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M E Himbert - One of the best experts on this subject based on the ideXlab platform.
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determinations of the Boltzmann Constant
Comptes Rendus Physique, 2018Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E HimbertAbstract:Abstract We review measurements of the Boltzmann Constant, k, the value of which is soon to be fixed at exactly 1.380 649 × 10 − 23 J⋅K−1 for the future revised Systeme international of units. In addition to a description of the theoretical background and of diverse experimental techniques (acoustic thermometry, Johnson noise thermometry, dielectric Constant gas thermometry, and Doppler broadened molecular spectroscopy), the article highlights the decisive role of ab initio calculations of the thermophysical properties of gases, especially helium-4. Perspectives for improvements in thermometry are outlined in the wake of the new definition.
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new measurement of the Boltzmann Constant k by acoustic thermometry of helium 4 gas
Metrologia, 2017Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, C Guianvarch, L. Risegari, C Martin, A Allard, B Marty, P Giuliano A AlboAbstract:The SI unit of temperature will soon be redefined in terms of a fixed value of the Boltzmann Constant k derived from an ensemble of measurements worldwide. We report on a new determination of k using acoustic thermometry of helium-4 gas in a 3-litre volume quasi-spherical resonator. The method is based on the accurate determine of acoustic and microwave resonances to measure the speed of sound at different pressures. We find for the universal gas Constant R = 8.31 44614 (50) Jmol-1K-1. Using the current best available value of the Avogadro Constant, we obtain k = 1.38 064 878(83) ×10^(23) JK-1 with u(k) / k = 0.60 x 10^(-6), where the uncertainty u is one standard uncertainty corresponding to a 68 % confidence level. This value is consistent with previous determinations and with that of the 2014 CODATA adjustment of the fundamental Constants (Mohr et al., Rev. Mod. Phys. 88, 035009 (2016)), within the standard uncertainties. We combined the present values of k and u(k) with earlier values that were measured at LNE. Assuming the maximum possible correlations between the measurements, (klsubgpresentl/subg/〈k〉-1) = 0.071×10lsupg-6l/supg and the combined ur(k) is reduced to 0.56×10lsupg-6l/supg. Assuming minimum correlations, (klsubgpresentl/subg/〈k〉-1) = 0.10×10lsupg-6l/supg and the combined ur(k) is reduced to 0.49×10lsupg-6l/supg.
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determination of the Boltzmann Constant k from the speed of sound in helium gas at the triple point of water
Metrologia, 2015Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, L. Risegari, P Giuliano A AlboAbstract:The Boltzmann Constant k has been determined from a measurement of the speed of sound in helium gas in a quasi-spherical resonator (volume 0.5 l) maintained at a temperature close to the triple point of water (273.16 K). The acoustic velocity c is deduced from measured acoustic resonance frequencies and the dimensions of the quasi-sphere, the latter being obtained via simultaneous microwave resonance. Values of c are extrapolated to the zero pressure limit of ideal gas behaviour. We find J⋅K−1, a result consistent with previous measurements in our group and elsewhere. The value for k, which has a relative standard uncertainty of 1.02 ppm, lies 0.02 ppm below that of the CODATA 2010 adjustment.
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Determination of the Boltzmann Constant with an acoustic quasi-spherical resonator filled with argon
2012Co-Authors: Arnaud Guillou, Laurent Pitre, F Sparasci, D Truong, L. Risegari, M E HimbertAbstract:There is an important interest in the international metrology community for new accurate determinations of the Boltzmann Constant k B , in order to redefine the unit of thermodynamic temperature, the kelvin. The value of the Boltzmann Constant is linked to the speed of sound c in a noble gas. The method described here consists in measuring c inside a quasi-spherical acoustic resonator of inner volume of 0.5 l filled with argon, during an isotherm process at the temperature of the triple point of water (273.16 K) from 0.05 MPa to 0.7 MPa. The determination of k B at LNE-LCM CNAM with this technique allowed us to obtain the value k B = 1.380 647 74 (171) \cdot 10 -23 J \cdot K -1 , i.e. with a relative uncertainty of 1.24 \cdot 10 -6 . In this paper, we particularly focus on the parameters of the experiment which have an effect on the measurement of c with this method (like gas purity, static pressure, etc) and how they were carefully controlled to get the lowest uncertainty on k B up to now.
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determination of the Boltzmann Constant using a quasi spherical acoustic resonator
Philosophical Transactions of the Royal Society A, 2011Co-Authors: L Pitre, F Sparasci, D Truong, Arnaud Guillou, L. Risegari, M E HimbertAbstract:The paper reports a new experiment to determine the value of the Boltzmann Constant, kB = 1.3806477(17) × 10 −23 JK −1 , with a relative standard uncertainty of 1.2 parts in 10 6 . kB was deduced from measurements of the velocity of sound in argon, inside a closed quasispherical cavity at a temperature of the triple point of water. The shape of the cavity was achieved using an extremely accurate diamond turning process. The traceability of temperature measurements was ensured at the highest level of accuracy. The volume of the resonator was calculated from measurements of the resonance frequencies of microwave modes. The molar mass of the gas was determined by chemical and isotopic composition measurements with a mass spectrometer. Within combined uncertainties, our new value of kB is consistent with the 2006 Committee on Data for Science and Technology (CODATA) value: (k new B /kB_CODATA − 1) =− 1.96 × 10 −6 , where the relative uncertainties are ur(k new B ) = 1.2 × 10 −6 and ur(kB_CODATA) = 1.7 × 10 −6 . The new relative uncertainty approaches the target value of 1 × 10 −6 set by the Consultative Committee on Thermometry as a precondition for redefining the unit of the thermodynamic temperature, the kelvin.
L Pitre - One of the best experts on this subject based on the ideXlab platform.
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determinations of the Boltzmann Constant
Comptes Rendus Physique, 2018Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E HimbertAbstract:Abstract We review measurements of the Boltzmann Constant, k, the value of which is soon to be fixed at exactly 1.380 649 × 10 − 23 J⋅K−1 for the future revised Systeme international of units. In addition to a description of the theoretical background and of diverse experimental techniques (acoustic thermometry, Johnson noise thermometry, dielectric Constant gas thermometry, and Doppler broadened molecular spectroscopy), the article highlights the decisive role of ab initio calculations of the thermophysical properties of gases, especially helium-4. Perspectives for improvements in thermometry are outlined in the wake of the new definition.
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determinations of the Boltzmann Constant
Conference on Precision Electromagnetic Measurements, 2018Co-Authors: L PitreAbstract:In the last decade, more than 25 publications have reported a determination of the Boltzmann Constant. Consequently, the International Committee for Weights and Measures (CIPM), at its meeting in October 2017 followed the recommendation of the Consultative Committee for Units (CCU) on the redefinition of the kilogram, ampere, kelvin and mole. For the redefinition of the kelvin the Boltzmann Constant will be fixed with the numerical value 1.380 649 10−23J·K−1.
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new measurement of the Boltzmann Constant k by acoustic thermometry of helium 4 gas
Metrologia, 2017Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, C Guianvarch, L. Risegari, C Martin, A Allard, B Marty, P Giuliano A AlboAbstract:The SI unit of temperature will soon be redefined in terms of a fixed value of the Boltzmann Constant k derived from an ensemble of measurements worldwide. We report on a new determination of k using acoustic thermometry of helium-4 gas in a 3-litre volume quasi-spherical resonator. The method is based on the accurate determine of acoustic and microwave resonances to measure the speed of sound at different pressures. We find for the universal gas Constant R = 8.31 44614 (50) Jmol-1K-1. Using the current best available value of the Avogadro Constant, we obtain k = 1.38 064 878(83) ×10^(23) JK-1 with u(k) / k = 0.60 x 10^(-6), where the uncertainty u is one standard uncertainty corresponding to a 68 % confidence level. This value is consistent with previous determinations and with that of the 2014 CODATA adjustment of the fundamental Constants (Mohr et al., Rev. Mod. Phys. 88, 035009 (2016)), within the standard uncertainties. We combined the present values of k and u(k) with earlier values that were measured at LNE. Assuming the maximum possible correlations between the measurements, (klsubgpresentl/subg/〈k〉-1) = 0.071×10lsupg-6l/supg and the combined ur(k) is reduced to 0.56×10lsupg-6l/supg. Assuming minimum correlations, (klsubgpresentl/subg/〈k〉-1) = 0.10×10lsupg-6l/supg and the combined ur(k) is reduced to 0.49×10lsupg-6l/supg.
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improving acoustic determinations of the Boltzmann Constant with mass spectrometer measurements of the molar mass of argon
Metrologia, 2015Co-Authors: Inseok Yang, L Pitre, Jintao Zhang, Michael R Moldover, Xiaojuan FengAbstract:We determined accurate values of ratios among the average molar masses MAr of 9 argon samples using two completely-independent techniques: (1) mass spectrometry and (2) measured ratios of acoustic resonance frequencies. The two techniques yielded mutually consistent ratios (RMS deviation of 0.16 × 10−6 MAr from the expected correlation) for the 9 samples of highly-purified, commercially-purchased argon with values of MAr spanning a range of 2 × 10−6 MAr. Among the 9 argon samples, two were traceable to recent, accurate, argon-based measurements of the Boltzmann Constant kB using primary acoustic gas thermometers (AGT). Additionally we determined our absolute values of MAr traceable to two, completely-independent, isotopic-reference standards; one standard was prepared gravimetrically at KRISS in 2006; the other standard was isotopically-enriched 40Ar that was used during NIST's 1988 measurement of kB and was sent to NIM for this research. The absolute values of MAr determined using the KRISS standard have the relative standard uncertainty ur(MAr) = 0.70 × 10−6 (Uncertainties here are one standard uncertainty.); they agree with values of MAr determined at NIM using an AGT within the uncertainty of the comparison ur(MAr) = 0.93 × 10−6. If our measurements of MAr are accepted, the difference between two, recent, argon-based, AGT measurements of kB decreases from (2.77 ± 1.43) × 10−6 kB to (0.16 ± 1.28) × 10−6 kB. This decrease enables the calculation of a meaningful, weighted average value of kB with a uncertainty ur(kB) ≈ 0.6 × 10−6.
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determination of the Boltzmann Constant k from the speed of sound in helium gas at the triple point of water
Metrologia, 2015Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, L. Risegari, P Giuliano A AlboAbstract:The Boltzmann Constant k has been determined from a measurement of the speed of sound in helium gas in a quasi-spherical resonator (volume 0.5 l) maintained at a temperature close to the triple point of water (273.16 K). The acoustic velocity c is deduced from measured acoustic resonance frequencies and the dimensions of the quasi-sphere, the latter being obtained via simultaneous microwave resonance. Values of c are extrapolated to the zero pressure limit of ideal gas behaviour. We find J⋅K−1, a result consistent with previous measurements in our group and elsewhere. The value for k, which has a relative standard uncertainty of 1.02 ppm, lies 0.02 ppm below that of the CODATA 2010 adjustment.
Michael R Moldover - One of the best experts on this subject based on the ideXlab platform.
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determination of the Boltzmann Constant with cylindrical acoustic gas thermometry new and previous results combined
Metrologia, 2017Co-Authors: Xiaojuan Feng, Michael R Moldover, Keith A Gillis, J Zhang, James B Mehl, K Zhang, Y N DuanAbstract:We report a new determination of the Boltzmann Constant k B using a cylindrical acoustic gas thermometer. We determined the length of the copper cavity from measurements of its microwave resonance frequencies. This contrasts with our previous work (Zhang et al 2011 Int. J. Thermophys. 32 1297, Lin et al 2013 Metrologia 50 417, Feng et al 2015 Metrologia 52 S343) that determined the length of a different cavity using two-color optical interferometry. In this new study, the half-widths of the acoustic resonances are closer to their theoretical values than in our previous work. Despite significant changes in resonator design and the way in which the cylinder length is determined, the value of k B is substantially unchanged. We combined this result with our four previous results to calculate a global weighted mean of our k B determinations. The calculation follows CODATA's method (Mohr and Taylor 2000 Rev. Mod. Phys. 72 351) for obtaining the weighted mean value of k B that accounts for the correlations among the measured quantities in this work and in our four previous determinations of k B. The weighted mean is 1.380 6484(28) × 10−23 J K−1 with the relative standard uncertainty of 2.0 × 10−6. The corresponding value of the universal gas Constant is 8.314 459(17) J K−1 mol−1 with the relative standard uncertainty of 2.0 × 10−6.
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improving acoustic determinations of the Boltzmann Constant with mass spectrometer measurements of the molar mass of argon
Metrologia, 2015Co-Authors: Inseok Yang, L Pitre, Jintao Zhang, Michael R Moldover, Xiaojuan FengAbstract:We determined accurate values of ratios among the average molar masses MAr of 9 argon samples using two completely-independent techniques: (1) mass spectrometry and (2) measured ratios of acoustic resonance frequencies. The two techniques yielded mutually consistent ratios (RMS deviation of 0.16 × 10−6 MAr from the expected correlation) for the 9 samples of highly-purified, commercially-purchased argon with values of MAr spanning a range of 2 × 10−6 MAr. Among the 9 argon samples, two were traceable to recent, accurate, argon-based measurements of the Boltzmann Constant kB using primary acoustic gas thermometers (AGT). Additionally we determined our absolute values of MAr traceable to two, completely-independent, isotopic-reference standards; one standard was prepared gravimetrically at KRISS in 2006; the other standard was isotopically-enriched 40Ar that was used during NIST's 1988 measurement of kB and was sent to NIM for this research. The absolute values of MAr determined using the KRISS standard have the relative standard uncertainty ur(MAr) = 0.70 × 10−6 (Uncertainties here are one standard uncertainty.); they agree with values of MAr determined at NIM using an AGT within the uncertainty of the comparison ur(MAr) = 0.93 × 10−6. If our measurements of MAr are accepted, the difference between two, recent, argon-based, AGT measurements of kB decreases from (2.77 ± 1.43) × 10−6 kB to (0.16 ± 1.28) × 10−6 kB. This decrease enables the calculation of a meaningful, weighted average value of kB with a uncertainty ur(kB) ≈ 0.6 × 10−6.
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correlations among acoustic measurements of the Boltzmann Constant
Metrologia, 2015Co-Authors: Michael R Moldover, R M Gavioso, David B NewellAbstract:We review correlated uncertainties among the accurate determinations of the Boltzmann Constant that used the techniques of primary acoustic gas thermometry (AGT). We find correlated uncertainty contributions from four sources: (1) the uncertain chemical and isotopic compositions of the test gases that lead to an uncertain average molar mass, (2) measurements of the temperature, (3) measurements of the shape and dimensions of the cavity resonators, and (4) fitting acoustic resonance frequencies as a function of the pressure. Molar-mass-dependent uncertainties are correlated among those measurements that used argon with isotopic abundances determined using an isotopic standard prepared at the Korea Research Institute of Standards and Science in 2006. Correlated, cavity-dependent uncertainties result from using the same cavity for more than one measurement. Small, correlated uncertainties propagate into all the AGT determinations of when acoustic resonance frequencies are fit for using uncertain literature data for the Avogadro Constant and for the thermal conductivity and the higher acoustic virial coefficients of helium or argon.
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test of a virtual cylindrical acoustic resonator for determining the Boltzmann Constant
Metrologia, 2015Co-Authors: Xiaojuan Feng, Michael R Moldover, Keith A Gillis, Jintao ZhangAbstract:We report progress toward determining the Boltzmann Constant kB using the concept of a virtual acoustic resonator, a hypothetical resonator that is mathematically equivalent to a cylindrical cavity with periodic boundary conditions. We derived the virtual resonator by combining the measured frequencies of the longitudinal acoustic modes of two argon-filled, cylindrical cavity resonators in such a way to minimize the effects of the cavities' ends, including transducers and ducts attached to the ends. The cavities had lengths of 80 mm and 160 mm and were operated in their longitudinal (l,0,0) modes. We explored virtual resonators that combine modes of the two resonators that have nearly the same frequencies. The virtual resonator formed from the (2,0,0) mode of the 80 mm resonator combined with the (4,0,0) mode of the 160 mm resonator yielded a value for kB that is, fractionally, only (0.2 ± 1.5) × 10−6 larger than the 2010 CODATA-recommended value of kB. (The estimated uncertainty is one standard uncertainty corresponding to a 68% confidence level.) The same virtual resonator yielded values of the pressure derivatives of the speed of sound c in argon, (∂c2/∂p)T and (∂c2/∂p2)T, that differed from literature values by 1% and 2%, respectively. By comparison, when each cavity was considered separately, the values of kB, (∂c2/∂p)T, and (∂c2/∂p2)T differed from literature values by up to 7 ppm, 10%, and 5%, respectively. However, combining the results from the (3,0,0) or (4,0,0) modes of shorter resonator with the results from the (6,0,0) or (8,0,0) modes of the longer resonator yielded incorrect values of kB that varied from run-to-run. We speculate that these puzzling results originated in an unmodeled coupling, either between the two cavities (that resonated at nearly identical resonance frequencies in the same pressure vessel) or between the cavities and modes of the pressure vessel.
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improved determination of the Boltzmann Constant using a single fixed length cylindrical cavity
Metrologia, 2013Co-Authors: Xiaojuan Feng, Jintao Zhang, Michael R Moldover, Keith A Gillis, Yuanyuan DuanAbstract:We report improvements to our previous (Zhang et al 2011 Int. J. Thermophys. 32 1297) determination of the Boltzmann Constant kB using a single 80 mm long cylindrical cavity. In this work, the shape of the gas-filled resonant cavity is closer to that of a perfect cylinder and the thermometry has been improved. We used two different grades of argon, each with measured relative isotopic abundances, and we used two different methods of supporting the resonator. The measurements with each gas and with each configuration were repeated several times for a total of 14 runs. We improved the analysis of the acoustic data by accounting for certain second-order perturbations to the frequencies from the thermo-viscous boundary layer. The weighted average of the data yielded kB = 1.380 6476 × 10−23 J K−1 with a relative standard uncertainty ur(kB) = 3.7 × 10−6. This result differs, fractionally, by (−0.9 ± 3.7) × 10−6 from the value recommended by CODATA in 2010. In this work, the largest component of the relative uncertainty resulted from inconsistent values of kB determined with the various acoustic modes; it is 2.9 × 10−6. In our previous work, this component was 7.6 × 10−6.
F Sparasci - One of the best experts on this subject based on the ideXlab platform.
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determinations of the Boltzmann Constant
Comptes Rendus Physique, 2018Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E HimbertAbstract:Abstract We review measurements of the Boltzmann Constant, k, the value of which is soon to be fixed at exactly 1.380 649 × 10 − 23 J⋅K−1 for the future revised Systeme international of units. In addition to a description of the theoretical background and of diverse experimental techniques (acoustic thermometry, Johnson noise thermometry, dielectric Constant gas thermometry, and Doppler broadened molecular spectroscopy), the article highlights the decisive role of ab initio calculations of the thermophysical properties of gases, especially helium-4. Perspectives for improvements in thermometry are outlined in the wake of the new definition.
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new measurement of the Boltzmann Constant k by acoustic thermometry of helium 4 gas
Metrologia, 2017Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, C Guianvarch, L. Risegari, C Martin, A Allard, B Marty, P Giuliano A AlboAbstract:The SI unit of temperature will soon be redefined in terms of a fixed value of the Boltzmann Constant k derived from an ensemble of measurements worldwide. We report on a new determination of k using acoustic thermometry of helium-4 gas in a 3-litre volume quasi-spherical resonator. The method is based on the accurate determine of acoustic and microwave resonances to measure the speed of sound at different pressures. We find for the universal gas Constant R = 8.31 44614 (50) Jmol-1K-1. Using the current best available value of the Avogadro Constant, we obtain k = 1.38 064 878(83) ×10^(23) JK-1 with u(k) / k = 0.60 x 10^(-6), where the uncertainty u is one standard uncertainty corresponding to a 68 % confidence level. This value is consistent with previous determinations and with that of the 2014 CODATA adjustment of the fundamental Constants (Mohr et al., Rev. Mod. Phys. 88, 035009 (2016)), within the standard uncertainties. We combined the present values of k and u(k) with earlier values that were measured at LNE. Assuming the maximum possible correlations between the measurements, (klsubgpresentl/subg/〈k〉-1) = 0.071×10lsupg-6l/supg and the combined ur(k) is reduced to 0.56×10lsupg-6l/supg. Assuming minimum correlations, (klsubgpresentl/subg/〈k〉-1) = 0.10×10lsupg-6l/supg and the combined ur(k) is reduced to 0.49×10lsupg-6l/supg.
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determination of the Boltzmann Constant k from the speed of sound in helium gas at the triple point of water
Metrologia, 2015Co-Authors: L Pitre, F Sparasci, M D Plimmer, M E Himbert, L. Risegari, P Giuliano A AlboAbstract:The Boltzmann Constant k has been determined from a measurement of the speed of sound in helium gas in a quasi-spherical resonator (volume 0.5 l) maintained at a temperature close to the triple point of water (273.16 K). The acoustic velocity c is deduced from measured acoustic resonance frequencies and the dimensions of the quasi-sphere, the latter being obtained via simultaneous microwave resonance. Values of c are extrapolated to the zero pressure limit of ideal gas behaviour. We find J⋅K−1, a result consistent with previous measurements in our group and elsewhere. The value for k, which has a relative standard uncertainty of 1.02 ppm, lies 0.02 ppm below that of the CODATA 2010 adjustment.
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the imeraplus joint research project for determinations of the Boltzmann Constant
TEMPERATURE: ITS MEASUREMENT AND CONTROL IN SCIENCE AND INDUSTRY VOLUME 8: Proceedings of the Ninth International Temperature Symposium, 2013Co-Authors: Johann Fischer, L Pitre, B Fellmuth, Christof Gaiser, T Zandt, S Briaudeau, F Sparasci, D Truong, Y Hermier, R M GaviosoAbstract:To provide new determinations of the Boltzmann Constant, k, which has been asked for by the International Committee for Weights and Measures concerning preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole, an iMERAPlus joint research project has coordinated the European activities in this field. In this major European research project the Boltzmann Constant has been determined by various methods to support the new definition of the kelvin. The final results of the project are reviewed in this paper. Determinations of the Boltzmann Constant k were achieved within the project by all three envisaged methods: acoustic gas thermometry, Doppler broadening technique, and dielectric Constant gas thermometry. The results were exploited by the interdisciplinary Committee on Data for Science and Technology (CODATA) in their 2010 adjustment of recommended values for fundamental Constants. As a result, the CODATA group recommended a value for k with a relative standard uncertainty about a factor of two smaller than the previous u(k)/k of 1.7×10−6.To provide new determinations of the Boltzmann Constant, k, which has been asked for by the International Committee for Weights and Measures concerning preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole, an iMERAPlus joint research project has coordinated the European activities in this field. In this major European research project the Boltzmann Constant has been determined by various methods to support the new definition of the kelvin. The final results of the project are reviewed in this paper. Determinations of the Boltzmann Constant k were achieved within the project by all three envisaged methods: acoustic gas thermometry, Doppler broadening technique, and dielectric Constant gas thermometry. The results were exploited by the interdisciplinary Committee on Data for Science and Technology (CODATA) in their 2010 adjustment of recommended values for fundamental Constants. As a result, the CODATA group recommended a value for k with a relative standard uncerta...
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Determination of the Boltzmann Constant with an acoustic quasi-spherical resonator filled with argon
2012Co-Authors: Arnaud Guillou, Laurent Pitre, F Sparasci, D Truong, L. Risegari, M E HimbertAbstract:There is an important interest in the international metrology community for new accurate determinations of the Boltzmann Constant k B , in order to redefine the unit of thermodynamic temperature, the kelvin. The value of the Boltzmann Constant is linked to the speed of sound c in a noble gas. The method described here consists in measuring c inside a quasi-spherical acoustic resonator of inner volume of 0.5 l filled with argon, during an isotherm process at the temperature of the triple point of water (273.16 K) from 0.05 MPa to 0.7 MPa. The determination of k B at LNE-LCM CNAM with this technique allowed us to obtain the value k B = 1.380 647 74 (171) \cdot 10 -23 J \cdot K -1 , i.e. with a relative uncertainty of 1.24 \cdot 10 -6 . In this paper, we particularly focus on the parameters of the experiment which have an effect on the measurement of c with this method (like gas purity, static pressure, etc) and how they were carefully controlled to get the lowest uncertainty on k B up to now.
Christophe Daussy - One of the best experts on this subject based on the ideXlab platform.
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Experimental determination of Boltzmann's Constant Measurement of the Boltzmann Constant by the Doppler broadening technique at a 3.8 × 10 −5 accuracy level
2020Co-Authors: Khelifa Djerroud, S Briaudeau, O Lopez, Cyril Lemarchand, Benoit Darquie, Christian Chardonnet, Christophe Daussy, Alexandre Gauguet, A. Amy-klein, Christian J BordeAbstract:In this article, we describe an experiment performed at the Laboratoire de physique des lasers and dedicated to an optical measurement of the Boltzmann Constant kB. With the proposed innovative technique, determining kB comes down to an ordinary frequency measurement. The method consists in measuring as accurately as possible the Doppler absorption profile of a rovibrational line of ammonia in thermal equilibrium. This profile is related to the Maxwell–Boltzmann molecular velocity distribution along the laser beam. A fit of the absorption line shape leads to a determination of the Doppler width proportional to √ kBT and thus to a determination of the Boltzmann Constant. The laser source is an ultra-stable CO2 laser with a wavelength λ ≈ 10 µm. The absorption cell is placed in a thermostat, keeping the temperature at 273.15 K within 1.4 mK. We were able to measure kB with a relative uncertainty as small as 3.8 × 10 −5 , which represents an improvement of an order of magnitude for an integration time
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absorption line shape recovery beyond the detection bandwidth limit application to the precision spectroscopic measurement of the Boltzmann Constant
Physical Review A, 2014Co-Authors: Francois Rohart, S Mejri, Benoit Darquie, Christian Chardonnet, Eugenio Fasci, A Castrillo, L Gianfrani, Sean Tokunaga, Hemanth Dinesan, Christophe DaussyAbstract:A theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate central frequencies and other spectroscopic parameters. This reveals sources of systematic effects most probably underestimated so far potentially affecting spectroscopic measurements. This may impact many fields of research, from atmospheric and interstellar physics to precision spectroscopic measurements devoted to metrological applications, tests of quantum electrodynamics or other fundamental laws of nature. Our theoretical model is validated by linear absorption experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy in two distinct spectral regions, near- and mid-infrared. Possible means of recovering original line shape parameters or experimental conditions under which the detection bandwidth has a negligible impact, given a targeted accuracy, are proposed. Particular emphasis is put on the detection bandwidth adjustments required to use such high-quality molecular spectra for a spectroscopic determination of the Boltzmann Constant at the 1 ppm level of accuracy.
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absorption line shape recovery beyond the detection bandwidth limit application to the Boltzmann Constant determination
2014Co-Authors: Francois Rohart, S Mejri, Benoit Darquie, Christian Chardonnet, Eugenio Fasci, A Castrillo, L Gianfrani, Sean Tokunaga, Hemanth Dinesan, Christophe DaussyAbstract:A theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate line parameters. The theoretical model is validated by experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy. Particular emphasis is put on the detection bandwidth adjustments required to perform a spectroscopic determination of the Boltzmann Constant at the 1 ppm level of accuracy.
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speed dependent effects in nh 3 self broadened spectra towards the determination of the Boltzmann Constant
Physical Review A, 2012Co-Authors: M Triki, Cyril Lemarchand, Benoit Darquie, Christian Chardonnet, V Roncin, Christophe DaussyAbstract:In this paper we present an accurate analysis of the shape of an isolated rovibrational ammonia line from the strong nu2 band around 10 $\mu$m, recorded by laser absorption spectroscopy. Experimental spectra obtained under controlled temperature and pressure, are confronted to various models that take into account Dicke narrowing or speed-dependent effects. Our results show clear evidence for speed-dependent broadening and shifting, which had never been demonstrated so far in NH3. Accurate lineshape parameters of the nu2 saQ(6,3) line are obtained. Our current project aiming at measuring the Boltzmann Constant, kB, by laser spectroscopy will straight away benefit from such knowledge. We anticipate that a first optical determination of kB with a competitive uncertainty of a few ppm is now reachable.
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progress towards an accurate determination of the Boltzmann Constant by doppler spectroscopy
New Journal of Physics, 2011Co-Authors: Cyril Lemarchand, M Triki, Benoit Darquie, Christian Chardonnet, Christian J Borde, Christophe DaussyAbstract:In this paper, we present the significant progress made by an experiment dedicated to the determination of the Boltzmann Constant, kB, by accurately measuring the Doppler absorption profile of a line in ammonia gas at thermal equilibrium. This optical method based on the first principles of statistical mechanics is an alternative to the acoustical method, which has led to the unique determination of kB published by the Committee on Data for Science and Technology with a relative accuracy of 1.7?10?6. We report on the first measurement of the Boltzmann Constant carried out by using laser spectroscopy with a statistical uncertainty below 10?p.p.m., more specifically 6.4?p.p.m. This progress results from the improvement in the detection method and in the statistical treatment of the data. In addition, we have recorded the hyperfine structure of the probed ?2 saQ(6,3) rovibrational line of ammonia by saturation spectroscopy and thus determine very precisely the induced 4.36 (2)?p.p.m. broadening of the absorption linewidth. We also show that in our well-chosen experimental conditions, saturation effects have negligible impact on the linewidth. Finally, we suggest directions for future work to achieve an absolute determination of kB with an accuracy of a few p.p.m.
