| 摘要 |
A dispenser cathode is fabricated by covering a reservoir of electron emitting material with a perforated metal foil having an appropriate pattern of pore-sized apertures thereon for providing uniform electron emission from the cathode surface. The electron emitting material is in the form of a pellet of barium oxide impregnated with a wax or resinous material to minimize chemical reduction of the barium oxide in air. The impregnated barium oxide pellet is sandwiched between the apertured foil and a support structure to which the foil is welded. During tube bake-out or subsequently during cathode activation, the wax or resinous material evaporates and barium oxide migrates through the apertures to cover the surface of the foil in a uniform manner. The desired pattern of apertures in the foil is achieved by photolithography, or by forming the foil (e.g., by chemical vapor deposition, sputter deposition, evaporation, or sintering) on a substrate containing an array of protruding posts. With the photolithographic technique, the desired pattern of apertures is chemically etched directly on the foil; and with the technique in which the foil is formed on a substrate having an array of posts, the substrate with its protruding posts is removed by chemical etching after the foil has been formed. With either technique for forming the apertures, a shadow grid can also be formed as an integral part of the cathode surface by depositing a layer of reactive material such as zirconium or graphite on a selected portion of the cathode surface. This layer of reactive material prevents the formation of an emitting layer of barium oxide on a selected pattern on the cathode surface.
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