The BNM Watt Balance Project

Genevès, G.; Gournay, P.; Gosset, André; Lecollinet, M.; Villar, F.; Pinot, P.; Juncar, P.; Clairon, A.; Landragin, Arnaud; Holleville, David; Santos, F. Pereira Dos; David, J.; Besbes, Mondher; Alvès, Francisco; Chassagne, Luc; Topçu, S.

doi:10.1109/tim.2005.843576

Cited by 112 publications

(81 citation statements)

References 12 publications

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“…This effect is now being investigated, but it is too early to tell how large this error is and if a correction can be applied retrospectively. The two techniques which allow the Planck constant to be determined with the smallest uncertainty (several parts in 10 8 ) are the watt balance and the silicon sphere technique, which has spheres made of isotopically enriched 28 Si. Recent results obtained by these two techniques are shown in figure 6.…”

Section: Overview Of the Available Results For The Planck Constantmentioning

confidence: 99%

“…A new project, based on the experience of the present experiment, has been started with the objective to reach a relative uncertainty close to 1 part in 10 8 . The Laboratoire National de Métrologie et d'Essais in France commenced a watt balance project in the year 2000 and its development started in 2002 [18,28]. Its distinctive feature is that the force comparator is moved together with the coil by a guiding stage.…”

Section: The Existing Watt Balance Experimentsmentioning

confidence: 99%

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The watt balance: determination of the Planck constant and redefinition of the kilogram

Stöck

2011

Phil. Trans. R. Soc. A.

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Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last material artefact to define a base unit of the SI, and it influences several other base units. This situation is no longer acceptable in a time of ever-increasing measurement precision. It is therefore planned to redefine the unit of mass by fixing the numerical value of the Planck constant. At the same time three other base units, the ampere, the kelvin and the mole, will be redefined. As a first step, the kilogram redefinition requires a highly accurate determination of the Planck constant in the present SI system, with a relative uncertainty of the order of 1 part in 10 8 . The most promising experiment for this purpose, and for the future realization of the kilogram, is the watt balance. It compares mechanical and electrical power and makes use of two macroscopic quantum effects, thus creating a relationship between a macroscopic mass and the Planck constant. In this paper, the operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all available experimental determinations of the Planck constant, and it is shown that further investigation is needed before the redefinition of the kilogram can take place. Independent of this requirement, a consensus has been reached on the form that future definitions of the SI base units will take.

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Section: Overview Of the Available Results For The Planck Constantmentioning

confidence: 99%

Section: The Existing Watt Balance Experimentsmentioning

confidence: 99%

The watt balance: determination of the Planck constant and redefinition of the kilogram

Stöck

2011

Phil. Trans. R. Soc. A.

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“…It w i l lal so be m oved cl ose to the LN E watt bal ance experi m ent,w hi ch ai m satm easuri ng thePl anck' sconstant and rede ni ng the ki l ogram . 12 T he authors P.C .and J.L.G .thank D G A for supporti ng thi s work.T he author K .T .T .thanks al so the "Fondati on D anoi se" for i ts support.…”

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confidence: 94%

Compact laser system for atom interferometry

et al. 2006

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C om piled Septem ber 7,2016 W e describe an optical bench in w hich w e lock the relative frequencies or phases of a set of three lasers in order to use them in a cold atom s interferom etry experim ent. A s a new feature, the sam e tw o lasers serve alternately to cool atom s and to realize the atom ic interferom eter. T his requires a fast change of the optical frequencies over a few G H z. T he num ber of required independent laser sources is then only 3, w hich enables the construction of the w hole laser system on a single transportable optical bench. R ecent results obtained w ith this opticalsetup are also presented. c 2016 O pticalSociety ofA m erica O C IS codes: 140. 3320,120.3180,140.3550,120.3930. W i thi n the l ast decades,atom i nterferom eters have devel oped i nto a hi ghl y com peti ti ve tool for preci si on m easurem ents. 1 A tom i c fountai ns used as atom i c cl ocks are the best real i zati on of the ti m e uni t. 2 A tom i nterferom etry al so prom i sessensorsto be hi ghl y sensi ti ve to i nerti alforces. 3{6 T he use of sti m ul ated R am an transiti ons to m ani pul ate the atom i c wave packet has proven to be an e ci entway to obtai n hi gh accuracy devi ces. 5,6 In thi s l etter,we descri be a robust,com pact and versati l e l aser system for atom i nterferom eters usi ng alkal iatom s.Such experi m ents basi cal l y need two di erentopti calfrequenci es,w hose di erence rem ai nscl oseto the hyper ne transi ti on frequency.W hen they are tuned cl ose to the D 2 transi ti ons, they are used to cool and repum p the atom s i n a m agneto-opti cal trap (M O T ). W hen far detuned,and phase l ocked,they are used to i nduce sti m ul ated R am an transi ti onsforthe i nterferometer. 7 Si nce l asers are not used si m ul taneousl y for trappi ng and R am an transi ti ons, we have i m pl em ented a techni que to use the sam e two l asers for both functi ons on ourgravi m eter. 8 Ital l owed usto bui l d the w hol el aser setup on a 60 90 cm 2 opti calbench.O url asersetup i sshow n i n gure 1.A rstl aserL1 i s l ocked on an atom i c transi ti on,usi ng FM -spectroscopy 9 on a saturated absorpti on si gnal .T hi s l aser consti tutes an opti calfrequency reference and i s used i n our experi m ent to detect or push the atom s.A second l aser L2 i s al ternatel y used asrepum per orasm asterR am an l aser. Part ofthe outputs ofL1 and L2 are superi m posed on a fast photodetector (PD 12 ) (H am am atsu G 4176) and the frequency ofthe beatnote i sservo l ocked by usi ng a frequency to vol tage converter.A thi rd l aser L3 i s used al ternatel y as cool i ng or as sl ave R am an l aser.T he frequency di erence between L2 and L3 i s m easured w i th a second opti cal beat note on PD 23 . Fi nal l y, both L2 and L3 beam s are superi m posed and di rected through an acousto-opti calm odul atorei therto a m agneto-opti cal trap or to an atom i c i nterferom eter.B oth frequency l ocks of L2 and L3 use the sam e schem e w hi ch i sshow n i n gure 2.T he opti calbeatnote i ssued from the photode...

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“…As a result, the Planck constant h can be related to the test mass m by comparing the electrical power to the mechanical power in conjunction with the quantum Hall effect [3] and the Josephson effect [4]. Since the proposal in 1975, the watt balance has been widely spread and persuaded at many national metrology institutes (NMIs) [5][6][7][8][9][10][11][12][13]. The detailed principle and recent progress of watt balance experiments at NMIs can be found in several review papers, e.g., [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Field representation of a watt balance magnet by partial profile measurements

Yuan

Zhao

et al. 2015

Metrologia

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Abstract. Permanent magnets with high-permeability yokes have been widely used in watt balances for supplying a robust and strong magnetic field at the coil position. Subjected to the mechanical realization, only several B r (z) (radial magnetic field along the vertical direction) profiles can be measured by coils for field characterization. In this article, we present an algorithm that can construct the global magnetic field of the air gap based on N (N ≥ 1) additional measurements of B r (z) profiles. The proposed algorithm is realized by polynomially estimating the B z (r) function with analysis of basic relations between two magnetic components in air gap, i.e., B r (r, z) and B z (r, z), following the Maxwell's equations. The algorithm, verified by FEM simulations, can characterize the three-dimensional contribution of the magnetic field for a watt balance magnet with acceptable accuracy, which would supply basic field parameters for alignment and misalignment corrections.

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The BNM Watt Balance Project

Cited by 112 publications

References 12 publications

The watt balance: determination of the Planck constant and redefinition of the kilogram

The watt balance: determination of the Planck constant and redefinition of the kilogram

Compact laser system for atom interferometry

Field representation of a watt balance magnet by partial profile measurements

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