| 摘要 |
PURPOSE:To acquire an electron lens with a superhigh vacuum degree, sufficiently bearable to a heating of about 2000 deg.C, by welding the connecting part of an electron beam passage pipe and a yoke. CONSTITUTION:The connecting part of a lower yoke 2 and an electron beam passage pipe 9 is welded with a heliarc welding at the points 21 and 22 respectively through a nonmagnetic material 20, and they are incorporated integrally. The electron beam passage pipe 9 is composed not projecting from the bottom of the lower yoke 2, and the bottom side of the pipe 9 is combined through a lower spacer 27 and a metallic O ring 26. A heater 18 is furnished at the neighboring position of the pipe 9, and another heater 19 is furnished at the bottom side of a spacer 10 for the degasing purpose. Moreover, a cooling pipe 23 is arranged at the upper side and at the lower side of a coil 3 to cool the heating when a current is applied to the coil 3. Therefore, the vacuum condition of the sample chamber can be maintained by the heliarc welding and metallic O rings 12 and 13, and the metallic O rings are bearable sufficiently to the heating of 200 deg.C or more.
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