| 摘要 |
An electron beam gun comprising a beam generator (4), an acceleration chamber (7) and a beam-guide chamber (10). The beam-guide chamber is formed by a jacket tube (19) and a beam-guide tube (18), which extends to the work chamber (1) and is surrounded by a focusing lens (15) and a deflecting device (17). For the purpose of readily adapting the equipment to suit various objective distances and for making cleaning and inspection easier, the jacket tube (19) takes the form of a hollow cylinder and is secured between two connecting flanges (20, 21) in a manner whereby it can be replaced. The upper connecting flange (20) carries a centering flange (28), on which the beam-guide tube is suspended, a shut-off valve (11) being optionally provided between the centering flange and the beam-guide tube. The lower connecting flange (21) surrounds a vacuum-connecting flange (34) in which is fitted the lower end of the beam-guide tube (18). Thus, when the beam generator (4) is removed, the beam-guide tube (18) can be extracted from the focusing lens (15) and from the deflector unit (17) through the acceleration chamber (7), together with the centering flange (28). The boundary between the vacuum and the atmosphere lies in the zone of the beam-guide tube (18) and of its various sealing elements.
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