A New Magnet Design for the METAS Watt Balance

Eichenberger, A.; Butty, J.; Jeanneret, B.; Jeckelmann, B.; Joyet, A.; Krebs, T.; Richard, Philippe

doi:10.1109/cpem.2004.305418

Cited by 6 publications

(5 citation statements)

References 4 publications

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“…The specification for this regrinding was to add a taper such that the gap is nominally 3.000 cm at the top to 3.008 cm at the bottom. Varying the gap is a known technique to engineer a desired field profile [9,10]. Fig.…”

Section: Initial Assembly and Attempts To Shim The Fieldmentioning

confidence: 99%

Construction, Measurement, Shimming, and Performance of the NIST-4 Magnet System

Seifert

Panna

et al. 2014

IEEE Trans. Instrum. Meas.

112

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The magnet system is one of the key elements of a watt balance. For the new watt balance currently under construction at the National Institute of Standards and Technology, a permanent magnet system was chosen. We describe the detailed construction of the magnet system, first measurements of the field profile, and shimming techniques that were used to achieve a flat field profile. The relative change of the radial magnetic flux density is less than 10 −4 over a range of 5 cm. We further characterize the most important aspects of the magnet and give order of magnitude estimates for several systematic effects that originate from the magnet system.

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Section: Initial Assembly and Attempts To Shim The Fieldmentioning

confidence: 99%

Construction, Measurement, Shimming, and Performance of the NIST-4 Magnet System

Seifert

Panna

et al. 2014

IEEE Trans. Instrum. Meas.

112

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“…A better magnet was designed and installed by 2004, shown in figure 22(b) from [148]. The magnet's core material was moved farther from the center and thus, farther from the coil.…”

Section: The Metas Swiss Balance-designed For Compactnessmentioning

confidence: 99%

History and progress on accurate measurements of the Planck constant

Steiner

2012

Rep. Prog. Phys.

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The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Sin...

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“…Later, the METAS Mark I magnet system was redesigned to address the hysteresis issue. As shown in figure 7(b), the PMs (SmCo) were removed from the center and inserted into respectively the upper and lower ends of the circuit [47]. In this new design, the PMs act also as spacers to cut the previously closed yoke loop.…”

Section: Flat Permanent Magnet Systemmentioning

confidence: 99%

The irony of the magnet system for Kibble balances—a review

Schlamminger

2022

Metrologia

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The magnet system is an essential component of the Kibble balance, a device that is used to realize the unit of mass. It is the source of the magnetic flux, and its importance is captured in the geometric factor $Bl$. Ironically, the $Bl$ factor cancels out and does not appear in the final Kibble equation. Nevertheless, care must be taken to design and build the magnet system because the cancellation is perfect only if the $Bl$ is the same in both modes: the weighing and velocity mode. This review provides the knowledge necessary to build a magnetic circuit for the Kibble balance. In addition, this article discusses the design considerations, parameter optimizations, practical adjustments to the finished product, and an assessment of systematic uncertainties associated with the magnet system.

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A New Magnet Design for the METAS Watt Balance

Cited by 6 publications

References 4 publications

Construction, Measurement, Shimming, and Performance of the NIST-4 Magnet System

Construction, Measurement, Shimming, and Performance of the NIST-4 Magnet System

History and progress on accurate measurements of the Planck constant

The irony of the magnet system for Kibble balances—a review

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