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Bettin H.,Physikalisch - Technische Bundesanstalt | Fujii K.,NMIJ National Metrology Institute of Japan | Man J.,Australian National Measurement Institute | Mana G.,INRIM - Istituto Nazionale di Ricerca Metrologica | And 2 more authors.
Annalen der Physik | Year: 2013

Fundamental constants link seemingly different fields of physics and seemingly different quantities and measurement units. Consequently, they are of the utmost interest in metrology and it has been planned to redefine the kilogram by fixing the numerical value of the Planck constant. This paper summarises the methods to measure the ratio between the Planck constant and a mass and reviews the determination of the Avogadro constant by counting the atoms in a silicon crystal highly enriched by the 28Si isotope. © 2013 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Andreas B.,Physikalisch - Technische Bundesanstalt | Azuma Y.,NMIJ National Metrology Institute of Japan | Bartl G.,Physikalisch - Technische Bundesanstalt | Becker P.,Physikalisch - Technische Bundesanstalt | And 22 more authors.
Physical Review Letters | Year: 2011

The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the Si28 isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA=6.02214078(18) ×1023mol⊃-1, is the most accurate input datum for a new definition of the kilogram. © 2011 American Physical Society. Source

Arnold T.,Leibniz Institute of Surface Modification | Baumann H.,METAS Federal Office of Metrology | Bettin H.,Physikalisch - Technische Bundesanstalt | Bielsa F.,French National Laboratory of Metrology and Testing | And 9 more authors.
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2014

This paper describes the progress of a joint research project aimed at developing and demonstrating the technologies, based both on the watt balance experiment and the counting of 28Si atoms, necessary to realize the kilogram on the basis of an agreed conventional value of the Planck constant. © 2014 IEEE. Source

Jiang Z.,BIPM Bureau International des Poids et Mesures | Matsakis D.,USNO United States Naval Observatory | Zhang V.,U.S. National Institute of Standards and Technology | Esteban H.,Roa Real Instituto Y Observatorio Of La Armada En San Fernando | And 3 more authors.
Proceedings of the Annual Precise Time and Time Interval Systems and Applications Meeting, PTTI | Year: 2016

Two-Way Satellite Time and Frequency Transfer (TWSTFT) links were first introduced to Coordinated Universal Time (UTC) generation in 1999. These TWSTFT links were calibrated by alignment with the corresponding GPS time links, of which the nominal uncertainty was 5 ns. In the past decade, the primary calibration technique for TWSTFT link calibrations was based on a TWSTFT mobile ground station (MS) with uncertainty at the level of 1 ns. The use of an MS for TWSTFT link calibration is limited by the availability of an MS, a common satellite transponder, transportation, and high cost. For example, due to the lack of a common transponder, a MS cannot be used for a stand-alone calibration of the NIST-PTB link (the link between the National Institue of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB)). Therefore, alternative techniques have been proposed and validated in recent years. Investigations for improving GPS time link calibrations have been performed since 2008. In 2011 this triggered the International Bureau of Weights and Measures (BIPM) to carry out a pilot study on using GPS link calibrations for the UTC TWSTFT time links. The study concluded that a link calibration uncertainty of 1.5 ns is attainable. Based thereon, the 'TWSTFT Calibration Guidelines for the UTC Time Links' recognize the GPS link calibration as an alternative technique for the calibration of TWSTFT links. In this paper, we first outline the new TWSTFT Calibration Guidelines for UTC Time Links (v3.0), which was approved at the 23rd meeting of the Consultative Committee for Time and Frequency (CCTF) Working Group on TWSTFT. It authorizes several techniques, including the GPS link calibration and the Triangle Closure Calibration (TCC). Then we discuss the attainable uncertainty of the GPS calibration. Finally we provide in the Annex an example report of using a GPS calibrator for a typical UTC time link calibration based on the US Naval Observatory (USNO) and PTB, UTC(USNO)-UTC(PTB) TWSTFT link calibration. Here we describe the characteristics of BIPM's Measurement of Total Delay (METODE) Global Navigation Satellite System (GNSS) calibrator, its setup at a UTC laboratory, Lab(k), measurements, and its results. In this calibration, the GPS result differs from that of the TWSTFT MS by 0.9 ns with an uncertainty of 1.5 ns. © 2016 The Institute of Navigation, Inc. Source

Jiang Z.,BIPM Bureau International des Poids et Mesures | Czubla A.,GUM Central Office of Measures | Nawrocki J.,Astrogeodynamic Observatory of Space Research Center | Nogas P.,PikTime AOS and PikTime Systems
Proceedings of the Annual Precise Time and Time Interval Systems and Applications Meeting, PTTI | Year: 2014

One side, the recent developments in TWOTT (Two Way Optical Fiber Time Transfers) technique allows time transfer with a type A and B (uA and uB) combined uncertainty of a hundred ps. The 420 km baseline UTC(AOS)-UTC(PL) between two UTC laboratories AOS and PL is the first self-calibrated time link and operational permanently since 2012. On the other side, in the frame of improving the calibration uncertainty (the type B uncertainty uB) in the UTC time transfers, the BIPM launched in 2011 a pilot project, namely METODE (Measurement of Total Delay). It is composed of a calibration scheme and a travelling standard GNSS calibrator (StdB). The uB is evaluated to be 0.8~1.5 ns for accurate time link calibration. Source

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