| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical window structure that can thin an optical window arranged in a vessel for maintaining such an environment except an ordinary-temperature and ordinary-pressure atmosphere as a high temperature, a low temperature and a vacuum. SOLUTION: A Kovar(R) metal member 12 is thin and has a fold portion 16 between a portion (rim portion 13) held between a body-side flange part 5 and a mounting flange part 6 of the Kovar metal member 12 on one hand, and a portion (top portion 14) where a seal ring 22 is placed on the other hand. The fold portion 16 functions as a stress relaxing portion for relaxing the stress that acts on a quartz plate 21 via the seal ring 22 when the Kovar metal member 12 is held between the body-side flange part 5 and mounting flange part 6 and is fixed to a vacuum vessel 1 (cylindrical portion 3) with the body-side flange part 5 and mounting flange part 6 fastened by means of mounting bolts 7 and nuts 10.
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