| 摘要 |
Since a peripheral part of the sapphire plate 2 is airtightly thermally crimped to an end face (window peripheral part) of a kovar metal tube 1 A surrounding a light entering window via a seal ring 7 made of aluminum, a lattice defect is prevented from occurring on the sapphire plate 2 due to diffusion of impurities on the sapphire plate 2 . As a result, the generation of phosphorescence or fluorescence from the sapphire plate 2 is prevented in detecting an ultraviolet ray, and dark noise is reduced.
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