| 摘要 |
<p>The tube has three cathodes fixed in a common cup shaped electrode (20) which is aligned with an apertured grid plate (21). The co-planar beams are focused by an electrod (22) and common anode (23). The three cup-shaped parts (24,25,26) of the focusing electrode are disposed coaxially. A centring bush (28) of the common anode has three apertures (31,32,33). Annular field shapers (34) are disposed about the apertures (31,33) for the two outer beams. Two strips of magnetically permeable material are disposed symmetrically about the aperture for the central electron beam. The strips provide coma correction in the direction opposite to that in which coma correction is provided by the annular field shapers (34).</p> |
