Definition Of Kilogram Research Articles

External Magnetic Field Measurements in UME Kibble Balance

The new definition of kilogram in terms of the fixed value of Planck constant ensures the long-term stability of SI mass unit and enables traceability from more than one source. Kibble balance experiments offer an effective primary realization method for the new definition of kilogram. Kibble Balance apparatus operating at National Metrology Institute of Turkey is designed with a stationary coil and an oscillating magnet. In contradistinction to traditional moving coil Kibble balance experiments, external magnetic field brings an asymmetry between the Ampere’s law of force and the Faraday’s law of induction in moving magnet experiments. In this paper, we develop a method based on the external magnetic flux density difference measurements in vertical direction to take into account the effect of the external magnetic field on the realization of kilogram. The proposed model in this approach fits well with the data such that the kilogram realization requirement is met within the accuracy of the measuring instrument.

High precision determination of the Planck constant by modern photoemission spectroscopy

The Planck constant, with its mathematical symbol h, is a fundamental constant in quantum mechanics that is associated with the quantization of light and matter. It is also of fundamental importance to metrology, such as the definition of ohm and volt and the latest definition of kilogram. One of the first measurements to determine the Planck constant is based on the photoelectric effect; however, the values thus obtained so far have exhibited a large uncertainty. The accepted value of the Planck constant, 6.626 070 15 × 10-34 J s, is obtained from one of the most precise methods, the Kibble balance, which involves the quantum Hall effect, the Josephson effect, and the use of the international prototype of the kilogram or its copies. Here, we present a precise determination of the Planck constant by modern photoemission spectroscopy technique. Through the direct use of Einstein's photoelectric equation, the Planck constant is determined by accurately measuring the energy position of the gold Fermi level using light sources with various photon wavelengths. The precision of the Planck constant as measured in this work, 6.626 10(13) × 10-34 J s, is improved by four to five orders of magnitude from the previous photoelectric effect measurements. We propose that this direct method of photoemission spectroscopy has potential to further increase its measurement precision of the Planck constant to be comparable to the most accurate methods available at present.

Why have international metrology Heads called the New SI “fundamentally better” and could it be even better?

In November 2018, the 26th General Conference on Weights and Measures (CGPM) adopted the changes to the In­ternational System of Units (SI), which got the conventional name “the New SI”. These changes came into force on May 20, 2019, on World Metrology Day. International metrology Heads have called it “fundamentally better”. This article is devoted to discussing such an assessment.The article shows that the whole history of metrology development is the search for optimal physical quantities and units of measurement, as well as such stable phenomena and objects of nature that could be the basis for the reproduction of these units and creation of the measurement standards.It took almost 150 years of searching and taking certain steps before the ideas of scientists were put into practice in the New SI — quantum SI. The base of this system is fundamental physical constants (FPCs) — standards of nature, micro objects have become the carriers of the sizes of units, and methods of their connection with the macrocosm — quantum phenomena and effects.The article shows that in all measurement fields where quantum methods and definitions of units were implemented through FPCs, there was a significant — by 2–3 orders of magnitude — increase in the accuracy and reliability of the realization of units.The 26th CGPM made the final decision on the new definitions of the base units. The article contains an excerpt from Resolution 1 of the 26th CGPM 2018, as well as its Annexes.An analysis of new definitions of the base units is given. It is shown that the new definitions of second, metre and candela are relevant to their definitions in the previous version of SI and differ only in wording. The definition of kilogram is fundamentally new and is based on the fixed value of Planck’s constant. Significantly new definition is also obtained by the unit of electric current. This means the recognition of quantum methods in electrical measurements, which have in practice confirmed their outstanding metrological capabilities. Definition of kelvin through the Boltzmann constant, experts believe, will contribute to the development of primary thermometry and thermodynamics as a whole.The article also highlights the fundamental advantages of the New SI and outlines the prospective tasks of metrology.

Determination of the Avogadro constant – A contribution to the new definition of the mass unit kilogram

An improved attempt of several national metrology institutes to replace the present definition of the kilogram with the mass of a certain number of 12C atoms is described. This requires the determination of the Avogadro constant, NA, via the silicon route with a relative uncertainty better than 2 ⋅ 10-8. Previously, the limiting factor is the measurement of the average molar mass. Consequently, a world-wide collaboration has been set up, to produce, approximately, 5 kg of 28Si single-crystal with an enrichment factor greater than 99.985% to be used for an improved determination of NA. The first successful tests of all technological steps (enrichment of SiF4, purification and synthesis of silane, deposition of polycrystalline 28Si, single crystal growth) for the production of high-purity 28Si are described.