| 摘要 |
A triode of electron gun used for cathode-ray tube includes a spherical cathode(1) and the first grid(2) with auxiliary V-type concaved grid(2b). When the cathode is heated by the heater, thermal electrons are emitted and distributed on spherical cathode as an electron-cloud of space charge, and then the electric field(5) resulted from the first grid with auxiliary grid is distributed along the spherical surface of the cathode uniformly, and the homogeneity of the emission density is provided. A required perveance is P=(Ib/ (Vb)3/2) where IB is beam-current, VB is the second grid voltage. And the curvature of spherical cathode is &thgr;=f(d/Rc).
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