| 摘要 |
Cathode venting for electron guns is improved by forming one or more vent holes around the apertures in the triode and any pre-focus lens. This configuration places the vent holes next to the active area of the cathode and provides a line of sight from the cathode to the funnel. If separate alignment holes are used to protect the aperture, one or more vent holes are provided in addition to the alignment holes. The pattern of vent and alignment holes is preferably rotationally symmetric about the aperture so that they do not effect the beam.
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