汞三相点的复现

利用自制的超高纯汞三相点容器,复现了1990年国际温标(ITS-90)中新设定的汞三相点。结果表明其融化范围和凝固范围均在0.1mK以内,复现性优于0.1mK,两者的符合程度也在0.1mK之内,分别用纯度为99.99999％的超高纯商品汞和实验室清洗的汞经高真空蒸馏制备的两个密封容器,测定结果在实验误差内一致,差异不大于0.1mK。文中介绍了三相点容器的制备工艺要点。     

NMIJ Constant-Volume Gas Thermometer for Realization of the ITS-90 and Thermodynamic Temperature Measurement

The constant-volume gas thermometer (CVGT) of the National Metrology Institute of Japan (NMIJ), AIST with ³He as the working gas is used as an interpolating gas thermometer to realize the International Temperature Scale of 1990 (ITS-90) from 3 K to 24.5561 K and as a relative gas thermometer for thermodynamic temperature measurement calibrated at the triple point (TP) of Ne. The standard uncertainties of the realization and measurement are estimated to be 0.58 mK and 0.86 mK at a maximum in the mentioned temperature range, respectively. The maximum difference between both temperatures is about 1 mK. In the calibration of the CVGT, the TP of equilibrium hydrogen (e-H₂) is corrected for isotopic composition as specified in the Technical Annex for the ITS-90. The ambiguity of the TP of Ne due to the variability in isotopic composition is included in the uncertainty. Although the CVGT was also used in 2004 to realize the ITS-90, it was modified for the present experiment to reduce some measurement uncertainty components and the working gas was replaced with a higher-isotopic-purity gas. The results from 2004 were recalculated by correcting for the isotopic composition of e-H₂ and differ insignificantly from the present results, except for a wider scatter.     

Realization of Low-Temperature Fixed Points of the ITS-90 at NMIJ/AIST

A new model of sealed cells with three thermometer wells for calibration of capsule-type thermometers at low-temperature fixed points of the International Temperature Scale of 1990 has been developed at the National Metrology Institute of Japan (NMIJ). The melting curves of Ar and O₂ obtained using the new cells show very flat plateaux and a linear temperature dependence as a function of the inverse liquid fraction (1/F) over the range 1/F = 1 to 1/F = 20 with a narrow melting curve width of 0.1 mK. The melting curves of Ne obtained with the new cell also show very flat plateaux and approximately linear temperature dependence versus 1/F and a narrow melting curve width of 0.1 mK, though with a slight concave structure at high 1/F. The melting temperatures with the new cells agree with previous NMIJ sealed cells within 10 μK, which is similar to the reproducibility of the realization of the triple points at NMIJ. The source dependence of the triple-point temperature of Ne was investigated by filling two of the new cells from different sources of Ne. The difference in the realized triple point temperatures between the two sources is 0.031 mK, consistent with that estimated from isotope analysis. The uncertainties in the calibration of standard platinum resistance thermometers at the low-temperature fixed points are summarized. The uncertainty of the calibration at the triple point of e-H₂ has been reduced to about one-third of its value without the correction by making the isotopic correction on the basis of the technical annex for the ITS-90 in the mise en pratique for the definition of the kelvin.     

Comparison System for the Calibration of Capsule-Type Standard Platinum Resistance Thermometers at NMIJ/AIST

A new comparison system has been constructed using a Gifford- McMahon type cryogenic refrigerator for the calibration of capsule-type standard platinum resistance thermometers (CSPRTs) below 273.16 K at the National Metrology Institute of Japan (NMIJ). The system can compare six CSPRTs at once. A gold-plated comparison block, in which CSPRTs are mounted for calibration, is made from oxygen-free high-conductivity copper. The standard uncertainties related to the temperature control of the system are estimated to be 0.04 mK. The calibrated values for CSPRTs and a rhodium–iron resistance thermometer obtained using the comparison system are in good agreement with those obtained by the direct realization of the low-temperature fixed points of the ITS-90 within the combined standard uncertainty for the calibration using the comparison system.     

镓三相点容器的研制

近年来,镓三相点作为新的温度固定点的研究已经得到了广泛的重视。本介绍了镓三相点容器的制作工艺、冻制过程及复现技术。实验结果表明,镓三相点的温度值为29.7666℃     

Comparison at NMIJ/AIST of the Triple Point of Neon Using Different Sealed Cells

At the National Metrology Institute of Japan (NMIJ), the triple point of neon was measured using an NMIJ sealed cell, NMIJ Ne-5, and a modular sealed-cell model, Ec2Ne, made by the Istituto Nazionale di Ricerca Metrologica (INRiM) in Italy, and the results were compared. The melting curves obtained with the NMIJ Ne-5 cell show narrow widths (0.1 mK) over a wide range of the inverse of the melted fraction (1/F) from 1/F = 1 to 1/F = 10, which is consistent with a previous report. On the other hand, the width of the melting curves obtained with the Ec2Ne cell is 0.15 mK from 1/F = 1 to 1/F = 10. The liquidus point T _tp estimated by the melting curves from F ~ 0.35 to F ~ 0.85 using the NMIJ cell is 0.05 mK higher than that using the Ec2Ne cell. The difference does not agree with the results obtained in an assay of the isotopic concentration from samples of the original Ne sources. The origin of the discrepancy has not been clarified yet.     

镓三相点的复现

本文介绍了镓三相点的复现方法,并对镓三相点值进行测量,其温度值为29．7666℃。     

镓熔点温坪复现研究

镓熔点是ITS-90国际温标中重要的定义固定点,在温度计量研究中起着重要作用。由于高纯镓从液态转化为固态时,体积膨胀约3. 1%,传统玻璃外壳的镓熔点容器在冻制过程中很容易造成损坏。为了解决这一难题,设计了一种具有金属外壳的镓熔点装置,以该装置为对象,开展了2种不同镓熔点复现方法和2种不同复现装置对镓相变温坪影响方面的研究,并与国外同类型装置的性能进行了比较。实验结果表明:不同镓点容器复现的镓熔点温度在0. 02 m K范围内一致,高纯镓中的微量杂质是造成差异的主要原因;外液-固界面复现方法比双液-固界面复现方法得到的温坪值低0. 09 m K;不同复现装置对镓熔点温坪的影响较小。     

Construction of Gallium Point at NMIJ

Two open-type gallium point cells were fabricated using ingots whose nominal purities are 7N. Measurement systems for the realization of the melting point of gallium using these cells were built. The melting point of gallium is repeatedly realized by means of the measurement systems for evaluating the repeatability. Measurements for evaluating the effect of hydrostatic pressure coming from the molten gallium existing during the melting process and the effect of gas pressure that fills the cell were also performed. Direct cell comparisons between those cells were conducted. This comparison was aimed to evaluate the consistency of each cell, especially related to the nominal purity. Direct cell comparison between the open-type and the sealed-type gallium point cell was also conducted. Chemical analysis was conducted using samples extracted from ingots used in both the newly built open-type gallium point cells, from which the effect of impurities in the ingot was evaluated.     

SF6及CO2三相点替代Hg三相点内插方法可行性探究

在不改变90国际温标内插方程形式的基础上,针对83.8058 K到273.16 K温区,分析了六氟化硫(SF6)和二氧化碳(CO2)三相点替代汞(Hg)三相点后,导致的内插方程变化带来的温度偏差以及传播不确定度变化规律.研究结果表明:SF6和CO2三相点替代Hg三相点后,该方程在该温区仍具有适用性;在复现不确定度相同的...     

高准确度水三相点容器

水三相点的高精度复现及准确测量是保证国际温标ITS-90实施的关键。水三相点容器内高纯水的同位素组成会影响复现的水三相点温度值。为了提高水三相点复现水平,减小氢氧同位素的影响,研制了带有氢氧同位素分析的石英及硼硅玻璃高准确度水三相点容器。为了评价容器的性能,开展了硼硅玻璃和石英水三相点容器的比对。实验结果表明:同位素修正前,石英玻璃和硼硅玻璃水三相点容器复现的水三相点在0.058mK范围内一致;同位素修正之后,容器之间的差异在0.017mK范围内一致。采用高准确度水三相点容器复现水三相点的扩展不确定度为0.066mK(k=2)。     

镓三相点的复现

本文介绍了镓三相点的复现方法,并对镓三相点值进行测量,其温度值为29.7666℃.     

Realization of the Triple Point of Water in Metallic Sealed Cells at the LNE-INM/CNAM: A Progress Report

A miniature metallic cell for the water triple point (TPW, temperature 273.16 K) was developed for capsule-type thermometer calibrations for realizations with adiabatic calorimetry techniques. The LNE-INM/Cnam previously developed a copper cell for the water triple point and the techniques for cleaning, filling, and sealing. On the basis of previous work, a new copper cell prototype for the TPW was developed and filled at the LNE-INM/Cnam. Measurements were performed using an appropriate calorimeter and a comparison block containing several thermometers. Preliminary results show a scatter of the temperatures measured at the phase transition of the order of 0.2 mK when measurements are repeated over a short-term period (1 month). A positive drift in the phase transition temperature of about 30μK·month⁻¹ was observed over several months. Studies are in progress to improve the cell, to reduce the reproducibility uncertainty to less than 0.1 mK and to have a phase transition with better temporal stability.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。     

替代汞三相点的研究和新温标展望

从国际温标ITS-90的定义固定点中替代汞三相点,是全球禁止汞的商业交易公约实施的必然结果,也是国际温度计量领域的一个研究热点.要达到替代的目标,候选替代物三相点温坪的计量性能必须达到汞三相点的水平,替代物三相点的复现装置成本可接受、复现技术不复杂;汞三相点被替代后,必然引起温标结构的改变.针对上述问题,对国际温度计量...     

The Realization of Fixed Points of the Temperature Scale in Small-Size Ampoules

Results of an investigation of small-size ampoules of the fixed points of gallium and indium are described. It is concluded that they can be used as an inexpensive standard means of measuring temperature.     

三段控温固定点炉复现铝凝固点研究

固定点炉垂直温场均匀性是影响ITS-90国际温标固定点温坪质量的重要因素.为了提高铝凝固温坪的复现水平,设计了三段控温固定点炉,利用金属外壳铝固定点容器,研究了垂直温场均匀性及其影响因素;在此基础上,采用连续热流密度法高精度复现了铝凝固点.实验结果表明:通过调整上部、中部、下部炉温的设置,可改善固定点炉温场均匀性,铝凝...     

Isotopic Correction of Water-Triple-Point Cells at NMIJ

The twenty-one participating laboratories in the international key comparison of water-triple-point cells (CCT-K7) can be classified into three groups: two laboratories that corrected the effect of the isotopic composition of water, four laboratories that had information on the isotopic composition but did not correct the effect, and the remaining laboratories that had no information. There were significant differences in the realized national standard for the triple point of water (TPW) between those laboratories that applied the isotopic correction and those that did not. The isotopic correction is now considered essential for the triple point of water. Since the National Metrology Institute of Japan (NMIJ) did not apply the isotopic correction and estimated large uncertainties at the time of the CCT-K7 comparison, we subsequently developed new cells for the TPW to improve the reliability and to reduce the uncertainty of the realization as a national reference. The isotopic compositions of seven cells were analyzed, and a chemical impurity analysis of one cell was performed. The good consistency among seven cells was shown in the results obtained when the isotopic correction was applied to the realized temperatures measured experimentally. The expanded uncertainty of the new national reference of NMIJ is estimated to be 49 μK (k = 2), and as a result of this improvement, the expanded uncertainty for calibrating a water-triple-point cell is 80 μK. The previous reference of NMIJ, reported in CCT-K7 to have an expanded uncertainty of 302 μK, is 42 μK lower than the new one. The new reference value is within the uncertainty of the previous national reference, and the new uncertainty is completely covered by the previous uncertainty. Furthermore, the new reference of NMIJ shows good agreement with the national references of the six laboratories able to apply isotopic corrects to their results for CCT-K7. These facts confirm the validity and the linkage to the CCT-K7 of both the previous and the new national references of NMIJ.     

The Influence of Antimony on the Tin Point

In 2005, an agreement was reached on how to estimate uncertainties and how to correct fixed-point temperatures for the influence of chemical impurities. Although the general procedure is now specified, some problems remain. The slope of the liquidus line at very low-impurity concentrations must be extracted either from binary-phase diagrams or from doping experiments. Apart from this, there is little experimental evidence to prove that the models used to characterize the freezing and the melting plateaux are adequate, especially for impurities that increase the fixed-point temperature. Therefore, a series of measurements were carried out using a tin fixed-point cell doped with antimony. By varying the freezing and the melting conditions, some useful experimental data were collected.     

Double Anomalous Peak in the Heat Capacity Just Below the Triple Point of Saturated e-H<Subscript>2</Subscript> with FeO(OH)

The heat capacity of e-H ₂ with powder of FeO(OH) used as a catalyst for ortho-para equilibration has been investigated using sealed cells fabricated at the National Institute of Standards and Technology and at the National Metrology Institute of Japan. An anomalous double peak has been observed in their heat capacities at temperatures just below the triple point independent of sources of H₂ and FeO(OH) and designs of sealed cells. Supercooling behavior has been observed not only at the triple point but also at each anomalous peak resulting from a depression of the melting temperature of a portion of solid H ₂ in close physical proximity to the catalyst. The reduction of the amount of catalyst suppresses the size of the anomalies and allows one to obtain more reliable melting curves for e-H₂ at the triple point.