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The Determination of the Atomic Mass Constant with Ion Accumulation

其他書名	Status and Perspectives
出版	IOP Publishing, 2010
URL	http://books.google.com.hk/books?id=9JP8ZwEACAAJ&hl=&source=gbs_api

註釋An experiment is described for determining the atomic mass constant by accumulating ions from an ion beam up to a weighable mass. It establishes a link between the international prototype of the kilogram, the realization of the associated SI unit and an atomic mass. The items necessary for such an experiment are a high-current ion source, an ion optical system with high transmission, a suitable ion collector and a vacuum balance. With the most recent measurement, a mass of more than 320 mg of bismuth was accumulated and its atomic mass was determined with a relative standard uncertainty of 9.4 x 10-5. Special emphasis is placed on determining the mass loss of the accumulated ions caused through sputter effects in the ion collector. Although work on this experiment at the PTB has now been stopped, we conclude with a number of suggestions that could lead to much smaller relative uncertainty in a future experiment.