Use of GPS ASHTECH Z12T receivers for accurate time and frequency comparisons

The GPS phase measurements described in this paper were obtained using two similar multichannel GPS ASHTECH Z12T receivers belonging to the Bureau International des Poids et Mesures, BIPM, and the Laboratoire Primaire du Temps et des Frequences, BNM-LPTF. These receivers are based on the conventional geodetic ASHTECH Z12 unit, which has been modified to meet the stability requirements of time and frequency comparisons. Comparison of the two receivers operated side by side in different antenna configurations shows typical short-term noise of 1.1 to 3.5 ps. Longer term variations indicate a temperature sensitivity in the equipment, which limits the performance of the GPS phase method. One of the receivers was successfully operated using a temperature-stabilized antenna TSA from 3S Navigation, and the ASHTECH antenna, which feeds the second receiver, was placed in a home-built oven maintained at a constant temperature. These precautions made it possible to reduce a number of systematic effects. A separate study of frequency comparison was carried out between two hydrogen-masers located at the BNM-LPTF (Paris, France) and the PTB (Braunschweig, Germany) using receivers similar to ASHTECH Z12T receivers. The relative frequency stability obtained was about 3.3x10(-15) for an average time of 15 000 s, an interesting result comparable with the outstanding performance of new ultrastable frequency standards.     

International comparison of power measurements at 33 GHz(GT-RF/92-4)

A measurement comparison of effective efficiency has been carried out between eight national metrology laboratories at 33 GHz in rectangular waveguide IEC R320. Two waveguide thermistor mounts were measured. The following national laboratories participated: BNM-LCIE (France), NIST (U.S.), NRC (Canada), KRISS (Korea), CSIRO (Australia), PTB (Germany), NMi VSL (The Netherlands), and NPL (U.K.). The Bureau National de Metrologie-Laboratoire Central des Industries Electriques (France) acted as the pilot laboratory for the comparison. Excellent harmony is observed between results given by the participants, especially for the item LCIE-92021     

International comparisons of the CCPR-S1 units of spectral radiance at wavelengths of 220–2500 nm

The Consultative Committee for Photometry and Radiometry (CCPR) has organized international comparisons of the CCPR-S1 units of spectral radiance at wavelengths of 220–2500 nm with participation by the BNM-INM (France), NIST (USA), NRC (Canada), PTB (Germany), and VNIIOFI (Russia), with the latter as the pilot laboratory. The methods and equipment for these measurements, as well as the results of the comparisons, are discussed. The comparisons showed that the discrepancies between the spectral radiance scales were basically within ±1.5%. This discrepancy decreases to ±1.0% if the data from highly unstable transfer standards are eliminated from the analysis.     

Comparison of the NIST and NPL Air Kerma Standards Used for X-Ray Measurements Between 10 kV and 80 kV

A direct comparison was made between the air kerma primary standards used for the measurements of low-energy x rays at the National Institute of Standards and Technology (NIST) and the National Physical Laboratory (NPL). The comparison was conducted at the NPL using NPL reference radiation qualities between 10 kV and 80 kV. The results show the primary air-kerma standards to agree within 0.6 % of their values for beam qualities up to 80 kV.     

Comparison of the NIST and PTB Air-Kerma Standards for Low-Energy X-Rays

A comparison has been made of the air-kerma standards for low-energy x rays at the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). The comparison involved a series of measurements at the PTB and the NIST using the air-kerma standards and two NIST reference-class transfer ionization chamber standards. Results are presented for the reference radiation beam qualities in the range from 25 kV to 50 kV for low energy x rays, including the techniques used for mammography dose traceability. The tungsten generated reference radiation qualities, between 25 kV and 50 kV used for this comparison, are new to NIST; therefore this comparison will serve as the preliminary comparison for NIST and a verification of the primary standard correction factors. The mammography comparison will repeat two previously unpublished comparisons between PTB and NIST. The results show the standards to be in reasonable agreement within the standard uncertainty of the comparison of about 0.4 %.     

Volumetric Digital Image Correlation Applied to X-ray Microtomography Images from Triaxial Compression Tests on Argillaceous Rock

Abstract:  A set of triaxial compression tests on specimens of argillaceous rock were performed under tomographic monitoring at the European Synchrotron Radiation Facility in Grenoble, France, using an original experimental set-up developed at Laboratoire 3S , Grenoble. Complete 3D images of the specimens were recorded throughout each test using X-ray microtomography. Such images were subsequently analysed using a Volumetric Digital Image Correlation software developed at the Laboratoire de Mécanique des Solides in Palaiseau, France. Full-field incremental strain measurements were obtained, which allow to detect the onset of shear strain localisation and to characterise its development in a 3D complex pattern. Volumetric Digital Image Correlation revealed patterns which could not be directly observed from the original tomographic images, because the deformation process in the zones of localised deformation was essentially isochoric (i.e. without volumetric strain), hence not associated to density changes.     

Comparison of four QHR systems within one month using a temperatureand pressure stabilized 100-Ω resistor

We have carried out a resistance comparison of four QHR systems using a 100-Ω resistor in a temperature-controlled and hermetically sealed enclosure, the comparison was performed in November and December 1998, the participants were Bureau International des Poids et Mesures (BIPM), Bureau National de Metrology-Laboratoire Central des Industries Electroniques (BNM-LCIE) France, Physikalisch-Technische Bundesanstalt (PTB) Germany, and Valtion Teknillinen Tutkimuskeskus (VTT Automation) Finland, acting as a pilot laboratory. The comparison results agree within 3 parts in 10⁹ with a relative combined standard uncertainty of ±1×10^-8     

Intercomparison of the Realizations of the ITS-90 from 83.8058 K to 692.677 K among European NMIs

The EUROMET.T-K3 comparison is the regional extension of CCT-K3. The comparison involved the six European national metrology institutes (NMIs) previously involved in CCT-K3 (LNE-INM/CNAM, SMU, INRiM, NMi-VSL, NPL, PTB) and 18 additional European national laboratories. The comparison was divided into five different loops, each coordinated by a co-pilot chosen from the laboratories having participated in the CCT-K3 comparison. LNE-INM/CNAM played the role of pilot in linking the five loops. In each loop, an artifact in the form of a standard platinum resistance thermometer (SPRT, 25 Ω) was circulated among the participating laboratories. To have sufficient information about the possible drift of the SPRTs, the co-pilots performed a calibration over the full temperature range at the beginning and at the end of the loop. A EUROMET reference value (ERV), taking into account the whole comparison, was defined, and the differences (T _Lab − T _ERV) were calculated with the associated uncertainties. The method for establishing the link between the participants in CCT-K3 and in EUROMET.T-K3 is described. Institut National de Métrologie (BNM-INM/CNAM at the time of the comparison, LNE-INM/CNAM since 1 January 2005), Paris, France.     

Water distribution in beams damaged by alkali-silica reaction: Global weighing and local gammadensitometry

Within the framework of an experimental programme developed by the Laboratoire Central des Ponts et Chaussées (LCPC) and électricité de France (EDF), in the aim of increasing knowledge on Alkali-Silica Reaction (ASR) and understanding the effect of water on ASR development in structures, two techniques have been designed to measure water content vs. time in large-scale concrete specimens. Global weighing variations are monitored on six 900 kg beams; and the, gammadensitometry measurement allows evaluating water content profiles in the beams. These two complementary measurements serve to validate water content models and correlate the moisture gradient with measured deformations The measurement principle, execution, and qualification are first described. The accuracy of the weighing device is thus evaluated at 10 g, and the uncertainty of the gammadensitometry method is close to 0.4% of relative mass. The paper then presents the results of one-year monitoring conducted on one of these beams and proves the consistency of these methods. At last, it is shown that the square root of time kinetics allows a good representation of the global mass variations of the beams and that the drying depth reaches between 80 and 100 mm after one year exposure.

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Résumé Dans le cadre d'une campagne d'expérimentation cofinancée par le LCPC (Laboratoire Central des Pont et Chaussées) et EDF (électricité de France), destinée à approfondir les connaissances sur l'alcali-réaction et en particulier les conséquences de la teneur en eau libre sur le développment de cette pathologie dans des structures, deux techniques de suivi de l'évolution hydrique de ce type de corps d'épreuve de grandes dimensions ont été mises au point. La première permet de suivre la masse de six poutres d'environ 900 kg avec une précision de l'ordre de la dizaine de grammes. La seconde est une measure de gammadensimétrie, qui permet l'établissement d'un profil de séchage moyen avec une incertitude de 0,4% de masse relative. L'intérêt de cex deux mesures complémentaires est de pouvoir valider pa modélisation du gradient hydrique et de le relier aux déformations que en découlent. Après avoir exposé le principle, la réalisation et la qualification de ces deux méthodes de mesure, l'article présente près d'un an du suivi d'une de ces poutres. Il montre que l'évolution de sa masse respecte une loi en racine carrée du temps et que le front de séchage atteint une profondeur de 80 à 100 mm.

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Editorial Note LCPC is a RILEM Titular Member.     

Measurement of the Sensitivity Function in a Time-Domain Atomic Interferometer

We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave packets. The sensitivity function is calculated in the case of a three-pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at the Laboratoire National de Metrologie et d'Essais-Systeme de References Temps-Espace. We successfully compare this calculation to experimental measurements. The sensitivity of the interferometer is limited by the phase noise of the lasers as well as by residual vibrations. We evaluate the performance that could be obtained with state-of-the-art quartz oscillators, as well as the impact of the residual phase noise of the phase-locked loop. Requirements on the level of vibrations are derived from the same formalism.     

Design and metrological features of microwave synthesizers for atomic fountain frequency standard

In this paper we describe the improved redesign of the microwave frequency synthesizers for Laboratoire National d'Essais-Systèmes de Référence Temps-Espace (LNE-SYRTE) atomic fountains. The synthesizers use a cryogenic oscillator to generate both Cs and Rb hyperfine frequencies based on a new distribution frequency of 1 GHz. The main metrological features (phase noise, long-term phase stability, and spectral purity) of the synthesizers have been measured in situ connected to an atomic fountain and are compatible with an accuracy goal of 10(-16) for the atomic fountains. The simultaneous test of two different synthesizers on the FO2 atomic fountain at the 10(-16) level also is reported.     

Scale effect on concrete in tension

Scale effects in the mechanical behaviour of concrete are important phenomena and are the object of many studies internationally. The Laboratoire Central des Ponts et Chaussées has been working for several years on the scale effect on the distribution function of the tensile strength of concrete. Very many direct tensile tests have been performed on specimens of different volumes, made of concretes having different formulations. From these experimental investigations has been derived a general law that can be used to determine the distribution function (mean and standard deviation) of the tensile strength of the concrete versus the volume of the tensile specimen, for concretes having compressive strengths betwen 30 MPa and 130 MPa, from knowledge of just the compressive strength obtained on a standardized cylinder (in France) and the ratio of the volume of the tensile specimen to the volume of the coarsest aggregate in the concrete. It should be emphasized that this law is valid only if, on the one hand, the mode of preservation of the direct tensile specimens is identical to that of the compressive specimens and, on the other, the aggregates used in the concretes are common aggregates, which eliminates light aggregates and very hard aggregates with a high Young's modulus.

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Resume Les effets d'échelle dans le comportement mécanique du béton sont des phénomènes importants qui font l'object de nombreuses études au niveau international. Le Laboratoire Central des Ponts et Chaussées travaille depuis plusieurs années sur l'effet d'échelle existant sur la fonction de distribution de la résistance à la traction du béton. De très nombreux essais de traction directe ont ainsi été réalisés sur des éprouvettes de volume différent constituées de bétons de formulation également différente. De ces études expérimentales, il a été tiré une loi assez générale qui permet de déterminer, à partir de la seule connaissance de la résistance à la compression obtenue sur cylindre normalisé (en France), et du rapport du volume de l'éprouvette de traction au volume du plus gros grain de béton, la fonction de distribution (moyenne et écart-type) de la résistance à la traction du béton en fonction du volume de l'éprouvette de traction, cela pour des bétons dont la résistance à la compression est comprise entre 30 et 130 MPa. Il faut souligner que cette loi est valable uniquement si, d'une part le mode de conservation des éprouvettes de traction directe est identique à celui des éprouvettes de compression, et d'autre part les granulats utilisés dans les bétons sont des granulats courants, ce qui élimine les granulats légers et les granulats très durs et à fort module de Young.

     

Trilateral Intercomparison of Photometric Units Maintained at NIST (USA), NPL (UK), and PTB (Germany)

A trilateral intercomparison of photometric units between NIST (USA), NPL (UK), and PTB (Germany) has been conducted to update the knowledge of the relationship between the photometric units disseminated in the three countries. The luminous intensity unit (cd), the luminous responsivity scale (A/lx), and the luminous flux unit (lm) maintained at each laboratory were compared by circulating transfer standard lamps and photometers. The results showed that the relative luminous intensity values, with respect to the average, measured by NIST, NPL, and PTB were 1.0014, 1.0021, and 0.9966; the relative inverse values of the luminous responsivity (corresponding to illuminance) were 1.0023, 1.0011, and 0.9965; the relative luminous flux values were 0.9994, 1.0034, and 0.9972, respectively. The results agreed within the stated uncertainties of the units maintained at the three laboratories.     

ACES microwave link requirements

Atomic Clock Ensemble in Space (ACES) is a project of the European Space Agency on-board the future International Space Station (ISS). The payload consists mainly of two atomic frequency standards, one space hydrogen maser (SHM) prepared by the Observatoire de Neuchatel (Switzerland), and one cold atom caesium clock called PHARAO prepared by the CNES (France), with the participation of the BNM-LPTF, the ENS-LKB, and the CNRS-LHA. Because of the anticipated performances of these clocks on-board the ISS, the requirements of the links between the payload and the clocks on the Earth are at the limits of the known potential of the optical or microwave techniques. The microwave link (MWL) requirements are described in this paper. Taking into account the characteristics of the ISS orbit, and fixing an arbitrary limit to the additional noise brought to the clock readings by the MWL, the computation of the required stability leads to two kinds of requirements: the first one at the subpicosecond level over each single continuous pass of the ISS above any Earth station, and the second one at the level of one part in 10(16) and below over a one day or more averaging period. Moreover, the ISS orbit parameters should lead to a knowledge of the ACES clock position at the m level, and of the ACES clock speed at the mm/s level.     

Characterization of Bonner sphere systems at monoenergetic and thermal neutron fields

The Institute for Radiological Protection and Nuclear Safety (IRSN) and the GFR, Universitat Autónoma de Barcelona (UAB) use Bonner spheres (BS) for neutron spectrometry at workplaces. The two systems, equipped with similar cylindrical 3He proportional counters, were simulated with the MCNP Monte-Carlo code to determine the response to neutrons of different energies for each polyethylene sphere. The BS systems were characterized at monoenergetic and thermal neutron fields. Measurements were performed at the Physikalisch-Technische Bundesanstalt (PTB) and at the National Physical Laboratory (NPL) standard laboratories, and with the newly characterized IRSN 'SIGMA' thermal neutron facility. The energy distribution of the reference neutron fluence was folded with the response functions for comparison purposes with the experimental data. In almost all cases related to monoenergetic neutrons, a good agreement between the experimental and the calculated count rates was found, and some discrepancies of a few per cent were observed in the thermal region.     

Recent NPL Work on the AC Josephson Effect as a Voltage Standard

The experimental equipment and procedure used in the latest National Physical Laboratory (NPL) ac Josephson effect determinations of 2e/h are described. The most recent value, obtained in April 1972, is 483 594.00 (±0.10) GHZ/VNPL and this, together with earlier results, provides information concerning the stability of the NPL maintained voltage standard over the past two years. To obtain a further increase in precision, new equipment is being developed for the measurements in which the resistive divider and null detector are maintained at cryogenic temperatures.     

从国际计量机构科研产出看计量领域发展态势——基于文献计量学

采用国际通行的文献计量学的方法,基于2013～2020年Web of Science(WOS)收录的SCI论文数据,研究分析了发达国家计量机构如:美国标准技术研究院 (NIST)、英国国家物理实验室(NPL) 和德国物理技术研究院(PTB)的科研产出,包括论文规模和学科影响力等指标,并进行了对标分析,尝试剖析计量领域科技创新的未来发展态势,同时期望数据背后的趋势和研究结论,能够在我国“十四五”发展中提供参考和支撑。     

Measurement of Infrared Spectral Directional Hemispherical Reflectance and Emissivity at BNM-LNE

An infrared reflectometer has been designed by BNM-LNE (Bureau National de Métrologie–Laboratoire National d’Essais) to measure the spectral directional hemispherical reflectance of solid materials at ambient temperature. For opaque materials, the spectral directional emissivity can be calculated from the measured reflectance. The reflectance can be measured from 0.8 to 14 μm in five directions with an angle of 12°, 24°, 36°, 48°, and 60° with respect to the normal to the surface of the sample. The optical arrangement to collect the reflected flux is based on the Coblentz arrangement (hemispherical mirror). In fact, four mirrors cut in an hemisphere are used to collect the flux reflected by the sample. This optical arrangement was chosen to limit the angle of incidence of rays on the detector (38° instead of 90° for the Coblentz arrangement). The final expanded uncertainty (level of confidence 95%) of the reflectance is estimated to be about ±0.03 for wavelengths between 0.8 and 10 μm and ±0.04 for wavelengths over 10 μm. The values of the spectral reflectance measured on a black paint and on a white ceramic tile are compared to those measured by the two laboratories PTB (Physikalisch Technische Bundesanstalt) and NIST (National Institute of Standards and Technology). The results validate the measurements performed at BNM-LNE. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Comparison of the Josephson voltage standards of VNIIM and PTB

Comparisons of the 1 V Josephson array voltage standard (JAVS) of the “D.I. Mendeleyev Institute for Metrology” (VNIIM), Russia, with that of the Physikalisch-Technische Bundesanstalt (PTB), Germany, were carried out in St. Petersburg in June 1999. The results of the direct comparison agree within an overall standard uncertainty of less than 1 nV. The results also show that direct comparisons are useful for detecting voltage offsets of a few parts in 10¹⁰. The reason for a small voltage offset in an SIS array was investigated at zero voltage level     

A cryogenic open-cavity sapphire reference oscillator with low spurious mode density

In this paper, we describe the implementation of a microwave cryogenic sapphire oscillator (CSO) at the Laboratoire de Physique et Métrologie des Oscillateurs. In our realization we solved the problem of the spurious modes by operating the sapphire resonator in an open cavity. The CSO compared to a hydrogen maser demonstrates a frequency stability better than 3 x 10(-14) at short term. Its long-term frequency instability of the order of 3 x 10(-12)/day is limited by a random walk process. A first attempt to use this reference oscillator to characterize other signal sources is presented.