Estimating the Triple-Point Isotope Effect and the Corresponding Uncertainties for Cryogenic Fixed Points

The sensitivities of melting temperatures to isotopic variations in monatomic and diatomic atmospheric gases using both theoretical and semi-empirical methods are estimated. The current state of knowledge of the vapor-pressure isotope effects (VPIE) and triple-point isotope effects (TPIE) is briefly summarized for the noble gases (except He), and for selected diatomic molecules including oxygen. An approximate expression is derived to estimate the relative shift in the melting temperature with isotopic substitution. In general, the magnitude of the effects diminishes with increasing molecular mass and increasing temperature. Knowledge of the VPIE, molar volumes, and heat of fusion are sufficient to estimate the temperature shift or isotopic sensitivity coefficient via the derived expression. The usefulness of this approach is demonstrated in the estimation of isotopic sensitivities and uncertainties for triple points of xenon and molecular oxygen for which few documented estimates were previously available. The calculated sensitivities from this study are considerably higher than previous estimates for Xe, and lower than other estimates in the case of oxygen. In both these cases, the predicted sensitivities are small and the resulting variations in triple point temperatures due to mass fractionation effects are less than 20 μK.     

An Alternative Method for Manufacturing Water Triple-Point Cells

Water triple-point (WTP) cells are the most important standards in laboratories that calibrate standard platinum resistance thermometers (SPRT). Over the years, different methods for manufacturing WTP cells have been proposed; some quite simple, others more complex. This paper describes a straightforward method for manufacturing WTP cells. The method is based on the fact that the pressure present when water is boiling is its vapor pressure, and because of that the amount of residual dissolved gases, if any, is very small. This makes the use of vacuum pumps unnecessary. The bulb of the WTP cell is filled with pure water produced by multiple distillations or by deionizer systems. The water is then boiled inside the bulb by a furnace built specifically for this purpose. After boiling the water for at least 30 min, the furnace is switched off, and a valve connected to the filling port of the cell is closed, in order to ensure that only water vapor and liquid water are present inside the WTP cell. The cell is then removed from the furnace and sealed when its temperature decreases. The paper also describes the procedure used to evaluate the WTP cells manufactured by this method, through comparisons against other reference standards, manufactured by more traditional approaches. The results show that the temperatures of the WTP cells manufactured by this new method have similar values to the ones obtained in WTP cells manufactured by traditional methods.     

Isotopic Composition of Water Used in Triple-Point Cells

Isotopic analysis of the water used in KRISS triple point of water (TPW) cells was performed by three separate laboratories. The δD and δ ¹⁸O isotopic composition of six ampoules, made from two TPW cells, were analyzed by isotope ratio mass spectrometers. The analysis data showed that δD and δ ¹⁸O were − 62.17‰ and − 9.41‰ for the KRISS-2002-Jan cell, and − 36.42‰ and − 4.08‰ for the KRISS-2005-Jun cell. The temperature deviation of the triple point of water for these cells calculated from Kiyosawa’s data and the definition of the TPW were + 45.07μK for the KRISS-2002-Jan cell, and + 25.49μK for the KRISS-2005-Jun cell. The KRISS TPW temperature was + 92μK higher than the CCT-K7 KCRV after correcting for the deviation of the isotopic composition from Vienna Standard Mean Ocean Water.     

Effect of Impurities on Water Triple-Point Cells

Water triple-point cells are the basis for the definition of the kelvin and for the realization of the International Temperature Scale of 1990. The temperature differences between the cells are mainly caused by impurities arising in the cell water from the dissolution of the cell envelope (borosilicate glass or quartz). In order to investigate the effects of such impurities on the realized triple-point temperature, water triple-point cells doped with known amounts of Si and Na impurities ( \(0.1\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) to \(1\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) of Si and \(0.2\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) to \(2\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) of Na) were manufactured at VSL by adding gravimetric mixtures of a Si standard reference material and ultra high-purity water to the cell high-purity water. Water samples were taken from the manufactured cells, partitioned into three samples, and distributed to different laboratories for isotope and impurity analysis (inductively coupled plasma mass spectrometry, ICPMS). The results of two independent ICPMS analyses were compared with impurity calculations based on the gravimetric data of the prepared mixtures and manufactured cells. One undoped cell manufactured by UME and one undoped cell manufactured by VSL were intercompared at both VSL and SMD to demonstrate the equivalence of the manufacturing processes of UME and VSL. The triple-point temperatures realized by the doped cells and the undoped cell manufactured by VSL were measured at SMD. The results showed that, in doped cells, the equilibration time after the last freezing is directly dependent on the impurity concentration, and the temperature depression of doped triple-point-of-water cells is significantly greater than the values predicted by Raoult’s law for an ideal dilute solution.     

Study on the Difference Between the Triple-Point Temperatures of ^{20}Ne and ^{22}Ne Using Sealed Cells

At the National Metrology Institute of Japan (NMIJ), the triple points of \(^{20}\) Ne and \(^{22}\) Ne were realized using modular sealed cells, manufactured by the Istituto Nazionale di Ricerca Metrologica (INRiM) in Italy to measure the difference of the triple-point temperatures of \(^{20}\) Ne and \(^{22}\) Ne. Standard platinum resistance thermometers (SPRTs) were used that were calibrated by NMIJ on the International Temperature Scale of 1990 (ITS-90). In previous reports, sealed cells of \(^{20}\) Ne and \(^{22}\) Ne were mounted one at a time in a cryostat and their triple points were realized in separate cool-downs (the single-cell measurement). In this study, first, the triple point was realized using the single-cell measurement for \(^{20}\) Ne and \(^{22}\) Ne cells. Second, the \(^{20}\) Ne and \(^{22}\) Ne cells were mounted together on the same copper block and their triple points were realized subsequently one after the other in the same cool-down of the cryostat (the double-cell measurement). The melting curves observed by the single-cell and the double-cell measurements were almost identical for each cell. The difference of the triple-point temperatures between the two cells, \(^{22}T -^{20}\!T\) , was estimated, not only using the subrange of SPRTs defined in the ITS-90 from 13.8033 K to 273.16 K (subrange 1) but also that defined from 24.5561 K to 273.16 K (subrange 2). The difference in \((^{22}T-^{20}\!\!T)\) between the subranges 1 and 2 is within 0.06 mK, which is caused by the subrange inconsistency in the ITS-90. The standard uncertainty in \((^{22}T-^{20}\!T)\) due to the subrange inconsistency is estimated to be 0.017 mK. After correction for the effects of impurities and other isotopes in the \(^{20}\) Ne and \(^{22}\) Ne cells, the difference in the triple-point temperatures between pure \(^{20}\) Ne and pure \(^{22}\) Ne is estimated to be 0.146 64 (5) K on subrange 1, which is consistent within the uncertainty with the former studies. When \(^{22}T-^{20}\!T\) for pure \(^{20}\) Ne and pure \(^{22}\) Ne is estimated on subrange 2, \(^{22}T-^{20}\!\!T\) becomes 0.146 60 (5), which agrees very well with the former reports of INRiM evaluating \(^{22}T-^{20}\!T\) on subrange 2.     

水三相点瓶的国际比对介绍

本文介绍了在1994～2000年间不同国家实验室参加的由国际计量局BIPM组织的水三相点瓶的国际比对.比对结果表明,不同国家实验室所使用的水三相点瓶多数情况下在±0.1mK范围内一致.     

Long Term Performance of Mercury Triple-Point Cells Realized at NIS-Egypt

The triple point of mercury is one of the defining fixed-points of the International Temperature Scale of 1990 (ITS-90). Its value was assigned to be 231.3456 K (?38.8344 °C) by ITS-90 and has a unique importance since it is the only fixed-point suggested by ITS-90 between 0.01 °C and ?190 °C. The thermal metrology laboratory of the National Institute for Standards has chosen, several decades ago, to realize this fixed point through batch of thermometric cells. In the present work, four cells, composing the batch of reference, are inter-compared. The results of these inter-comparisons, over a period of time that may reach a dozen of years, showed the excellent reliability of these cells. One cell of the batch, that is constructed thirty years ago, is still able to materialize a fixed point with an expanded uncertainty of 0.44 mK.     

Comparison of the Argon Triple-Point Temperature in Small Cells of Different Construction

The argon triple point (\(T_{90} = 83.8058\,\hbox {K}\)) is a fixed point of the International Temperature Scale of Preston-Thomas (Metrologia 27:3, 1990). Cells for realization of the fixed point have been manufactured by several European metrology institutes (Pavese in Metrologia 14:93, 1978; Pavese et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Hermier et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The Institute of Low Temperature and Structure Research has in its disposal a few argon cells of various constructions used for calibration of capsule-type standard platinum resistance thermometers (CSPRT) that were produced within 40 years. These cells differ in terms of mechanical design and thermal properties, as well as source of gas filling the cell. This paper presents data on differences between temperature values obtained during the realization of the triple point of argon in these cells. For determination of the temperature, a heat-pulse method was applied (Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The comparisons were performed using three CSPRTs. The temperatures difference was determined in relation to a reference function \(W(T)=R(T_{90})/R(271.16\hbox {K})\) in order to avoid an impact of CSPRT resistance drift between measurements in the argon cells. Melting curves and uncertainty budgets of the measurements are given in the paper. A construction of measuring apparatus is also presented in this paper.     

EURAMET.T-K7 Key Comparison of Water Triple-Point Cells

The results of a EURAMET key comparison of water triple-point cells (EURAMET.T-K7) are reported. The equipment used, the measuring conditions applied, and the procedures adopted for the water triple-point measurement at the participating laboratories are synthetically presented. The definitions of the national reference for the water triple-point temperature adopted by each laboratory are disclosed. The multiplicity of degrees of equivalence arising for the linking laboratories with respect to the ??mother?? comparison CCT-K7 is discussed in detail.     

密封连接结构的高压低温漏率测试

研制了一套密封连接结构的检漏装置，它可以检测密封连接结构在液氢温度与高压下的漏率。另外还报道了漏率测试方法与试验结果。     

低温离心机温度参数校准

低温离心机是核酸检测实验室基本的仪器,主要用于血液离心和DNA、RNA样品核酸提取.低温离心机的温度控制性能,是离心萃取和样本裂解的关键参数,其温度参数直接影响实验室检测结果的可靠性.在使用低温离心机之前,对低温离心机的进行温度校准,是保证实验室试验结果准确的重要环节.采用有线温度巡检仪校准方法是在离心机腔底部离转子较近处设温度传感器,通过测量离心腔底部空气温度间接测量转子内试样所处腔内温度,这种方法无法准确地测量离心过程中的试样所处腔内温度变化,测试结果误差大、准确度低.通过无线温度验证系统,配以精准的布点方式,可以准确测量离心机运转时的温度参数.     

Improved Thermal Model for the Realization of the Triple Points of Cryogenic Gases as Temperature Fixed Points

The realization of the triple points of the cryogenic gases hydrogen, neon, oxygen, and argon as temperature fixed points at the highest level of accuracy requires consideration of the special properties of these fixed-point substances, as done in a general measurement protocol published elsewhere. The protocol is applied to the apparatus and methodology used for an international star intercomparison of sealed fixed-point cells. A generalized thermal model is developed to include the coexistence of different solid?Cliquid interfaces and various thermal resistances. This results in further components in the detailed uncertainty budget for the correction of the measuring power of the thermometer and for the extrapolation to the liquidus point. As a basis for an optimum fixed-point realization, especially an explanation is given why extremely long time periods may be necessary for the thermal recovery after pulses of the intermittent heating used for the calorimetric method.     

用密封式三相点容器复现氖三相点

介绍了用密封式三相点容器在低温恒温器中复现氖三相点的方法和结果.在研究中采用了多容器结构,它包含有平衡氢、氖、氧和氩密封三相点容器各一个,可在同一个恒温器中依次进行复现.对应这种多容器结构,中国计量科学研究院设计和建立了新的高精度的低温恒温器.对氖三相点测量结果的复现性为0.1 mK,扩展不确定度为0.14 mK.     

Investigation of Doped Inert Gas Solids for Cryogenic Lasers

Inert gas polycrystalline samples containing about 0.05–0.5% of dopants such as neutral excimers XeF, KrF, NeF, and ionic excimers Rb²⁺F^–, Cs²⁺F^–, Cs²⁺Cl^–, and also molecules CO-Hg, NO, N₂O and ¹³CO₂ are considered as active media for cryogenic lasers emitting in a broad wavelength range from VUV through VIS into far IR. A correlation between the values of the oscillator strength f in the range of 0.4–10^–6, the cross section for stimulated emission between 10^–15–10^–17 cm² and the pump energy density at laser threshold (10^–3–10^–2 J/cm³) confirms the lasing potential of the systems XeF/Ar (B-X, 411 nm) and of those emitting in IR in agreement with experiment. For the deep UV and VUV transitions B-X of alkalihalides in solid Ne (196.5 nm, 220.1 nm, 136 nm) high pumping thresholds are derived despite of high f values because of large line width.     

Ultra-High-Speed Methods of Measurement for the Investigation of Breakdown Development in Gases

Several electrical and optical methods of measurement for the investigation of breakdown development in gases are described. Thereby not the sensitivity but the temporal resolution is emphasized. For this reason especially the fast voltage collapse at the gap and the corresponding current rise can be investigated. This is even true in highly compressed gases. Furthermore, the exact synchronization of electrical and optical test methods is described. By this way both the temporal and the spatial discharge development can be investigated simultaneously.     

Experimental Investigations of the Critical Parameters of the Initiated Ignition of Gases

The theory and a calorimetric method of measuring the minimum ignition energy of gases are described.     

The Effect of the Cryosurface Materials on the Cryoemission Parameters of Some Gases

The results obtained are an experimental confirmation of the effect of the cryosurface material on the process of the onset of cryocondensation radiation during the condensation of gases such as nitrous oxide, ethanol, and methanol. It is shown that regardless of the material of the optical system of the surface, whether it is a metal mirror or a mirror covered with a film of the cryocondensates of a dielectric having an intrinsic dipole moment or with a zero-dipole moment while maintaining the thermodynamic parameters and formation conditions, the cryoradiation process will exist in the visible spectral range. This fact is a constructive proof of selection and calculation of low-temperature surfaces in specific conditions of their functioning.