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In this work, the consistency of the heat pulse-based melting technique, which was used to determine the liquidus temperature of tin, was examined by comparing the liquidus temperatures of tin at 101 325 Pa and at the vapor pressure of tin (i.e. the triple-point temperature), both of which were realized by the heat pulse-based melting. Periodic square wave-type temperature steps with an amplitude of 0.7 °C were generated in the isothermal region of the pressure-controlled loop heat pipe, and the tin sample, having a segregated impurity distribution established by the prior outward slow freezing, was melted by application of the temperature step-based heat pulses. The triple point temperature was found to be lower than the liquidus temperature of tin at 101 325 Pa by 3.23 mK with an expanded measurement uncertainty of 0.24 mK (i.e. a coverage factor of k = 2), while the ideal temperature difference calculated from the ITS-90 given pressure coefficient (i.e. 3.3 × 10-8 K/Pa) is about 3.34 mK. The difference between the measured temperature difference and the ideal temperature difference was attributed to the incomplete removal of the gases in the tin triple-point cell. Overall, the heat pulse-based melting technique was shown to yield results consistent with the prescription of the ITS-90, and to be a reliable method in terms of the realization of the fixed-point temperatures.

Recent experiments [J. Guo et al., Phys. Rev. Lett.124,206602 (2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu$_2$(BO$_3$)$_2$ -- the Shastry-Sutherland material -- have provided strong evidence for a low-temperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model [B. Zhao et al., Nat. Phys. 15, 678 (2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu$_2$(BO$_3$)$_2$. Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two order phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple points. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu$_2$(BO$_3$)$_2$ exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes., Comment: 14 pages, 8 figures

In this study, we realized the triple point (TP) temperature of sulfur hexafluoride (SF6) at the National Institute of Metrology (NIM), China. To this end, we designed an iso-thermal and immersion type apparatus with an open cell with a height of 18 cm, diameter of 5 cm, and a capacity of approximately 275 ml. The cell was designed with four thermometer wells for the simultaneous temperature measurements with four standard platinum resistance thermometers (SPRTs). The cell is connected with two buffer tanks that allow a sufficient amount of SF6 to surround the thermometer wells during the solidification and melting processes to ensure stable temperature plateaus with long durations. An SF6 sample with a purity of 99.9997%, which is the highest purity currently available, was supplied and analyzed from the Korea Research Institute of Standards and Science. The SF6 TP temperature was determined using four long-stem SPRTs. The melting plateaus obtained had a duration longer than 15 h, and the TP temperature of SF6 was determined to be 223.556 03(54) K (k = 1). These results are consistent with those of previous studies and further indicate that the SF6 TP is a good candidate to replace mercury TP, which is one of the fixed points defined in the International Temperature Scale of 1990, for the calibration of SPRTs.

Producción Científica, A new determination of the molar gas constant was performed from measurements of the speed of sound in argon at the triple point of water and extrapolation to zero pressure. A new resonant cavity was used. This is a triaxial ellipsoid whose walls are gold-coated steel and which is divided into two identical halves that are bolted and sealed with an O-ring. Microwave and electroacoustic traducers are located in the northern and southern parts of the cavity, respectively, so that measurements of microwave and acoustic frequencies are carried out in the same experiment. Measurements were taken at pressures from 600 kPa to 60 kPa and at 273.16 K. The internal equivalent radius of the cavity was accurately determined by microwave measurements and the first four radial symmetric acoustic modes were simultaneously measured and used to calculate the speed of sound. The improvements made using the new cavity have reduced by half the main contributions to the uncertainty due to the radius determination using microwave measurements which amounts to 4.7 parts in 106 and the acoustic measurements, 4.4 parts in 106, where the main contribution (3.7 parts in 106) is the relative excess half-widths associated with the limit of our acoustic model, compared with our previous measurements. As a result of all the improvements with the new cavity and the measurements performed, we determined the molar gas constant R = (8.314449  0.000056) J·K-1·mol-1 which corresponds to a relative standard uncertainty of 6.7 parts in 106. The value reported in this paper lies -1.3 parts in 106 below the recommended value of CODATA 2014, although still within the range consistent with it., 2018-08-10, MEC ENE2013-47812-R, Junta de Castilla y León VA035U16

Three mixtures of argon in oxygen with (1000, 350, 120) μmol mol−1 amount fractions of argon were prepared by the gravimetric method for application to thermometry. The mixtures are to be used to study the effects of argon impurity in oxygen on the temperature of the triple point of oxygen. From an uncertainty assessment compliant with the international standards, the relative uncertainty of the amount fraction of argon in the two-step dilution method used in this work ranged from 0.040% to 0.072%. The uncertainty was dominated by the uncertainties in weighing the mass of argon in the pre-mixture and weighing the mass of the pre-mixture in the final mixture. The internal consistency of the amount fraction of argon given by the gravimetric method was verified to be within 0.025% by measurements via gas chromatography with a thermal conductivity detector. The resultant uncertainty in the amount fraction of argon corresponds to less than 5 μK in the effect of argon impurity on the triple point of oxygen. Therefore, the mixtures have sufficient precision for the thermal study of the argon-in-oxygen mixtures.

We describe measurements of thermodynamic temperature in the range 5 K to 24.5561 K (the triple point of neon) using single-pressure refractive-index gas thermometry (SPRIGT) with 4He. In the wake of the May 2019 re-definition of the kelvin and its associated mise en pratique, the main purpose of the work is to provide values of T–T 90, the discrepancy between thermodynamic temperature and that of the International Temperature Scale of 1990 (ITS-90). The link to ITS-90 is made via calibrated rhodium-iron resistance thermometers. Innovations required to reach the level of accuracy required for meaningful measurements (uncertainty in T–T 90 less than the expected deviation) include the suppression of temperature oscillations in a cryogen-free cryostat, a pressure stabilization scheme based on a non-rotating piston balance, modelling of the hydrostatic head correction and refinements of the measurement of microwave resonances in a quasi-spherical copper resonator. The accuracy of measurements varies from 0.05 mK to 0.17 mK and is competitive with that of all previous ones in this temperature range using other techniques. The improvement stems partly from the new techniques used for the new definition of the kelvin as well as ab initio calculations of the thermophysical properties ofgaseous 4He. In addition to confirming the validity of SPRIGT as an accurate, easier-to-implement alternative to other low-temperature primary thermometry techniques (e.g. acoustic gas thermometry) yet with scope for improvement, the results should provide important input data for any future revision of ITS-90.

A cryogenic fixed point cell has been filled with high purity (99.999%) sulfur hexafluoride (SF6) and measured in an adiabatic closed-cycle cryostat system. Temperature measurements of the SF6 melting curve were performed using a capsule-type standard platinum resistance thermometer (CSPRT) calibrated over the International Temperature Scale of 1990 (ITS-90) subrange from the triple point of equilibrium hydrogen to the triple point of water. The measured temperatures were corrected by 0.37 mK for the effects of thermometer self-heating, and the liquidus-point temperature estimated by extrapolation to melted fraction F = 1 of a simple linear regression versus melted fraction F in the range F = 0.53 to 0.84. Based on this measurement, the temperature of the triple point of sulfur hexafluoride is shown to be 223.555 23(49) K (k = 1) on the ITS-90. This value is in excellent agreement with the best prior measurements reported in the literature, but with considerably smaller uncertainty. An analysis of the detailed uncertainty budget of this measurement suggests that if the triple point of sulfur hexafluoride were to be included as a defining fixed point of the next revision of the International Temperature Scale, it could do so with a total realization uncertainty of approximately 0.43 mK, slightly larger than the realization uncertainties of the defining fixed points of the ITS-90. Since the combined standard uncertainty of this SF6 triple point temperature determination is dominated by chemical impurity effects, further research exploring gas purification techniques and the influence of specific impurity species on the SF6 triple point temperature may bring the realization uncertainty of SF6 as a fixed point material into the range of the defining fixed points of the ITS-90.

This paper is the second of two articles on the quantification of isotope effects on the triple point temperature of water. In this second article, we address the combined effects of 18O and 17O isotopes. We manufactured five triple point cells with waters with 18O and 17O abundances exceeding widely the natural abundance range while maintaining their natural 18O/17O relationship. The 2H isotopic abundance was kept close to that of VSMOW (Vienna Standard Mean Ocean Water). These cells realized triple point temperatures ranging between −220 μK to 1420 μK with respect to the temperature realized by a triple point cell filled with VSMOW. Our experiment allowed us to determine an accurate and reliable value for the newly defined combined 18, 17O correction parameter of AO = 630 μK with a combined uncertainty of 10 μK. To apply this correction, only the 18O abundance of the TPW needs to be known (and the water needs to be of natural origin). Using the results of our two articles, we recommend a correction equation along with the coefficient values for isotopic compositions differing from that of VSMOW and compare the effect of this new equation on a number of triple point cells from the literature and from our own institute. Using our correction equation, the uncertainty in the isotope correction for triple point cell waters used around the world will be

For use in a low-temperature region below the triple point of water (TPW), the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) developed a precise comparison system of capsule type standard platinum resistance thermometers (CSPRTs) for dissemination of the International Temperature Scale of 1990 (ITS-90). This study compared eight CSPRTs with a reference CSPRT using the comparison system to study non-uniqueness at the low temperature. We also evaluated characteristics of new type of low-temperature platinum resistance thermometers with about 1000 Ω of resistance at TPW (PT-1000), which was recently developed by Netsushin Co. Ltd. to obtain better temperature sensitivity of resistance at a low temperature. The PT-1000 sensor is made from a high-grade platinum wire, similarly to standard platinum resistance thermometers of the ITS-90. We calibrated four PT-1000s based on the ITS-90 and evaluated their characteristics by comparison with a reference CSPRT. Results indicate that the character of the temperature scale of PT-1000s is very close to that of CSPRTs down to 14 K.

We present an experimental study of the high-pressure, high-temperature behaviour of cerium up to ∼22 GPa and 820 K using angle-dispersive x-ray diffraction and external resistive heating. Studies above 820 K were prevented by chemical reactions between the samples and the diamond anvils of the pressure cells. We unambiguously measure the stability region of the orthorhombic oC4 phase and find it reaches its apex at 7.1 GPa and 650 K. We locate the α-cF4–oC4–tI2 triple point at 6.1 GPa and 640 K, 1 GPa below the location of the apex of the oC4 phase, and 1–2 GPa lower than previously reported. We find the α-cF4 → tI2 phase boundary to have a positive gradient of 280 K (GPa)−1, less steep than the 670 K (GPa)−1 reported previously, and find the oC4 → tI2 phase boundary to lie at higher temperatures than previously found. We also find variations as large as 2–3 GPa in the transition pressures at which the oC4 → tI2 transition takes place at a given temperature, the reasons for which remain unclear. Finally, we find no evidence that the α-cF4 → tI2 is not second order at all temperatures up to 820 K.

We performed a precise temperature measurement of the triple point of carbon dioxide (CO2), which is one of the secondary reference points of the International Temperature Scale of 1990 (ITS–90), using an adiabatic calorimeter with five capsule-type standard platinum resistance thermometers (SPRTs). Impurity analyses showed that the purity of the CO2 sample was 99.999 37%. A thermal treatment process before the realization of the triple point reduced the width of the melting curve of the triple point of CO2 and increased the linearity of the melting curves with respect to the inverse of the melting fraction F. We determined the triple-point temperature of CO2 at the liquidus point by extrapolating the six melting curves obtained after the thermal treatment process. The triple-point temperature of CO2 measured in this work is 216.590 90 K 0.36 mK (k = 1). This result indicates that the triple point of CO2 can potentially be used as a fixed point based on the ITS–90 to replace the triple point of mercury.

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.

The principles, techniques and results from dielectric-constant gas thermometry (DCGT) are reviewed. Primary DCGT with helium has been used for measuring T–T90 below the triple point of water (TPW), where T is the thermodynamic temperature and T90 is the temperature on the international temperature scale of 1990 (ITS-90), and, in an inverse regime with T as input quantity, for determining the Boltzmann constant at the TPW. Furthermore, DCGT allows the determination of several important material properties including the polarizability of neon and argon as well as the virial coefficients of helium, neon, and argon. With interpolating DCGT (IDCGT), the ITS-90 has been approximated in the temperature range from 4 K to 25 K. An overview and uncertainty budget for each of these applications of DCGT is provided, accompanied by corroborating evidence from the literature or, for IDCGT, a CIPM key comparison.

We have determined the acoustic and microwave frequencies of a misaligned spherical resonator maintained near the temperature of the triple point of water and filled with helium with carefully characterized molar mass g mol−1, with a relative standard uncertainty . From these data and traceable thermometry we estimate the speed of sound in our sample of helium at K and zero pressure to be m2 s−2 and correspondingly deduce the value J mol−1 K−1 for the molar gas constant. We estimate the value J K−1 for the Boltzmann constant using the currently accepted value of the Avogadro constant NA. These estimates of R and k, with a relative standard uncertainty of 1.06 × 10−6, are 1.47 parts in 106 above the values recommended by CODATA in 2010.

An acoustic gas thermometer was used to achieve a determination of the Boltzmann constant, kB, using a misaligned stainless steel (316L) spherical cavity with an internal volume of approximately 268 cm3. Measurements of the speed of sound while the cavity is filled with argon at the temperature of the triple point of water, 273.16 K, and at different pressures between 78.2 kPa and 0.9 MPa, were used to extrapolate the value of the speed of sound in argon at zero pressure. The internal volume of the resonator was accurately determined by measuring microwave resonance frequencies at the same temperature and pressure conditions as for the acoustic measurements. The measurements were taken at pressures from 78.2 kPa up to 901.3 kPa, and at 273.16 K. As the results of the measurements, we determined kB = (1.380 644 1 ± 0.000 022 1) × 10−23 J K−1 which means a relative standard uncertainty of 16 parts in 106.

In an effort to further reduce the uncertainties in the triple point temperatures of 20Ne and 22Ne, already established in previous publications, at INRIM a cell for each of the two high-purity isotopes was mounted on the same copper block and their triple points were realized subsequently one after the other, allowing a reduction of the total experimental uncertainty on their temperature difference due to a full correlation of some of the uncertainty components arising from this type of realization. The two meltings remain perfectly distinct and do not interfere with each other, being the temperature difference of 0.147 K while the melting ranges are below 0.2 mK. The main difference with respect to single measurements (mounting a single cell at a time), lies in the adiabatic conditions during measurement, which are hardly reproducible when mounting a single cell at a time, leading to one of the dominant uncertainty contributions, 15 μK (single). In the present work, the uncertainty component due to the adiabatic conditions is reduced by using a measurement in sequence (mounting the two cells at a time), 1 μK. Thus, an improved reliability in the experimental realization is obtained as reflected in the experimental contributions to the uncertainty budget.

The neon triple point is one of the defining fixed points of the International Temperature Scale of 1990 (ITS-90). Although recognizing that natural neon is a mixture of isotopes, the ITS-90 definition only states that the neon should be of ?natural isotopic composition?, without any further requirements. A preliminary study in 2005 indicated that most of the observed variability in the realized neon triple point temperatures within a range of about 0.5?mK can be attributed to the variability in isotopic composition among different samples of ?natural? neon. Based on the results of an International Project (EUROMET Project No. 770), the Consultative Committee for Thermometry decided to improve the realization of the neon fixed point by assigning the ITS-90 temperature value 24.5561?K to neon with the isotopic composition recommended by IUPAC, accompanied by a quadratic equation?to take the deviations from the reference composition into account. In this paper, the uncertainties of the equation?are discussed and an uncertainty budget is presented. The resulting standard uncertainty due to the isotopic effect (k = 1) after correction of the calibration data is reduced to (4 to 40)??K when using neon of ?natural? isotopic composition or to 30??K when using 20Ne. For comparison, an uncertainty component of 0.15?mK should be included in the uncertainty budget for the neon triple point if the isotopic composition is unknown, i.e. whenever the correction cannot be applied.

It is widely recognized that the Mercury triple point (MTP) being situated very close to the Water triple point (WTP) constitutes a weakness in the International Temperature Scale of 1990 (ITS-90), in addition to safety concerns related to the use and transportation of Mercury. As such, a substitution for a safer, high-quality fixed point about half way between the Argon and Water triple points would be highly desirable. Now, a direct comparison is described of a Xenon cell filled in 2005 by the National Research Council Canada (NRC) and a more recently produced cell of the Istituto Nazionale di Ricerca Metrologica (INRIM). The present paper discusses the INRiM 2017 measurements on both the INRiM and NRC cells, with a follow-up measurement at NRC, and presents the difference between the two cells, (0.17 ± 0.08) mK with the uncertainties of each cell's realization of the Xenon triple point (XeTP), 0.11 mK for the INRiM cell and 0.07 mK for the NRC cell (k = 1). In addition, the effect of substituting Mercury with Xenon on Type 1 non-uniqueness ('SRI', subrange inconsistency), Type 3 non-uniqueness ('NU3', cSPRT variability) and propagation of fixed point realization uncertainty is shown and discussed.

Similar to Weyl fermions, a recently discovered topological fermion "triple point" can be generated from the splitting of Dirac fermion while the system has inversion symmetry (IS) breaking or time reversal symmetry (TRS) breaking. Inducing triple points in IS breaking symmorphic systems have been well studied, whereas in TRS breaking symmorphic systems have not yet. In this work, we extend the theory of searching triple points to all symmorphic magnetic systems. We list all $k$ paths of all symmorphic systems which allow the existence of triple points. With this systematic study, we also find out that the coexistence of Dirac points and triple points is symmetrically allowed in some particular symmetric systems. Our works will not only be helpful for searching triple points but also extend the knowledge of such a new topological fermion.

The long-term stability of standard platinum resistance thermometers (SPRTs) in a temperature range between 0.01 ◦ C and 419.527 ◦ C was investigated from 352 samples of data accumulated from fixed-point calibration conducted during a period of eleven years. The rates of change of resistance RTPW at the triple point of water and the resistance ratio at the freezing point of Sn (WSn) and Zn (WZn) were analysed. For 75% of the samples investigated, the rate of change of RTPW was within 5.17 mK/year in magnitude. For the same portion of SPRTs, the rates of change in WSn and WZn were within 0.82 mK/year and 1.69 mK/year, respectively. Further statistical investigation showed that measurement at the triple point of water only was not a sufficient test to identify the change in WSn or WZn. However, due to the strong correlation between the changes in WSn and WZn, measurement of the resistance ratio at one of the fixed points in the range of usage is adequate to identify possible change in the entire range of usage.

The Boltzmann constant has been determined by performing isotherm measurements around the triple point of neon with dielectric-constant gas thermometry (DCGT). The necessary thermodynamic reference has been established with an uncertainty of about two tenths of a millikelvin, via realizing the International Temperature Scale of 1990, ITS-90, and exploiting the recently published results for the deviation between thermodynamic temperature and the ITS-90. In combination with a detailed treatment of uncertainty estimates and correlations, a value for the Boltzmann constant of kLT = 1.380 657 × 10−23 J K−1 with a standard uncertainty of 15.9 parts per million (ppm) has been determined. This value deviates from the CODATA value, published in 2008, by only 4.7 ppm and is in very good agreement with the value obtained by DCGT at the triple point of water kTPW = 1.380 654 × 10−23 J K−1 with an uncertainty of 9.2 ppm. The weighted mean of kLT and kTPW leads to the DCGT estimate for the Boltzmann constant of k = 1.380 655 × 10−23 J K−1 with an uncertainty of 7.9 ppm.

Within an international project directed to the new definition of the base unit kelvin, the Boltzmann constant k has been determined by dielectric-constant gas thermometry at PTB. In the pressure range from about 1 MPa to 7 MPa, 11 helium isotherms have been measured at the triple point of water (TPW) by applying a new special experimental setup consisting of a large-volume thermostat, a vacuum-isolated measuring system, stainless-steel 10 pF cylindrical capacitors, an autotransformer ratio capacitance bridge, a high-purity gas-handling system including a mass spectrometer, and traceably calibrated special pressure balances with piston–cylinder assemblies having effective areas of 2 cm2. The value of k has been deduced from the linear, ideal-gas term of an appropriate virial expansion fitted to the combined isotherms. A detailed uncertainty budget has been established by performing Monte Carlo simulations. The main uncertainty components result from the measurement of pressure and capacitance as well as the influence of the effective compressibility of the measuring capacitor and impurities contained in the helium gas. The combination of the results obtained at the TPW (kTPW = 1.380 654 × 10−23 J K−1, relative standard uncertainty 9.2 parts per million) with data measured earlier at low temperatures (21 K to 27 K, kLT = 1.380 657 × 10−23 J K−1, 15.9 parts per million) has yielded a value of k = 1.380 655 × 10−23 J K−1 with uncertainty of 7.9 parts per million.

APMP.T-K7.1, was held from July 2014 to May 2015 to compare the national realizations of the water triple point between NMIJ (Japan) and VMI (Vietnam). To reach the objective, VMI sent a transfer cell to NMIJ and stated a value for the temperature difference of the transfer cell, relative to the corresponding national standard, representing 273.16 K. This report presents the results of the TPW comparison, gives detailed information about the measurements made at the NMIJ and at the VMI, and aims to link the results of APMP.T-K7.1 to APMP.T-K7 and CCT-K7. The results of this key comparison are also represented in the form of degrees of equivalence for the purposes of the MRA. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The basic possibility of creation of high speed cryogenic monodisperse targets is shown. According to calculations at input of thin liquid cryogenic jets with a velocity of bigger 100 m/s in vacuum the jets don't manage to freeze at distance to 1 mm and can be broken into monodisperse drops. Drops due to evaporation are cooled and become granules. High speed cryogenic monodisperse targets have the following advantages: direct input in vacuum (there is no need for a chamber of a triple point chamber and sluices), it is possible to use the equipment of a cluster target, it is possible to receive targets with a diameter of D 100m/s), exact synchronization of the target hitting moment in a beam with the moment of sensors turning on.

The oxidization characteristics of some standard platinum resistance thermometers are discussed on the basis of the Gibbs free energy diagram of the platinum-oxygen ensemble. The oxidization characteristics are estimated from the measurement of the resistance changes at the triple point of water. The resistance changes of thermometers are caused by pure chemical reactions of Pt to PtO2, PtO2 to PtO, and the deoxidization. The oxidized platinum of PtO on the platinum sensing wire does not grow directly from Pt but through PtO2. This hysteresis in the formation of PtO makes the resistance characteristics of the thermometers complicated, particularly in the range above 300 °C.

Instabilities of the order of 50 µK or higher have been observed in water triple point cells with a thermometer well of 12 mm to 13.6 mm diameter during measurements at the INRiM in the framework of the Euromet.T-K7 comparison. In the course of many follow-up measurements, extending over more than one year, these anomalies have been investigated and a solution has been tried and verified. The use of quartz bushings has been tried, leading to a much closer agreement between water triple point cells of different dimensions than was hitherto achieved. Furthermore, the effect on the realized triple point temperature is shown, when no bushing is used.

The adoption of a non-uniform dopant profile has substantially increased the tolerance to high mode deformations of our baseline indirect-drive design. In addition, a low deuterium–tritium (DT) gas density, obtained by 'dynamic quenching' at 2.3 K below triple point, could partly compensate for the decrease in robustness due to DT ageing. Finally, the net margin regarding all laser and target technological defects is about 2. As soon as a sufficient amount of laser beams and diagnostics is available, we will shoot pre-ignition experiments to tune the point design. We are studying new targets which need less energy for these campaigns.We have estimated different direct-drive schemes using indirect-drive beams. The optimal LMJ polar direct-drive configuration is a 2-cone one and leads to marginally igniting targets. A new 2-cone direct-drive scheme, associated with focal spot zooming, allows us to reach ignition with enough margin.

We present accurate measurements of the triple point of nitrogen. The quality of this triple point is once more confirmed, and its temperature value is found to be T90 = 63.152 6 K (expanded uncertainty U = 0.30 mK, reproducibility better than 0.1 mK). This is the first direct determination of this point on ITS-90 since the introduction of the scale. This point is useful as a non-uniqueness checkpoint.

Calibrated standard platinum resistance thermometers (SPRTs) are used to realize the International Temperature Scale of 1990 (ITS-90) from 13.8033 K to 1234.93 K. The SPRTs are calibrated at a series of fixed points, each assigned a temperature on the ITS90, by measuring the ratios of the SPRT resistances at those temperatures to that at the triple point of water (TPW). For realizing the scale with a calibrated SPRT, a user measures the resistance ratio at the unknown temperature and uses ITS-90-defined equations to interpolate between fixed points. The uncertainty of the SPRT temperature is therefore largely influenced by the propagation of fixed-point resistance-ratio uncertainties. In this paper, we rigorously derive the equations for calculating these uncertainties for a variety of circumstances and we use software tools written by us to perform these calculations using realistic uncertainties for fixed points and other input parameters. For properly calculating the standard uncertainty for SPRT realization of the ITS-90, correlations between the input quantities must be considered, in particular those involving measurement of the TPW resistance. The proper calculation depends on three factors involving SPRT use and calibration. The different combinations of these factors result in six different equations for calculating the realization uncertainty. We derive these six equations, specify the conditions of their use and discuss the relevant uncertainty components for each of them. We also compare the results of these equations with those of two approximations that may be used for calculating the standard uncertainty and explain the conditions under which the simpler approximations agree with the more detailed calculations. Because these calculations are complicated, we are making our software tools available upon request to the user community.

The present definition of the kelvin links the unit of temperature with a material property, namely the triple point temperature of water. It would be more consistent with the current approaches to other base units of the International System of Units to fix the value of the Boltzmann constant k, instead. This would rationalize the definition and make it separate from any technique of realization. Furthermore, it is needed to improve temperature measurement, particularly at temperatures far away from the triple point of water. For this purpose, k must first be determined with appropriately small uncertainty applying different measurement methods. In this paper, the primary-thermometry methods for determining the Boltzmann constant (acoustic gas thermometry, thermal-equation-of-state methods, radiation thermometry and methods based directly on statistics and quantization) and their state-of-the-art level of uncertainty are discussed. Special emphasis is given to the basic physics underlying these methods, the fundamental error sources and the uncertainty, which seems to be attainable on a five-year timescale in view of some new developments and the foreseeable progress. Finally, a possible simple new definition of the kelvin is proposed.

We study the adsorption and wetting behaviour of colloidal hard spheres and colloidal rod-like particles at a planar hard wall using computer simulations. Our results show complete wetting by the hard-sphere crystal at the wall–fluid interface, and complete wetting by the nematic phase of the hard-rod fluid at the wall–isotropic fluid interface. In addition, we investigated the effect of polymer-mediated effective interactions on the wetting behaviour of colloidal spheres. The many-body character of the effective colloidal interactions yields an adsorption behaviour that differs enormously from those found for pairwise simple fluids; e.g., far from the triple point, we find three layering transitions in the partial wetting regime prior to a transition to complete wetting by the colloidal liquid.

The defining fixed points of the International Temperature Scale of 1990 (ITS-90) are temperature reference points for temperature calibration. The measured temperature inside the fixed-point cell depends on thermometer immersion, since measurements are made below the surface of the fixed-point material and the additional effect of the hydrostatic pressure has to be taken into account. Also, the heat flux along the thermometer stem can affect the measured temperature. The paper presents a system that enables accurate and reproducible immersion profile measurements for evaluation of measurement sensitivity and adequacy of thermometer immersion. It makes immersion profile measurements possible, where a great number of repetitions and long measurement periods are required, and reduces the workload on the user for performing such measurements. The system is flexible and portable and was developed for application to existing equipment in the laboratory. Results of immersion profile measurements in a triple point of water fixed-point cell are presented.

The properties of pyridinium perrhenate have been studied by three methods: dielectric spectroscopy, neutron powder diffractometry and NMR spectrometry under high pressure. It has been shown that under high pressure the temperatures of the two phase transitions in the crystal are shifted towards lower ones. Moreover, the results have shown the occurrence of a new high pressure phase with a triple point corresponding to the pressure of 100 MPa and the temperature of 240 K.

A study is made of an anisotropic Potts model in three dimensions where the coupling depends on both the Potts state on each site but also the direction of the bond between them using both analytical and numerical methods. The phase diagram is mapped out for all values of the exchange interactions. Six distinct phases are identified. Monte Carlo simulations have been used to obtain the order parameter and the values for the energy and entropy in the ground state and also the transition temperatures. Excellent agreement is found between the simulated and analytic results. We find one region where there are two phase transitions with the lines meeting in a triple point. The orbital ordering that occurs in $LaMnO_3$ occurs as one of the ordered phases., 30 pages, 19 figures, one table

The EPR spectra of BaTiO3+0.04 BaO +0.01 Cr2O3 ceramics are studied in three frequency bands (9, 34 and 94 GHz). Three different, axially symmetric EPR spectra assigned to Cr3+ ions substituted at Ti sites corresponding to the different distorted octahedra in tetragonal and hexagonal crystal surroundings are observed at room temperature. The temperature dependence of the EPR spectra allowed the unambiguous assignment of the chromium ions to the lattice site in tetragonal and hexagonal modifications. The concentration measurements revealed that only 30% of the chromium is incorporated in the grains as Cr3+ ions whereas the remnant is in the EPR-silent tetravalent charge state or in Cr-rich secondary phases segregated at grain boundaries, pores and triple points. The intensity ratio of the two Cr3+ spectra in hexagonal BaTiO3 depends on the preparation conditions.

Triple-point wetting is a well-known phenomenon of simple adsorbates on solid substrates, which involves, in the liquid phase above the triple-point temperature, T3, complete wetting with the formation of arbitrary thick films being observed, whereas below T3 only a few monolayers of the solid phase are adsorbed at saturated vapour pressure. This effect is usually ascribed to the substrate-induced strain in the solid film, which occurs due to the lattice mismatch and the strong van der Waals pressure in the first few monolayers. Molecular hydrogen is a suitable system in which to investigate this phenomenon, in particular by tailoring the adsorbate substrate interaction by means of thin preplating layers of other adsorbates, and by introducing disorder into the system by using not only the pure systems H2 and D2, but also mixtures thereof. The experiments show that triple-point wetting is a rather dominant effect which, in contrast to expectations, persists even if the system parameters are widely varied. This indicates that the present understanding of this effect is incomplete. We present an investigation of the influence of the roughness of the substrate which is expected to be responsible for the dewetting of the solid phase.

NH--N hydrogen bonded ferroelectric dabcoHBF4, [C6H13N2]+BF4−, has been studied by dielectric spectroscopy, differential thermal analysis and pyroelectric charge measurement investigations in the low-temperature range between 12 and 300 K, and at elevated hydrostatic pressures up to 1 GPa. The p–T phase diagram has been determined and described. In addition to the known first-order phase transitions at 378 and 153 K, two new structural transitions of continuous type have been revealed, i.e., the transition at 37 K and the pressure-induced one occurring above the triple point situated at 80 MPa and 165 K. Both of these transitions have essentially displacive character and a mechanism related to distortions of the hydrogen bonded polycationic chains, preserving polar properties of the crystal. The possible order–disorder contribution to the transition at 153 K between the ferroelectric phases II and III is discussed in relation to the conformational properties of the dabco cation.

We have measured the differences between the Kelvin thermodynamic temperature and the temperature of the International Temperature Scale of 1990 on nine isotherms between the triple point of mercury and 380 K, by means of a primary acoustic thermometer. For the present measurements the standard uncertainty of (T − T90) ranges from 0.9 mK at 234 K to 1.7 mK at 380 K. The experimental method is based on the measurement of the acoustic resonance frequencies of an argon-filled spherical cavity and the microwave resonance frequencies of the same cavity when evacuated. The present results agree within the remarkably small combined uncertainties with both NIST acoustic thermometry ([1] Moldover M R et al 1999 J. Res. Natl Inst. Stand. Technol. 104 11–46; [2] Strouse G F et al 2002 Progress in primary acoustic thermometry at NIST: 273 K to 505 K 8th Temperature Symp. (Chicago, 21–24 October 2002)) and UCL acoustic thermometry ([3] Ewing M B and Trusler J P M 2000 J. Chem. Thermodyn. 32 1229–55) in the overlapping temperature range.

The metastable phase equilibria of substances in the disordered, liquid or amorphous, state are considered in T–P coordinates. Application of the thermodynamic model of pseudo-binary solutions is illustrated by means of calculated metastable T–P phase diagrams of water, carbon, and semiconducting compounds, GaSb and Ga38Sb38Ge24. All calculated diagrams include the equilibrium lines between the disordered phases terminating at the critical points and the stability boundaries of these phases, the spinodals. Depending on the mutual disposition of the elements of the stable and metastable T–P diagrams, two additional lines of metastable equilibria between the crystalline high-pressure phase and each of the metastable disordered phases can appear. These lines terminate at the points of intersection with spinodals. These special points are denoted as pseudo-critical points. A combined analysis of the stable and metastable diagrams gives a reasonable interpretation of the experimental data on the phase transformations and on the nature of the anomalous properties of the substances in question as well as allowing prediction of some new effects.

It is by now well established that the self-consistent Ornstein-Zernike approximation (SCOZA) is able to provide accurate data for the location of the liquid-vapour coexistence curve and for the critical point of simple fluids. However, up to now applications of the SCOZA were restricted only to a rather small variety of interatomic potentials. In this contribution we present an extension of the SCOZA which offers access to a considerably larger class of systems. As an example, we present results for model fullerenes Cn ≥ 60 (characterised by the sphericalized Girifalco potentials) and thus contribute to the still open question on the existence of the liquid phase and on the size of the liquid pocket in the phase diagram of fullerenes.

We investigate the behavior of a model colloidal mixture of hard spheres and rod-like particles near a planar hard wall using density functional theory. For small size ratios of rod length and sphere diameter we find that the colloidal liquid phase wets the wall completely upon approaching the fluid demixing binodal from the colloidal gas side, provided the density of the rods lies below the wetting point. Using an effective one-component description based on the pairwise depletion potential for higher density of rods, a finite sequence of layering phase transitions is found. For large rod-to-sphere size ratios, using a binary treatment, thick films are obtained even close to the triple point.

The phase behaviour of Ar and Kr adsorbed in Vycor glass at pressures and temperatures above the bulk triple point and below the bulk critical point has been investigated. Ar is found to condense in the pores ~2 K above the bulk transition and freeze ~10 K below the bulk transition. In contrast the condensation transition for Kr is shifted up by 4 K and freezing shifted down by 15 K. There is a pronounced hysteresis (4–6 K) at the liquid/solid phase boundary and a lesser amount (~2 K) at the gas/liquid boundary. We find clear differences between the pore filling and emptying processes at the gas/liquid phase boundary and evidence of pore blocking on desorption. In addition microbubbles or large gas–liquid interfaces are thought to occur when Kr condenses in the pores but this effect is absent in Ar. Finally, solid Ar in the pores melts in a more continuous way than Kr.