National Research Laboratory Of Metrology Research Articles

Preflight cross-calibration activities at NRLM

Many satellites have been and will be launched recently for monitoring the Earth-wide circumstances such as the greenhouse effect. The preflight calibration of the satellite radiometers is the key to obtain the high quality data and to analyze the physical quantity precisely. National Research Laboratory of Metrology (NRLM) developed the preflight calibration system for JERS-1 OPS and so on which uses a large integrating sphere as a working standard. The cross-calibration experiment is planned to study the calibration uncertainly and compatibility of integrating spheres for calibrating different radiometers. This paper describes the cross-calibration activities at NRLM among POLDER-OCTS on ADEOS and among ASTER-MODIS-MISR on EOS AM-1.

カルマン渦流量計の渦発生体形状の最適化と不確かさの算出法に関する研究

A vortex shedding flowmeter is widely used for measurements of various fluids in many fields of industry because of its numerous advantages, such as wide rangeability, long term reliability and low maintenance cost. Today, vortex flowmeters of various designs are manufactured by many companies in the world although the flowmeter design is not specified in the present industrial standards. The research project presented in this paper consists of a series of experimental studies and its objective is to develop a new design of a vortex shedding flowmeter, which can be used without any calibration using the actual fluid. This paper describes the first result of the project, i.e. optimization of the flowmeter design and determination of the measurement uncertainty. First, four of the bluff body dimensions were selected and optimized through series of systematic experiments so that the Strouhal number was least dependent on the Reynolds number. Next, the optimized design has been applied to flowmeters with inner diameters from 100mm to 400mm. These flowmeters were calibrated and the Strouhal number was precisely determined. Finally, a new method to calculate the uncertainty of the Strouhal number from the dimensional deviations of the parts of the flowmeter was developed experimentally and analytically. This project has been carried out by National Research Laboratory of Metrology and 10 collaborating companies in Japan. The results shown in this report are obviously very important for future standardization of a vortex flowmeter and for improvement of the accuracy in flow measurement in the world.

The silicon lattice parameter - an invariant quantity of nature?

The lattice parameter of silicon plays an important role in the determination of the Avogadro constant and the fine-structure constant. Today, three values of the d220 silicon lattice spacing are available, measured at the Physikalisch-Technische Bundesanstalt (PTB, Germany), the Istituto di Metrologia "G. Colonnetti" (IMGC, Italy) and the National Research Laboratory of Metrology (NRLM, Japan) and based on the metre scale. Using the PTB lattice spacing comparator, the spacings of the different materials were measured and compared with one another in order to check the possibility of combining the results to form a common "best" value. The characterization of the relevant impurities and crystal defects and their number densities are discussed and corrections applied for their influences on the interatomic distances. The NRLM data are in disagreement with those of the PTB and the IMGC, from which a lattice parameter for a hypothetical, ideal, perfect Si crystal was derived with a relative uncertainty of about .

High-resolution distance meter using optical intensity modulation at 28 GHz

A high-resolution distance meter was fabricated using optical waveguide modulators. An optical intensity modulation frequency of 28 GHz was utilized for the displacement measurement when the driving frequencies to the optical modulators were around 14 GHz. The distance meter was evaluated in the National Research Laboratory of Metrology (NRLM) tunnel, which is a semi-underground tunnel. The measurement resolution is 1 and for a distance of 5 and 100 m, respectively, in one standard deviation after correction of the cyclic error. Furthermore, cyclic errors are examined for 28 GHz optical intensity modulation.

International comparison of a NIST primary standard with an NRLM transfer standard for small mass flow rates of nitrogen gas

International comparisons of small gas flow measurements were carried out between the National Institute of Standards and Technology (NIST) in the United States of America and the National Research Laboratory of Metrology (NRLM) in Japan. An NRLM transfer standard package composed of sonic venturis, two pressure transducers, and two temperature sensors was calibrated using the NRLM primary standard for low gas flows (a gravimetric system) and was brought to the US in April 1996. The NRLM transfer standard was compared with the NIST Fluid Flow Group piston provers (a volumetric system) using mass flow rates of nitrogen between 0.4 g/min and 11.5 g/min. The mean differences between the NRLM transfer standard and the NIST Fluid Flow Group piston provers ranged from -0.09 % to +0.13 %.

High-resolution distance meter using optical modulators at 3.5 GHz

A high-resolution distance meter is fabricated using optical waveguide modulators. The modulation frequencies of the optical modulators are around 3.5 GHz, while the modulation frequencies of the optical intensity are around 7 GHz because the modulation bias voltages are set at the peaks of the electrooptic characteristics. The distance meter was evaluated in the National Research Laboratory of Metrology (NRLM) tunnel, which is a semiunderground tunnel. The measurement resolution has a standard deviation of 12 ?m for a distance range of 0.5 to 5 m after correction of the cyclic error.

Radiometric Measurement Comparison Using the Ocean Color Temperature Scanner (OCTS) Visible and Near Infrared Integrating Sphere.

As a part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan. Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the University of Arizona Optical Sciences Center (UA), and the National Research Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spectral radiance of the OCTS visible and near-infrared integrating sphere at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating sphere when the calibration coefficients for five of the eight spectral channels, or bands, of the OCTS instrument were determined. The measurements of the four radiometers differed by −2.7 % to 3.9 % when compared to the NEC calibration of the sphere and the overall agreement was within the combined measurement uncertainties. A comparison of the measurements from the participating radiometers also resulted in agreement within the combined measurement uncertainties. These results are encouraging and demonstrate the utility of comparisons using laboratory calibration integrating sphere sources. Other comparisons will focus on instruments that are scheduled for spacecraft in the NASA study of climate change, the Earth Observing System (EOS).

Measurements of long gauge blocks using a fringe-counting interferometer and subgauge blocks with lines

A new method for measuring long gauge blocks using a fringe-counting interferometer with a 633 nm wavelength-stabilized He-Ne laser is described. Two subgauge blocks, which have V-type graduation lines covered with glass plates, are optically contacted with both sides of a long gauge block. They are handled with bare hands and the surfaces of the glass plates are wiped with a paper towel after the optical wringing procedure. Using the National Research Laboratory of Metrology 2 m line standard automatic measuring machine, several gauge blocks up to 1 m long are measured with a repeatability less than 0,1 µm in standard deviation. A comparison between the lengths of gauge blocks measured by the new method and by the conventional excess fractions method is made. The results show that the length of gauge blocks up to 1 m can be determined with an expanded uncertainty U = 0,3 µm, corresponding to a level of confidence of about 95 %.

High-speed surface temperature measurements on plasma facing materials for fusion applications

For the lifetime evaluation of plasma facing materials in fusion experimental machines, it is essential to investigate their surface behavior and their temperature responses during an off-normal event such as the plasma disruptions. An infrared thermometer with a sampling speed as fast as 1×10−6 s/data, namely, the high-speed infrared thermometer (HSIR), has been developed by the National Research Laboratory of Metrology in Japan. To evaluate an applicability of the newly developed HSIR on the surface temperature measurement of plasma facing materials, high heat flux beam irradiation experiments have been performed with three different materials under the surface heat fluxes up to 170 MW/m2 for 0.04 s in a hydrogen ion beam test facility at the Japan Atomic Energy Research Institute. As for the results, HSIR can be applicable for measuring the surface temperature responses of the armor tile materials with a little modification. It is also confirmed that surface temperatures measured with the HSIR thermometer show good agreement with the analytical results for stainless steel and carbon based materials at a temperature range of up to 2500 °C. However, for aluminum the HSIR could measure the temperature of the high dense vapor cloud which was produced during the heating due to lower melting temperature. Based on the result, a multichannel arrayed HSIR thermometer has been designed and fabricated.

Direct comparison of copper and gold freezing-point black-body primary standards from the NRLM and the NIST

Freezing-point black bodies used as primary standards of spectral radiance at two national standards laboratories are directly intercompared for the first time. The spectral radiance ratio is directly measured for a copper freezing-point black body from the National Research Laboratory of Metrology (NRLM), Japan, and a gold freezing-point black body from the National Institute of Standards and Technology (NIST), USA. Narrowband spectral radiance measurements at five wavelengths between 546 nm and 878 nm show the NRLM copper to NIST gold freezing-point temperature interval to be 20,39 K ± 0,12 K (2σ), in good agreement with the International Temperature Scale of 1990 (ITS-90) value of 20,44 K, and comfortably within the combined uncertainties assigned to the realization of the ITS-90 from each source.

Absolute Measurement of Lattice Spacing d(220) in Floating Zone Silicon Crystal

The lattice spacing d220 of a silicon crystal of National Research Laboratory of Metrology has been measured with a new combined X-ray and optical interferometer, with relative uncertainty of 0.16 ppm. This value is in good agreement with other reported values, whereas the ratio of molar mass M to density ρ measured for this crystal shows discrepancy of around 3 ppm from previously reported ratios. It seems that the conventional route to determining the Avogadro constant from M, ρ and d220 will require a new characterization technique to estimate the number of silicon atoms in a unit cell volume.

Three-color optical range finding

In the known three-wavelength distance-measuring systems two optical wavelengths are used and a microwave is added for air-humidity influence consideration. In our research, which proceeds from results obtained at the National Research Laboratory of Metrology (Japan), the possibility of constructing a three-optical-wavelength ranging system is discussed. We investigate different versions by using a CO(2) laser as the source of the third wavelength. Analysis shows that the three-wavelength system with two lasers (YAG:Nd(3+) laser, which yields first- and second-harmonic radiation, and a CO(2) laser) seems to be optimum. A possible schematic structure of the three-wavelength YAG-CO(2) laser system is given.

New Mercury Interferometric Baromanometer as the Primary Pressure Standard of Japan

The mercury U-tube manometer is a traditional pressure-measuring instrument and has played an important role as the primary standard in the atmospheric pressure range. It has also been used as the basis of standards for other pressure ranges. About thirty-five years ago, the National Research Laboratory of Metrology developed the precise mercury manometer using a white-light Michelson interferometer to detect the mercury menisci. We now introduce a new mercury U-tube manometer, developed as a national primary standard, to which some improvements and refinements have been added. Though the central principle is the same, the optical path of the reference arm of the interferometer has been redesigned to reduce the index-of-refraction corrections and some improvements have been incorporated to achieve more precise measurements on the U-tube conditions. The pressure range of the new manometer is 116 kPa and the uncertainty at 100 kPa is estimated to be about 0,4 Pa, in both absolute and gauge modes.

Accurate determination of the density of a crystal silicon sphere

For an independent determination of the Avogadro constant, the density of a 1-kg crystal silicon sphere was determined by direct measurements of its mass and volume. A scanning-type interferometer was used to measure the diameters, and the volume was calculated from the mean of uniformly distributed diameters. The sphere was weighted using a balance for the prototype kilogram at the National Research Laboratory of Metrology (NRLM), and the mass was determined accurately by direct measurements of the buoyancy force acting on the sphere. The total uncertainty of the density is estimated to be 0.34 ppm. Effects of a thin oxide layer and impurities on the density of a pure crystal are evaluated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of silicon density standards at NRLM and IMGC

The Istituto di Metrologia 'G Colonnetti' in Torino, Italy, (IMGC) and the National Research Laboratory of Metrology in Japan (NRLM) have developed density standards in the form of single-crystal silicon spheres within their projects for the determination of the Avogadro constant. The results of the first comparison on two such artifacts are presented. The mass and volume of the IMGC sphere were measured at NRLM with an absolute method, whereas , at IMGC, the density of the NRLM sphere was measured by hydrostatic comparison to the IMGC silicon standard. Additional diameter measurements were also made. The overall results show excellent agreement: within 0.16 ppm in density, 0.1 ppm in mass, 0.06 ppm in volume, and 0.04 ppm in diameter measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of the changes in air refractive index and distance by means of a two-color interferometer

<p>We discuss the measurements of the changes in air refractive indices and geometrical distances by means of a two-color phase-modulated fringe-counting interferometer. We analytically classified the optical path lengths for IR and visible light into the changes in the air refractive index and the distance by using a dispersion formula for air. The interferometer was tested over a 235-m path in the testing tunnel of the National Research Laboratory of Metrology, which has a sensor system for measuring air conditions.</p> <p>The refractive-index change by the two-color interferometer agreed with the value calculated by the air conditions within an accuracy of 0.15 ppm.</p>

Intercomparison of Interferometric Dilatometers at NRLM and NPL

Interferometric dilatometers at the National Research Laboratory of Metrology (NRLM) in Japan and the National Physical Laboratory (NPL) in UK been intercompared by measuring the thermal expansion coefficients of pure polycrystalline silicon, a low expansion ceramic (Miraclon) and fused silica (SRM 739). The dilatometers, two from each laboratory, were intercompared over their respective operating temperature ranges of 250 to 375 K and 290 to 800 K. The results presented in this paper show that the agreement for each material is within the combined uncertainties in the measurement of each thermal coefficient of expansion.

流下時間自動計測部を付置した細管式標準粘度計による動粘度測定値の国際的整合性

The viscosity standard in Japan has been established and maintained with capillary master viscometers which are calibrated by the stepping-up method based on the kinematic viscosity of distilled water at 20°C and at atmospheric pressure. In order to improve the accuracy of kinematic viscosity measurements and to extend the temperature ranges of the viscosity standard, new capillary master viscometers with an automatic flow time detection system have been designed and constructed. Then, NRLM (National Research Laboratory of Metrology) has participated in the international comparison of ASTM (American Society for Testing and Materials) standard viscosity liquids organized by ASTM Committee D-02. 07 A since 1984 to confirm the international consistency of the kinematic viscosities determined in the temperature range -40 to 100°C by using new capillary master viscometers.From the results of the comparison, the differences between kinematic viscosities obtained by NRLM and CIC (Cannon Instrument Company, U.S.A.) are -0.28 to 0.20%. The accuracy of kinematic viscosities of the ASTM standard viscosity liquids determined by capillary master viscometers is estimated to be within ±0.05% in two standard deviations.

Precision Physical Measurements and Nanometrology

Precision measurements at the National Research Laboratory of Metrology used to determine fundamental constants and to test physical theory are described: they are related to the determination of silicon lattice spacing; the magnetic flux quantum; and a search for the fifth force. Equipment and techniques for nanometrology are described in terms of the nanoscale, nanoguide and nanodrive, all of which have immediate applications in advanced technology. An example is introduced which demonstrates the power of the scanning tunnelling microscope (STM) in nanometrology.

Characteristics of an optically pumped Cs frequency standard at the NRLM

Characteristics of an optically pumped Cs frequency standard developed at the National Research Laboratory of Metrology (NRLM) are reported. The short-term frequency stability was estimated to be 1.1*10/sup -12// square root pi when the optical feedback technique was used for laser diode stabilization. Frequency shifts due to microwave power and pumping conditions were measured and their characteristics are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>