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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Helium mass spectrometer ： ウィキペディア英語版 Helium mass spectrometer A helium mass spectrometer is an instrument commonly used to detect and locate small leaks. It was initially developed in the Manhattan Project during World War II to find extremely small leaks in the gas diffusion process of uranium enrichment plants.〔LEAK DETECTION by N. Hilleret of CERN, Geneva, Switzerland. "At the origin of the helium leak detection method was the ”Manhattan Project” and the unprecedented leak-tightness requirements needed by the uranium enrichment plants. The required sensitivity needed for the leak checking led to the choice of a mass spectrometer designed by Dr. A.O.C. Nier tuned on the helium mass. Because of its industrial use, the material choice (originally glass) turned out to be unbearably fragile and after many complaints by the users, a new metallic version was developed and constructed. The sensitivity of the apparatus was in 1946 ~10−7 Pa·m3·s−1 and it increased to ~10−10 Pa·m3·s−1 by 1970. Nowadays the quoted sensitivity of the most sensitive detectors is ~10−13 Pa·m3·s−1, a factor 106 gain within 50 years."〕 It typically uses a vacuum chamber in which a sealed container filled with helium is placed. Helium leaks out of the container, and the rate of the leak is detected by a mass spectrometer. == Detection technique == Helium is used as a tracer because it penetrates small leaks rapidly. Helium has also the property of being non-toxic, chemically inert and present in the atmosphere only in minute quantities (5 ppm). Typically a helium leak detector will be used to measure leaks in the range of 10−5 to 10−12 Pa·m3·s−1. A flow of 10−5 Pa·m3·s−1 is slightly less than 1 ml per minute at standard conditions for temperature and pressure (STP). A flow of 10−13 Pa·m3·s−1 is slightly less than 3 ml per century at STP. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Helium mass spectrometer」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.