| 摘要 |
An electron beam device has a cathode that generates a fan-shaped electron beam. A first focusing lens includes first and second plates on opposed sides of a filament. The edges of the plates closest to a positively charged anode are arcuate, so that as individual electrons are accelerated normal to the edge of the charged plates, the beam increases in length with departure from the filament. A second focusing lens includes third and fourth plates on opposed sides of the first focusing lens. Each of the third and fourth plates has an arcuate edge proximate to the positively charged anode. The plates of the first and second focusing lenses provide focusing in a widthwise direction, while defining the increase in the lengthwise direction. Preferably, the filament is also curved. In the preferred embodiment, the curvature of the plates of the first focusing lens defines a common radius with the plates of the second focusing lens. The electron beam may be projected from the interior of an evacuated tube and may have a length that is not limited by the length of the filament.
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