| 摘要 |
PURPOSE:To ease an oxide treatment of a supporting frame as well as to prevent an unnecessary deformation of an optical window by forming the supporting frame with iron or an alloy including iron, and making the supporting frame and the optical window vacuum-airtightly jointed with the optical window hardly destroyed in an optical state. CONSTITUTION:Each supporting frame 5 and 10 is made of a metal, for instance, iron or alloy including iron, and each supporting frame 5 and 10, an input window 1, and an output window 3 are jointed vacuum-airtightly with each window hardly destroyed in an optical state, Furthermore, a ring supporting frame 5 is airtightly jointed by indium 7 to an end of a tubular vessel body 8 made of ceramics, a ring supporting plate 11 is fixed to the other end of the vessel body 8, and the supporting frame 10 is airtightly jointed to the supporting plate 11 by an arc welding 9. And the vicinity of each effective surface of the input window 1 and the output window 3 is projected to the vacuum side than each supporting frame 5 anc 10, an outside diameter of each effective surface is set to 0.5 mm or above smaller than an inside diameter of each supporting frame 5 and 10, and a gap G is provided. This enables an acid treatment to be available in an elimination of a metal oxide film, and a deformation of an output window eliminated.
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