| 摘要 |
PURPOSE: An electron gun is provided to achieve improved focus characteristics of electron beam and sensitivity of velocity modulator by removing the asymmetry of electric fields in the fourth electrode. CONSTITUTION: An electron gun(2) comprises a single cathode(4) for emitting thermal electrons; a first electrode(6) and a second electrode(8) cooperating with the cathode so as to constitute a triode unit; a third electrode(10) disposed next to the second electrode; a fourth electrode disposed next to the third electrode, and which includes a first focus electrode(12A) and a second focus electrode(12B) arranged with a VM gap(G) formed between the first and second focus electrodes, and an electric field cutoff portion(14) arranged at ends of the first and second focus electrodes; a fifth electrode(16) disposed next to the fourth electrode and applied with an anode voltage; a connector for electrically connecting the fourth and fifth electrodes; and a pair of supports for alignment of the electrodes.
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