| 摘要 |
The rotationally-symmetric electron gun of a cathode-ray tube device comprises successively a cathode, a disk-shaped control grid provided with a central control, grid aperture and a disk-shaped anode grid provided with a central circular-cylindrical anode grid aperture. The cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface. The control grid aperture, on the side of the anode grid, has a circular-cylindrical part and, on the side of the cathode, has a conical part which narrows towards the circular-cylindrical part, the wall of which encloses substantially an angle of 45 DEG with the axis of the electron gun. The diameter of the said first conductive circular cylinder and the diameter of the said circular-cylindrical part are substantially six times as large as the diameter of the emitting surface, while the diameter of the anode grid aperture is substantially four times as large, the length of the said second conductive cylinder is substantially twice as large, the distance between the emitting surface and the said circular-cylindrical part is substantially equally large, the axial length of the said conical part is at least equally large and the distance between the control grid and the anode grid is substantially one and a half times as large as the diameter of the emitting surface. The control grid is kept at a negative potential relative to the cathode. The anode is kept at a positive potential which is substantially four and a half times as large, relative to the cathode, while the space on the side of the anode grid remote from the control grid is kept substantially field-free.
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