by an acceleration electrode 6, pass through a drift tube 9, and finally reach to the collector.
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