| 摘要 |
A thermionic cathode for discharge lamps is a two part structure consisting of a wire stem bearing a cup at its end, the cup being a receptacle for an electron-emitting composition and ensuring that electrons can only issue from the mouth of the cup and not by passage through the side of the cup. In one form, a foil is rolled around the end region of the stem, the rolled foil projecting beyond the end of the stem and thereby forming the cup. Instead of foil, a welded-coil may be used in a similar way to define the cup.
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