4137 / Ionenakkumulation at the PTB: EUROPA, DEUTSCHLAND, BRAUNSCHWEIG (BRAUNSCHWEIG, GERMANY), 9.5.2007: Ion accumulation experiment at Physikalisch-Technische Bundesanstalt PTB in Braunschweig, Germany. The experiment is an attempt to redefine SI base unit of mass, the kilogram, by tying it to a fundamental constant: the atomic mass unit. An ion source, bottom left, produces a beam of electrically charged bismuth atoms which are accumulated inside a collector, at right, up to a weighable mass. Ion current and time give the number of accumulated atoms. Knowing the charge of a single ion, the mass of an atom can now be determined. Because the required measurement precision canХt be reached in due time, the experiment will be discontinued. - Marc Steinmetz / VISUM - Keywords: Germany, Physikalisch, Technische, Bundesanstalt, PTB, science, technology, physics, metrology, base, unit, international, system, of, units, SI, metrical, measure, measurement, standard, lab, mass, kilogram, ion, atom, accumulation, beam