| 摘要 |
The invention relates to an electron gun (100) for use in a cathode ray tube. The electron gun (100) has an electron source (10), a body (20) with a transmission cavity (25) of which the wall (28) is at least partly coated with an electrical insulator for the emission of secondary electrons, and an electrode (30) for applying a first electric field between the entrance (26) and the exit (27) of the cavity. The electron gun is characterized in that it comprises means for preventing the travelling of positive ions, which are formed by collisions of electrons that have exited from the cavity (25), in reverse direction along the same path as the electrons and colliding with the module (20). Such collisions can damage the cavity exit (27) or the electrical insulator on the wall (28). This is undesirable because the current density of the electron beam (101) exiting from the cavity (25) will deteriorate. This effect is prevented through the application of the deflection means according to the invention.
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