Rhodium-iron Resistance Thermometers Research Articles

Measurement of thermodynamic temperature between 5 K and 24.5 K with single-pressure refractive-index gas thermometry

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.

Tests of the Stability of Chinese RhFe Resistance Thermometers at Low Temperatures

Rhodium–iron resistance thermometers are recommended as precise thermometers at temperatures below 25 K. The thermometers were developed at the National Physical Laboratory and produced by H. Tinsley and Co Ltd almost 50 years ago. Later, they were made by other companies and institutes as well, but despite this, the availability of the thermometers decreased and a new source of supply was needed. Several years ago, the Technical Institute of Physics and Chemistry (TIPC), Chinese Academy of Sciences, developed its own technology for making wire of Rh-0.5 at% Fe alloy which was used in the production of new thermometers. These devices have been tested previously at INRIM (Italy) and later at INTiBS (Poland). INTiBS has carried out an investigation focused on the thermometers’ stability after thermal cycling treatment. This paper presents the results of stability tests of about 30 thermometers produced by TIPC in two batches. The resistance of each thermometer was measured at temperatures of about 4.6 K and 7.2 K before and after 10, 30 and 50 thermal cycles from room temperature. The methods of measurement and the design of the cryostat used for the research are also presented.

EURAMET key comparison no. EURAMET.T-K1: realisations of the ITS-90 from 2.6 K to 24.5561 K, using rhodium-iron resistance thermometers

In the temperature range from 0.65 K to 24.5561 K, the ITS-90 is defined by specified vapour-pressure equations for 3He and 4He and interpolation equations for a constant-volume gas thermometer using 3He or 4He. The definitions are given in sections 3.1 and 3.2 of the ITS-90 text, and methods for realising the scale in this range are outlined in chapters 4 and 5 of the Guide to the Realization of the ITS-90 (formerly Supplementary Information for the ITS-90). Direct realisations of the ITS-90 by these methods require relatively sophisticated apparatus and time-consuming experiments, and consequently they are rarely carried out. The situation is acceptable in practice only because rhodium-iron resistance thermometers (RIRTs) are available that, once calibrated, are able to maintain their calibrations reliably for long periods of time. They are the practical thermometers on which realisations of the ITS-90 are most accurately maintained, disseminated and compared. The key comparison EURAMET.T-K1 is therefore a comparison of calibrated RIRTs.Main textTo 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).

Development of Chinese Standard Type of Rhodium-Iron Resistance Thermometer

New rhodium alloy wires with 0.52 % atomic of iron have been drawn, and several batches of RhFe thermometer with strain-free construction and helium-filled platinum capsule have been made using these new alloy wires and old alloy wires which were made in the 1980s in China. In one of the constructions, the coil of wire is inserted into twisted glass tubes, and in the other, it is laid in grooves on a fused-silica crossed frame. The resistance versus temperature relationship and interpolating characteristic of Chinese RhFe thermometer are similar to those of Tinsley 5187U thermometer from 1.5 K to 27 K. The resistance changes of most thermometers are less than that of equivalent to 0.2 mK at 4.5 K after they are exposed to fifty thermal cycles from room temperature to liquid helium temperature. This standard type of rhodium-iron resistance thermometer is now commercially available. Instead of the regular annealing temperature, which is $$750\,^{\circ }$$ C, two batches of RhFe thermometers are made with the annealing temperature of $$850\,^{\circ }$$ C and $$950\,^{\circ }$$ C. The interpolating characteristics of RhFe thermometers will be studied to find new calibration method.

A Standardized Interpolation of Temperature Using Rhodium–Iron Resistance Thermometers Over the Interval 4.2 K to 24.5 K

The worldwide history and present state of development of rhodium–iron resistance thermometers (RIRTs) is briefly reviewed. A standardized interpolation method using RIRTs with the nominal composition of 0.5 % Fe (by mole) is presented, with examples using data taken from 60 RIRTs made from a variety of wire batches and sources worldwide over the last 40 years. The parameterization exploits the favorable characteristics of the Cragoe reduced resistance $$Z(\tau )$$ and a suitably reduced temperature $$\tau $$ . A reference function $$Z_\mathrm{ref}(\tau )$$ which approximates the average characteristics of selected wire is derived for use over the interval 0.65 K to 24.5561 K on the ITS-90. The deviations of real RIRT data from this reference function are examined, and simple four-parameter Fourier-series solutions for the resulting deviation curves are presented. Despite the fact that the wire samples may be of different origins or state-of-anneal, it was found that the interpolations are successful for most of the samples studied over the 4.2 K to 24.5561 K interval, at the level of $$\approx $$ 1 $$\hbox {mK}$$ standard uncertainty or less. This method would allow for calibrations of most RIRTs over this interval using only six calibration points, permitting an efficiency not achievable using the common least-squares curve-fitting calibration methods. The potential of this formalism for a standardized interpolation scheme using RIRTs is discussed.

$$^{3}$$ 3 He Interpolation Gas Thermometry with Different Virial Coefficients and Gas Densities and Model Calculation of a Temperature Profile with Radiative Heat Transfer

\(^{3}\)He interpolating constant-volume gas thermometer scales are compared using different virial coefficients and gas densities for a temperature range of 3 K to the triple point of Ne (24.5561 K). The differences between the International Temperature Scale of 1990 (ITS-90) and the interpolation scale, which follows the definition of the ITS-90 but uses the second and third virial coefficients of the recent ab initio calculations, have maxima of about 0.08 mK and 0.13 mK for gas densities of \(168\,\hbox {mol}{\cdot }\hbox {m}^{-3}\) and \(278\,\hbox {mol}{\cdot }\hbox {m}^{-3}\), respectively. The differences between the ITS-90 and the interpolation scale using only the ab initio second virial coefficient have maxima of about 0.08 mK and 0.14 mK for the same respective sequence of gas densities. The ITS-90 temperatures obtained in eight runs with gas densities from \(127\,\hbox {mol}{\cdot } \hbox {m}^{-3}\) to \(278\,\hbox {mol}{\cdot }\hbox {m}^{-3}\) agree with a polynomial of the resistance of a rhodium–iron resistance thermometer within 0.2 mK. To calculate the temperature profile along the pressure-sensing tube connecting the low temperature part of the constant-volume gas thermometer to room temperature, a calculation model is proposed that takes into account not only the thermal conductivity of the tube wall but also the radiative heat transfer between the tube and the vacuum jacket enclosing it. The calculation results of this model approximate the measured profile better than the conventional calculations that neglect the radiative heat transfer.

Study of the reference standard facility of rhodium-iron resistance thermometer

A 704 type 4He cryostat is designed and the “National (China) Temperature Working Standard Group of the ITS-90 at 1.2–24 K” have been composed. A 703 type 3He cryostat have been established and the working temperature of the “National Temperature Working Standard Group of the ITS-90 at 1.2–24 K” is extended to 0.65 K, which is the lowest limit temperature of ITS-90. The 5 rhodium-iron resistance thermometers (RIRTs) which compose the Working Standard Group have been transformed to the International Temperature Scale of 1990 (ITS-90). A set of indexing data is fitted and calculated as the indexing table of the standard facility of RIRT. 42 basis temperature points have been measured at 0.67–26.37 K. The results show that the temperature control level could reach 0.5 mK/30 min. The difference between the temperature value of the 5 RIRTs and the average is less than 1.1 mK, and the comparison measurements uncertainty is 0.95 mK.

Analysis of the Factors Affecting the Realization of Lambda Transition Temperature of 4He

Analysis of the Factors Affecting the Realization of Lambda Transition Temperature of 4He Owing to the dramatic change in the thermal conductivity of 4He when its temperature crosses the transition of superfluid (HeI) and normalfluid (HeII), a sealed-cell with a capillary is used to realize the lambda transition temperature, Tλ. A small heat flow is controlled through the capillary of the sealed-cell so as to realize the coexistence of HeI and HeII and maintain the stay of HeI/HeII interface in the capillary. A stable and flat lambda transition temperature "plateau" is obtained. Because there is a depression effect of Tλ caused by the heat flow through the capillary, a series of heat flows and several temperature plateaus are made and an extrapolation is applied to determine Tλ with zero heat flow. A rhodium-iron resistance thermometer with series number A34 (RIRT A34) has been used in 24 Tλ -realization experiments to derive Tλ with a standard deviation of 0.022mK, which proves the stability and reproducibility of Tλ.

An Adiabatic Calorimeter for the Realization of the ITS-90 in the Cryogenic Range at the LNE-CNAM

The LNE-CNAM, in cooperation with the IPN, has recently developed a new cryogen-free adiabatic calorimeter, to realize the International Temperature Scale of 1990 (ITS-90) in the temperature range between 6 K and 84 K. The new calorimeter, cooled by a closed-cycle Gifford-McMahon refrigerator, is equipped with three thermal shields and two separate vacuum chambers, to minimize the effect of parasitic heat fluxes. The inner adiabatic chamber can accommodate either a multi-compartment cell—containing the triple points of hydrogen, neon, oxygen, and argon, to realize the ITS-90 between 14 K and 84 K—or a comparison block for thermometers, the calibration of rhodium–iron (RhFe) thermometers between 6 K and 24 K. The use of a cryogen-free system and a fully computer-controlled measurement chain allow long lasting experiments and good thermal control, resulting in a substantial reduction of the measurement uncertainties. The new adiabatic calorimeter has been successfully tested at the LNE-CNAM. The overall standard uncertainties in the realization of the ITS-90 have been reduced from 2.08 mK to 0.37 mK at the hydrogen triple point, from 1.40 mK to 0.30 mK at the triple point of neon, and are maintained below 0.26 mK at the triple points of oxygen and argon. In the temperature range between 6 K and 24 K, calibrations of rhodium–iron resistance thermometers have been carried out with a standard uncertainty of the order of 0.80 mK.

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.

Final Report on CCT-K1: Realizations of the ITS-90, 0.65 K to 24.5561 K, using rhodium–iron resistance thermometers

In 1996 the CCT initiated five key comparisons of realisations of the ITS-90 in various parts of the range. CCT-K1 concerns the range 0.65 K to 24.5561 K, where the ITS-90 is defined by specified vapour-pressure equations for 3He (0.65 K to 3.2 K) and 4He (1.25 K to 5.0 K) and by interpolation equations for a constant-volume gas thermometer (3 K to 24.5561 K). The transfer standards were rhodium–iron resistance thermometers calibrated by the seven participating laboratories. The report describes the comparison experiments, the results and uncertainties, and the calculation of interlaboratory equivalences. The comparison has been concluded by preparing an entry for Appendix B of the BIPM Key Comparison Database.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 (MRA).

The properties of Chinese standard rhodium-iron resistance thermometers

The stability of eleven standard-type rhodium-iron resistance thermometers of Chinese manufacture has been studied while they were exposed to 30 thermal cycles between 293 and 4.2 K. Over these cycles, seven of the eleven thermometers remained stable at 24.5 K within the 0.1 mK precision of the measurements. Two of the thermometers exhibited unstable behaviour at the 10 mK level. The characteristic resistance versus temperature behaviour of, and the self-heating effect in, the other nine thermometers, together with that of two other thermometers of the same type, have been studied in the temperature range 1.3-27 K. The Chinese thermometers appear to be similar in behaviour to the more familiar rhodium-iron thermometers manufactured by H. Tinsley and Co. Ltd.

Rhodium-iron resistance thermometer with fused-silica coil frame

The dependences of the thermometric properties of a rhodium - iron (RhFe) (mole fraction 0.5%) wire resistance thermometer on the annealing temperature between 700 and 900°C are investigated using fused-silica coil frames. The thermometers annealed at or above 800°C have similar temperature - resistance characteristics. These thermometers can be calibrated with an accuracy of 0.5 mK over the range 4.2–25 K using a reference temperature - resistance function and three calibration points. RhFe wire thermometers from different origins can be calibrated with an accuracy of the order of 10 mK in the same way. The temperature rise of the present thermometers due to heating by the measuring current is in a reasonable range for thermometry with a millikelvin accuracy.

The characteristics of Chinese encapsulated rhodium-iron resistance thermometers

The resistance-temperature characteristics, self-heating effect and stability of a new type of Chinese encapsulated rhodium-iron resistance thermometer have been studied in the temperature range between 1.2 and 273.15 K. Resistance changes at 20 K in ten such thermometers over 30 thermal cycles between 15 and 290 K were equivalent to temperature changes of between 30 and 70 mK. The resistance against temperature characteristics of the thermometers are similar to those of standard Rh-Fe resistance thermometers and the thermometers' interchangeability characteristics are such that a one-point (273.15 K) calibration delivers a precision of 0.2 K in temperature over the range 1.2 to 273.15 K while a three-point (4.2, 77 and 273.15 K) calibration gives a precision of 22 mK below 77 K and 15 mK above 77 K.

Cryogenic Temperature Measurement

Applications of the rhodium-iron resistance thermometer over the last two decades have demonstrated that this sensor has the widest temperature range known; it has been used between 0.01 and 800 K, nearly five orders of magnitude. Recent developments have resulted in the production of a small planar device, which is finding many uses in cryogenic instrumentation.

Constant-Volume Gas Thermometry Between 4 K and 100 K

Gas-thermometer measurements between 4 K and 100 K have been performed at the Kamerlingh Onnes Laboratory as part of the preparatory work in several institutes for a future, revised, International Practical Temperature Scale. Gas-thermometer temperatures are compared, between 13.8 K and 100 K, with platinum resistance thermometers calibrated on IPTS-68 and, between 4.2 K and 27.1 K, with rhodium-iron resistance thermometers calibrated on the National Physical Laboratory (Teddington) Scale of 1975 (NPL-75).Results of the measurements, with NPL-75 at 20.3 K as a reference temperature for the gas thermometer, show agreement with NPL-75 within 0.3 mK over most of the range. Differences from NPL-75 of 0.6 mK were found in the range 10 K to 14 K and around 27 K.Below 50 K, IPTS-68 is shown to be 4 mK to 10 mK higher than thermodynamic temperatures. Between 70 K and 100 K, IPTS-68 is 9 mK lower than thermodynamic temperatures.

Stability characteristics of rhodium-iron alloy resistance thermometers

The stability of nine precision rhodium-iron alloy resistance thermometers has been studied over 11 weeks while they were exposed to repeated thermal cycling between 293K and 6K. With one exception, the thermometers were completely stable at both 90K and 6K within the 0.05 mK precision of the measurements. The one thermometer which lacked stability did so by only 0.07 mK at 6K and 1 mK at 90K.

A New Determination of the Helium Vapour Pressure Scales Using a CMN Magnetic Thermometer and the NPL-75 Gas Thermometer Scale

A single-crystal cerous magnesium nitrate (CMN) paramagnetic salt thermometer has been set up and used for therometry between 0.4 K and 3.1 K in a cryostat also equipped for the measurement of the vapour pressures of 3He and 4He. Two temperature scales, TX 1 and TX 2, have been derived in experiments with samples of CMN obtained from different sources. They are in agreement to ± 0.2 mK with the NPL-75 gas thermometry scale above 2.6 K, with the TXISU (1975) magnetic thermometry scale down to 1.3 K and with each other down to 1 K. There are appreciable differences between the two scales below 1 K for an unidentified reason. The scales are retained in terms of calibrations of 5 rhodium-iron resistance thermometers which also carry NPL-75. Vapour pressure data for 3He and 4He obtained with these thermometers have contributed to the derivation of values for the differences between EPT-76 and the established vapour pressure scales, T58 and T62, and also are intended for use in the complete revision of T58 and T62 which is envisaged by the Comité Consultatif de Thermometrie. The relationships between these various scales and other thermometric data in the range 0.5 K to 5.2 K are discussed.