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In the cryogenic temperature range between 13.8033 K and 273.16 K, eight fixed points are required by the International Temperature Scale of 1990 (ITS-90 or T90) to fully calibrate a standard platinum resistance thermometer (SPRT). Two of them are often no longer realized according to the prescriptions defined in the scale but by comparison with a "wire scale": they are the two temperatures close to 17 K and 20.3 K. On the other hand, some primary methods, such as acoustic gas thermometry (AGT), are now able to measure any thermodynamic temperature T in this range with user-adjustable spacings. We investigate here the suitability of "hybrid" calculations for the temperature with an SPRT carrying both ITS-90 and AGT calibrations. The ITS-90 equations are applied to a modified fixed-point set, where the two mentioned ITS-90 points are replaced by (alternative) thermodynamic temperatures close to those of the original fixed-points. Several AGT points are tested as possible replacements, by substituting them in the calculation procedure of the calibration coefficients. The results consider different scenarios, where only one or both ITS-90 points are replaced, to find the optimal combination for the difference T - T90 with the lowest uncertainty. [ABSTRACT FROM AUTHOR]

The International Temperature Scale of 1990 (ITS-90) has successfully underpinned thermometry worldwide for more than three decades. But times are changing. Primary thermometry technology has improved and continues to advance. The Consultative Committee for Thermometry (CCT) has encouraged National Metrology Institutes (NMIs) to directly disseminate thermodynamic temperature T according to the new definition of the kelvin. The CCT has also published a mise en pratique containing endorsed methods of doing so. It anticipates that T dissemination will gradually replace ITS-90 temperature T90 dissemination. But the path from universal T90 dissemination to universal T dissemination will be long and difficult, especially in the important middle part of the scale. Under the guidance of the CCT, some NMIs will begin to offer T calibrations, while many others continue to disseminate T90. Thermometers carrying T calibrations will coexist with those carrying T90 calibrations out in the world. This global Mixed Dissemination Environment (MDE) will fluctuate over many decades as different primary thermometry capabilities come online and evolve. The problem for users is that T and T90 are not equivalent: the difference between them is more than 10 times larger than ITS-90 calibration uncertainties over most of the long-stem standard platinum resistance thermometer (LSPRT) range. In the MDE, even users unconcerned with thermodynamic accuracy will need to keep track of which thermometers give T and which give T90, as these change over time in a patchwork fashion. This paper explores the future of the International Temperature Scale in the context of the coming MDE. It proposes simplifying the disjointed T90 to T transition by introducing a new temperature scale (ITS-XX) with temperatures TXX that are equal to T within uncertainties. NMIs everywhere could implement the new scale on day one with existing equipment by updating tables of SPRT reference function coefficients and fixed point values. Then further moves to direct T dissemination by individual NMIs would be transparent to the users. Concerns about tightening mercury regulations would also be resolved and scale realization uncertainties reduced. A new scale would be costly to adopt, but the minimal ITS-XX variant proposed here represents the path of least net disruption through the coming MDE. These changes could be implemented in the next 10 years, transforming the ITS-90 into the accurate, reproducible, flexible scale its creators intended to make in the first place. [ABSTRACT FROM AUTHOR]

In contact thermometry calibration of resistive probes, there are a number of factors which cause measurement uncertainty. Among these are measurement noise and repeatability, uncertainty due to the measurement readout, true temperature of the heat source, immersion effects, and self-heating. Both immersion effects (sometimes referred to as stem effect) and self-heating can be influenced by a number of factors. The obvious factors include thermal conduction of the probe's stem, immersion depth of the probe into the heat source medium, excitation current, and probe resistance. These factors are all directly related to the probe itself. There are other factors related to heat transfer between the probe and the heat source medium that affect both immersion effects and self-heating. These are mainly due to the convective or conductive heat transfer between the probe and the heat source. These will change with temperature, the heat source medium used, and if a stirred liquid medium is used, it will also change based on the stirring velocity of the bath fluid. This paper covers a few basic concepts and terms related to a resistive temperature probe calibration. It speaks to the basics of heat transfer in a temperature probe calibration. It then discusses the results of an immersion effect and self-heating study. The study is based on data in different heat sources including stirred liquid baths, a fixed-point, and a dry-block calibrator. The paper discusses the results and speaks to how results of such tests may be interpreted by the user. [ABSTRACT FROM AUTHOR]

The mise-en-pratique for the definition of the kelvin has given the possibility of relative primary thermometry with uncertainties competitive with the ITS-90 above the silver freezing point. The mise-en-pratique does not constrain users to any particular experimental method to realise the kelvin, so while there is supporting documentation it may not be obvious to everyone how to actually establish SI traceable temperatures. NPL has established thermodynamic temperature above the silver point using high-temperature fixed-points. This approach provides access to thermodynamic temperature with lower uncertainties than can be routinely achieved through absolute primary radiometry. We demonstrate direct traceability to the kelvin and that this is more easily and robustly achieved than its equivalent ITS-90 approximation. [ABSTRACT FROM AUTHOR]

With the redefinition of the kelvin in 2019 and the new mise en pratique for the definition of the kelvin (MeP-K) [1], the realization of the kelvin is no longer exclusively confined to the International Temperature Scales (ITS-90, PLTS-2000). Primary thermometry has become possible as an alternative method for the realization of the kelvin. For that purpose, different primary thermometers, specifically the primary magnetic field fluctuation thermometer (pMFFT), the Coulomb blockade thermometer (CBT) and the acoustic gas thermometer (AGT) have been optimized in the EMPIR project Real-K [2] for an extended operation range to cover, at least partly, the temperature range from 1 K to 25 K. The performance of the thermometers was checked by comparison with the ITS-90 at various arbitrary temperatures. Two reference points served as highly stable and well characterized references, the superfluid lambda transition in 4He (λ-point) at 2.1768 K and the Ne triple point at 24.5561 K. With pMFFT and CBT we also demonstrated a smooth overlap between the PLTS-2000 range below 1 K and the ITS-90 range above 1 K. All the investigated primary thermometers proved to be very practical alternatives to the established thermometric methods of the ITS-90 in the range below 25 K. [ABSTRACT FROM AUTHOR]

Since 1997, the Thermometry Laboratory (Later) of Inmetro has taken part in several comparisons of ITS-90 temperature standards to establish the traceability of the laboratory's SPRT calibrations. More recently, Inmetro took part in the key comparison CCT-K9, which has just been published, with very positive results. Over these 25 years, however, different standards were either purchased or developed, and some unfortunately failed or broke, so fixed-point cells were not the same across comparisons, which turns the task of keeping the ITS-90 traceability chain challenging. Here we present a study that consolidates the results of all SPRT comparisons at Later/Inmetro since 1997, demonstrating that Inmetro's ITS- 90 traceability has been successfully maintained for more than two decades. By linking the results of different comparisons, we were able to determine the temperature differences and uncertainties of the fixed-point cells ranging from the triple point of argon (Ar, -189.3442 °C) and the freezing point of zinc (Zn, 419.527 °C), and to estimate what would have been Inmetro's results if the current reference standards had been used in the previous comparisons. [ABSTRACT FROM AUTHOR]

The redefinition of the kelvin is introduced followed by an overview of progress made towards realizing the redefined kelvin with particular emphasis on using primary thermometry approaches to enable traceability direct to the kelvin definition. Perspectives for temperature traceability in the short-, medium- and long-term are discussed along with the possible requirements for a future temperature scale. [ABSTRACT FROM AUTHOR]

The current International Temperature Scale of 1990 (ITS-90) is the fundamental scale for temperature measurement worldwide. The instrumentation involved includes reference artefacts such as fixed points based on phase transitions of pure materials to calibrate the thermometers specified in [1]. The temperatures assigned to the fixed points on the ITS-90 were based on measurements made using the best determinations of thermodynamic temperature and several measurements have highlighted small departures of the ITS-90 from thermodynamic temperature across the range from 20 K to 1235 K [2], with the uncertainty in the difference being especially large above the Zn point (about 693 K). This paper describes the assignment of the thermodynamic temperature of an Al fixed point (ITS-90 values: 933,473 K, 660,323 °C) using relative and absolute primary radiation thermometry. [ABSTRACT FROM AUTHOR]

The International Temperature Scale of 1990 defines the temperature in the range between 0.65 K and 5.0 K in terms of the vapor pressure of the two isotopes of helium3He and 4He. The 3He isotope is used between 0.65 K and 3.2 K, and the 4He isotope is employed in the range from 1.25 K to 5.0 K. LNE-Cnam has developed an apparatus for vapor pressure thermometry with two separate gas systems installed in the same cryostat. One is dedicated to 3He and the other to 4He. Each one is equipped with its own vapor-pressure chamber, to avoid any mixing and preserve the purity of the two gases. The two chambers are within the same copper block to ensure their temperature equality. The apparatus is cooled by a commercial dilution refrigerator [1]. The setup allows the simultaneous realization of the two temperature definitions, the one based on 3He and that based on 4He, and therefore a direct comparison, without any transfer standard. In this paper we present a comparison of the two temperature definitions, carried out between 2.1 K and 3.1 K. [ABSTRACT FROM AUTHOR]

In 2011, a working group of the Consultative Committee for Thermometry published their best estimates of the differences between the thermodynamic temperature T and its approximation (T90), the temperature according to the International Temperature Scale of 1990, ITS-90. Since 2011, there has been a change in the definition of the kelvin and significant improvements in primary thermometry. A recent paper [J. Phys. Chem. Ref. Data 51, 043105 (2022)] updates the (T - T90) estimates by combining and analyzing the old and new data. The new data has been obtained by four types of gas thermometry. Their uncertainty estimates are now comparable with the uncertainties in the best measurements of T and the uncertainties in ITS-90 realizations. The new estimates are the basis for updating the annex Estimates of the differences T – T90 of the Mise en pratique for the definition of the kelvin in the SI. For users without primary thermometry capability, it is now possible to access thermodynamic temperature values T below 335 K with comparably small uncertainties via an ITS-90 calibration and the transfer applying (T - T90). This is a way to bridge the existing gap between enormous effort for T measurements and comparably good access to T90. The applications in this way are divers and increase with demands for decreasing uncertainties. Three examples are treated in this paper in different fields, such as (1) alternative pressure standard applying invers dielectric-constant gas thermometry, (2) thermophysical properties, where ab initio calculations of gas properties have made enormous progress, and (3) optical clocks. [ABSTRACT FROM AUTHOR]

The paper considers laboratory experiments on unilateral freezing of samples of dry and wet sand. Freezing was carried out in the refrigerator under the influence of a cooling thermal plate from above. Thermometry of frozen sand samples was performed. As a result, the propagation velocity of the cold wave in the samples, the movement of the freezing front and the duration of the phase transition are estimated. Mathematical modeling of the sample cooling process was also performed. [ABSTRACT FROM AUTHOR]

The purpose of the study is to develop and test a hardware-software complex for contactless temperature change. The research methodology is the use of double measurement of thermal radiation from the skin surface (on the face and on the wrist). Methods of descriptive statistics and Irwin's criterion were used to process the test results. In the study, a software and hardware complex for contactless thermometry of people entering the building was created and tested, its schematic diagram is presented, and algorithms of operation are described. The function describing the dependence of skin temperature on infrared energy has been clarified. The problem of the deviation of the skin surface temperature from the temperature in the armpit is considered and it is proposed to use Irwin's criterion to separate the increased values from the normal ones. The testing of the hardware and software complex in a study involving 113 participants showed that it can reliably identify persons with fever. All 11 people with an armpit temperature of more than 37.1 ◦C had abnormally high skin surface temperatures according to Irwin's criterion. The absence of false positive and false negative results was confirmed by traditional thermometry. [ABSTRACT FROM AUTHOR]

The paper considers the possibility of using quartz sensing elements for the development of cryogenic temperature sensors. The main criteria for the development of cryogenic thermometry are: increasing the sensitivity and stability of the metrological characteristics of the sensors, reducing the design parameters and expanding the operational characteristics of the sensors, since they are the main elements of the schemes ensuring the operation of cryogenic thermostating systems. [ABSTRACT FROM AUTHOR]

A possibility to use competing effects of deep traps in anion-defective alumina single crystals for luminescent thermometry was studied. The proposed method is based on measuring changes in TL intensity of the main peak at 180 °C when the state of the occupancy of deep traps, which are emptied at 300-900 °C, varies. It was found that the temperature can be changed with the reported method in the range of T=600-900 °C when the deep traps are filled with UV-radiation, and at T=350-500 °C when the traps are filled with a pulse electron beam. The sensitivity of the method under discussion to temperature proved to be comparable with the sensitivity of other luminescent methods of thermometry. [ABSTRACT FROM AUTHOR]

In the Magnetic Hyperthermia - the control of the temperature field within the malignant tissues is an important task which receives a considerable attention in the all experimental and theoretical researches. A temperature analysis focus the main parameters which influences strongly this therapy. The spatial distribution of the particles influences significantly the temperature field developed within a malignant tissue, when an external time - dependent magnetic field is applied. This paper analyses the temperature field induced by the particulate systems (magnetite and maghemite) with an exponential spatial distribution within a concentric tissues configuration (malignant and healthy tissues). The temperature field developed by these magnetic systems was computed using an analytical model which predicts the temperature at every point. This model was developed in order to compute the isothermal surfaces in the range of the therapeutic temperature range: 42-46°C . The parameters involved in the burning process of the malignant tissues are optimized to get the uniform hyperthermic temperatures within malignant tissues for a corresponding clinically particle dosage. [ABSTRACT FROM AUTHOR]

Non-invasive tissue temperature estimation is important in thermal therapies for having an efficient treatment. A noninvasive ultrasonic technique for monitoring tissue temperature changes is proposed based on the changes in the harmonics of ultrasound backscatter as a function of temperature. The backscattered pressure amplitudes of the fundamental frequency (p1), the second (p2) and the third (p3) harmonics generated by nonlinear ultrasound propagation and the ratios of the second and the third harmonics over the fundamental frequency (p2/p1 and p3/p1) were investigated as a function of temperature. The acoustic harmonics were generated and detected with a commercial high frequency ultrasound imaging system in pulse-echo mode. The experiments were performed on tissue-mimicking gel phantoms and ex vivo bovine muscle tissues. The temperature was increased from 26°C to 46°C in increments of 2°C. The average values of p1, p2, p3, p2/p1, p3/p1 increased by 14%, 50%, 117%, 37% and 92% for the gel phantoms, and for the tissue samples increased by 29%, 50%, 170%, 10% and 109%, respectively. The results indicate that the harmonic amplitudes and their ratios are highly sensitive to propagation medium's temperature and could potentially be used for noninvasive ultrasound thermometry. [ABSTRACT FROM AUTHOR]

In this study, we have implemented T2-based monitoring of near-field heating in patients undergoing HIFU ablation of uterine fibroids using Insightec ExAblate system. In certain areas, near-field heating can reach 18°C and the tissue may experience sustained heating of more than 10°C for the period of 2 hours or more. This indicates a cumulative thermal dose that may cause necrosis. Our results show the feasibility and importance of measuring near-field heating in subcutaneous fat. [ABSTRACT FROM AUTHOR]

Proton resonance frequency (PRF) change is used to measure tissue heating, but also distorts the image and causes geometric distortions in temperature estimates in the same manner as other chemical shift distortions if left uncompensated. We propose an algorithm that produces PRF temperature maps free of these distortions by fitting a signal model directly to acquired k-space data that accounts for PRF-induced phase both up to and during the readout. We also introduce a faster method compatible with Cartesian data that corrects distortions from image-domain temperature maps.Gel heating experiments show the proposed CS compensation algorithms correct magnitude image artifacts and hotspot distortions. Without CS compensation, thermal dose values are overestimated in spiral data, and are spatially offset in 2DFT and EPI data. Compensating for heat-induced CS distortions improves the accuracy of temperature change and thermal dose measurements, and can have a significant positive impact on clinical and research applications of PRF-shift thermometry. [ABSTRACT FROM AUTHOR]

A major obstacle to the widespread adoption of HIFU therapy is the development of a suitable method of monitoring the ablation therapy in real-time. While MR-thermometry has emerged as a promising method for HIFU therapy monitoring, acoustic guidance has continuously been sought for reasons of cost and practicality. We have previously demonstrated the potential of acoustic thermometry, by using a recurrent neural network (RNN) to estimate changes in tissue temperature during HTFU ablation therapies. A limitation of this method is that an excessive therapeutic dose can cause multiple, non-linear changes within the ultrasound data, resulting in unreliable temperature estimates from the RNN. Accordingly, we pro pose a revised method of dosing wherein closed loop feedback is used to provide a controlled and specific dose; not only to ensure an efficacious lesion, but also to preserve the integrity of the ultrasound image, thereby producing accurate temperature estimates from the RNN. This investigation of controlling the thermal dose using feedback was performed on ex vivo bovine liver. The acoustic parameters used as inputs to the RNN were: changes in integrated backscatter intensity, thermal strain, and decollation. The therapeutic dose was delivered using a 1.1 MHz, 2D-array HIFU transducer transmitting at regular intervals during a 40-second dose. Interleaved between these regular HIFU dose intervals, volumetric ultrasound images were acquired on a Siemens ACUSON SC2000, with a 4Zlc probe. Feedback was introduced to the system by varying the HI FU duty cycle, in order to minimize the difference between a desired temperature curve (assigned a priori) and the estimated focal temperature values. Two methods were used for obtaining the focal temperature: the first was direct measurement using a 75-micron copper-constantan thermocouple embedded within the liver sample, and the second was temperature estimation as calculated from the RNN-based output temperatures estimated from the ultrasound data. The ability of each method to de liver a controlled. therapeutic dose was compared. The feedback controlled dosing both created effective lesions (an indicator of assured cell death), and also sustained the integrity of the ultrasound image signal features, preducing acceptably accurate temperature estimates. While thermocouple measured focal temperatures were more precise than the temperature estimates derived from RN N-based acoustic thermometry, effective therapeutic doses resulted from RN N guided treatment which maintained ultrasound feature quality. This approach to incorporating feedback in real-time RNN-based acoustic thermometry appears promising as a potential method of HIFU therapy monitoring and control. [ABSTRACT FROM AUTHOR]

Deviations in Q for resonant superconducting radio frequency niobium accelerator cavities are generally correlated with resistivity loss mechanisms. Field dependent Qs are not well modeled by these classical loss mechanisms, but rather can represent a form of precision cavity surface thermometry. When the field dependent Q variation shows improvement with increasing B field level the classical treatment of this problem is inadequate. To justify this behavior hydrogen as a ubiquitous impurity in niobium, which creates measurable property changes, even at very low concentrations is typically considered the cause of such anomalous behavior. This maybe the case in some instances, but more importantly any system operating with a highly coherent field with a significant time dependent magnetic component at near 2°K will have the ability to organize the remaining free spins within the London penetration depth to form a coupled energy reservoir in the form of low mass spin waves. The niobium resonant cavities are composed of a single isotope with a large nuclear spin. When the other loss mechanisms are stripped away this may be the gain medium activated by the low level residual magnetic fields. It was found that one resonant cavity heat treatment produced optimum surface properties and then functioned as a MASER extracting energy from the 2°K thermal bath while cooling the cavity walls. The cavity operating in this mode is a simulator of what can take place in the wider but not colder universe using the cosmic microwave background (CMB) as a thermal source. The low mass, long lifetimes, and the scale of the magnetic spin waves on the weakly magnetized interstellar medium allows energy to be stored that is many orders of magnitude colder than the cosmic microwave background. A linear accelerator cavity becomes a tool to explore the properties of the long wave length magnetic spin waves that populate this cold low energy regime. [ABSTRACT FROM AUTHOR]

Advancing the Nuclear Fuel Cycle and Next Generation Nuclear Power Plants requires enhancing our basic understanding of fuel and materials behavior under irradiation. The two most significant issues limiting the effectiveness and lifespan of the fuel are the loss of thermal conductivity of the fuel and the mechanical strength of both fuel and cladding. The core of a nuclear reactor presents an extremely harsh and challenging environment for both sensors and telemetry due to elevated temperatures and large fluxes of energetic and ionizing particles from radioactive decay processes. The majority of measurements are made in reactors using "radiation hardened" sensors and materials. A different approach has been pursued in this research that exploits high temperatures and materials that are robust with respect to ionizing radiation. This synergistically designed thermoacoustic sensor will be self-powered, wireless, and provide telemetry. The novel sensor will be able to provide reactor process information even if external electrical power and communication are unavailable. In addition, the form-factor for the sensor is identical to the existing fuel rods within reactors and contains no moving parts. Results from initial proof of concept experiments designed to characterize porosity, surface properties and monitor gas composition will be discussed. [ABSTRACT FROM AUTHOR]

Liquid hydrogen (LH2) is a key issue in a carbon-free energy infrastructure at the energy storage and transportation stage. The typical features of LH2 are low viscosity, large latent heat and small density, compared with other general liquids. It is necessary to measure a mass flow of liquid hydrogen with a simple and compact method, especially in a two phase separate flow condition. We have proposed applying a hot-wire type flow meter, which is usually used a for gas flow meter, to LH2 flow due to the quite low viscosity and density. A test model of a compact LH2 hot-wire flow meter to measure local flow velocities near and around an inside perimeter of a horizontal tube by resistance thermometry was designed and made. The model flow meter consists of two thin heater wires made of manganin fixed in a 10 mm-diameter and 40 mm-length tube flow path made of GFRP. Each rigid heater wire was set twisted by 90 degrees from the inlet to the outlet along the inner wall. In other words, the wires were aslant with regard to the LH2 stream line. The heated wire was cooled by flowing LH2, and the flow velocity was obtained by means of the difference of the cooling characteristic in response to the flow velocity. In this report, we show results on the basic experiments with the model LH2 hot-wire flow meter. First, the heat transfer characteristics of the two heater wires for several LH2 flow velocities were measured. Second, the heating current was controlled to keep the wire temperature constant for various flow velocities. The relations between the flow velocity and the heating current were measured. The feasibility of the proposed model was confirmed. [ABSTRACT FROM AUTHOR]

In this paper a comparison between the results of an uncertainties assessment, using different approaches, of the calibration of Standard Platinum Resistance Thermometers (SPRT) in fixed points are examined. Three different approaches are selected: classical GUM, propagation of probability distribution functions using Monte Carlo method, and the Bayesian approach. They are applied to the mathematical model proposed in the document "Uncertainties in the Realisation of the SPRT subranges of the ITS-90", prepared by the Working Group 3 of the Consultative Committee for Thermometry, and their results are discussed. [ABSTRACT FROM AUTHOR]

This work compares the extent of linear response regimes from standard time-resolving optical detectors for phosphor thermometry. Different types of Photomultipliers (ordinary and time-gated) as well as an Avalanche Photodiode are tested and compared using the phosphorescent time decay of CdWO4 that ranges from 10 μs down to a few ns within a temperature span of 290 to 580 K. Effects originating from incipient detector saturation, far from obvious to the operator's eye, are revealed as a change in evaluated phosphorescence decay time. Since the decay time of thermographic phosphors itself is used for temperature determination - systematic temperature errors up to several tens of Kelvins may be introduced by such detector saturation. A detector mapping procedure is suggested in order to identify linear response regions where the decay-to-temperature evaluation can be performed unbiased. Generation of such a library is highly recommended prior to any quantitative measurement attempt. Using this detector library, even signals collected in the partly saturated regime can be corrected to their unbiased value extending the usable detector operating range significantly. Further, the use of an external current-to-voltage amplifier proved useful for most applications in time-based phosphor thermometry helping to limit saturation effects whilst maintaining a reasonable bandwidth and signal outputs. [ABSTRACT FROM AUTHOR]

Laser induced phosphor thermometry as a reliable technique requires an analysis of factors controlling or contributing to the precision and accuracy of a measurement. In this paper, we discuss several critical design parameters in the development of luminescence lifetime-based phosphor thermometry instrumentation for use at elevated temperatures such as encountered in hot sections of gas turbine engines. As precision is predominantly governed by signal and background photon shot noise and detector noise, a brief summary is presented of how these noise contributions may affect the measurement. Accuracy, on the other hand, is governed by a range of effects including, but not limited to, detector response characteristics, laser-induced effects, the photo-physics of the sensor materials, and also the method of data reduction. The various possible outcomes of measurement precision and accuracy are discussed with luminescence lifetime measurements on Eu(III):YSZ sensor coatings. [ABSTRACT FROM AUTHOR]

We report new results for Johnson noise thermometry in the range 693 K to 800 K. The results are based on operation of a quantized voltage noise source (QVNS) which serves as a reference for the relative noise power spectral density. This paper describes the modifications to the system in order to overcome the limitations in our previous work and furthermore enable measurements of T-T90 at higher temperatures. [ABSTRACT FROM AUTHOR]

The eutectic Co-C melting point is a promising system to serve as a thermometric fixed-point in the temperature range above 1084.62 °C (copper freezing point). During the last decade, LNE-Cnam has developed and characterized some fixed-point devices, based on eutectic Co-C alloy, for applications to contact and radiation thermometry. Above 962 °C, the ITS-90 is realized by radiation thermometry by the extrapolation from a Ag, Au or Cu fixed point using the Planck law for radiation. So the only way for assigning a temperature in the scale to a Co-C cell (∼1324 °C) is by radiation thermometry. An indirect method is commonly used to assign a temperature to a high-temperature fixed point (HTFP) cell designed for contact thermometry is to fill a pyrometric cell with the same mixture as the contact thermometry cell. In this case, the temperature assigned to the pyrometric cell is attributed to the contact cell. This paper describes a direct method allowing the determination of the melting temperature realized by a "contact thermometry" Co-C cell by comparison to a "radiation thermometry" Co-C cell whose melting temperature was assigned in accordance to the scale by extrapolation from the Cu point. In addition, the same Co-C cell is studied with a standard Pt/Pd thermocouple. [ABSTRACT FROM AUTHOR]

Resistance thermometers using wires of rhodium with 0.5 mol % of iron (Rh-Fe thermometers or RIRTs) were first made by H Tinsley & Co in 1969 for applications at low temperatures, below the range where standard platinum resistance thermometers can be used, and down to 0.5 K or lower. They were investigated at NPL and found to have good sensitivity and excellent stability. Subsequently RIRTs have been used as the standard thermometers which record and compare the results of experiments in thermometry particularly below 24.5561 K, the triple-point of neon. From 1969 until the early 2000s, when Tinsley ceased to manufacture them, several hundred RIRTs were made and many were calibrated at NPL, NIST and elsewhere. In order to document the resistance-temperature characteristics of the production, and indicate the variability from batch to batch, the present paper analyses representative data for the resistance at the triple-point of water and the low-temperature calibrations of a number of thermometers produced at various times. The opportunity has been taken to include data for three RIRTs which were made independently, two in Russia and one in China. [ABSTRACT FROM AUTHOR]

The radiance temperature scale of KRISS has been realized from 273 K to 2900 K using two commercially available radiation thermometers. Above 873 K, we calibrate a silicon photodiode-based thermometer (LP4) with 4 spectral bands (650 nm, 750 nm, 850 nm and 900 nm) according to the definition of ITS-90 relying on the copper and silver point blackbodies and relative spectral responsivity measurements of LP4. The linearity of LP4 is measured by the flux-addition method using two LED arrays over the whole temperature range. The uncertainties of LP4 are confirmed by comparing the temperature difference between the silver and the copper point and by comparing the temperature scales for the 4 spectral bands. For the range from 273 K to 1234K, we calibrate a pyroelectric detector-based thermometer (TRT2) using Ice, Ga, In and Sn point blackbodies for the low range and using Sn, Zn, Al and Ag point blackbodies for the medium range. The uncertainties of the realized scale is 0.1 K to 1.3 K (k=2) from 273 K to 2900 K. The scales are confirmed by comparisons between them at the overlapped ranges and comparisons with an SPRT in a water bath blackbody. [ABSTRACT FROM AUTHOR]

Acoustic thermometry is the most accurate technique of primary thermometry ever devised. However, resonator based techniques are not practical and are rarely used in practice. Previously we have demonstrated the basic functionality of an acoustic thermometer operating at up to 1000 °C based on the time-of-flight measurements of short pulses in an acoustic waveguide. Here we report progress in assessing the practical and theoretical performance limitations of such a device. In this paper we report improvements in timing techniques which significantly improve the signal-to-noise ratio, a feature likely to be important in many industrial settings. We discuss the inference of the free field speed of sound from timing measurements and report results from a simple twin tube thermometer operating up to 500 °C. Finally we consider the shortcomings of current designs and prospects for future improvements including frequency domain analysis of the system. [ABSTRACT FROM AUTHOR]

An overview of the progress in High Temperature Fixed Point (HTFP) research conducted under the auspices of the CCT-WG5 research plan is reported. In brief highlights are: Provisional long term stability of HTFPs has been demonstrated. Optimum construction methods for HTFPs have been established and high quality HTFPs of Co-C, Pt-C and Re-C have been constructed for thermodynamic temperature assignment. The major sources of uncertainty in the assignment of thermodynamic temperature have been identified and quantified. The status of absolute radiometric temperature measurement has been quantified through the circulation of a set of HTFPs. The measurement campaign to assign low uncertainty thermodynamic temperatures to a selected set of HTFPs will begin in mid-2012. It is envisaged that this will be complete by 2015 leading to HTFPs becoming routine reference standards for radiometry and high temperature metrology. [ABSTRACT FROM AUTHOR]

In April 2011, a bilateral comparison of tin fixed point cells (231.928 °C) took place at the facilities of the Temperature group at the National Physical Laboratory (NPL). The comparison was with a standard from the Thermal Metrology Division of the National Institute of Metrology, Quality and Technology (INMETRO). It involved two cells: the test cell was an open one constructed in late 2010 at the INMETRO Thermometry Laboratory as part of an MSc research project; the reference cell was a sealed one, constructed in 2000 at NPL, traceable to the UK national standard tin point. The materials employed in the construction of the cells were from different suppliers. The cell design, dimensions and construction procedures were also different. Three standard platinum resistance thermometers (SPRTs), each different models from different manufacturers, were used to undertake the comparison, one from INMETRO and two from NPL. The comparison was performed in quadruplicate, each combination using a different freezing plateau. The differing self-heating behaviour of the different SPRTs was taken into account. The methodology employed in this comparison is detailed in the present paper. [ABSTRACT FROM AUTHOR]

A quantum-voltage-calibrated Johnson-noise thermometer was developed at NIM, which measures the Boltzmann constant k by comparing the thermal noise across a 100 Ω sense resistor at the temperature of the triple point of water with the pseudo-random frequency-comb voltage waveform synthesized with a bipolar-pulse-driven quantum-voltage-noise source. A measurement with integration period of 10 hours and bandwidth of 640 kHz resulted in a relative offset of 0.5×10-6 from the current CODATA value of k, and a type A relative standard uncertainty of 23×10-6. Benefiting from closely matched noise powers and transmission-line impedances and small nonlinearities in the cross-correlation electronics, the derived k shows self-consistent values and standard uncertainties for different measurement bandwidths. [ABSTRACT FROM AUTHOR]

The use of a combined microwave and acoustic resonator to determine the Boltzmann constant, kB, permits several checks on the internal consistency of the data. Using measurements in argon gas in the NPL-Cranfield quasispherical copper resonator (NPLC-2), we describe four distinct types of internal consistency check. Firstly, we estimate kB using six distinct acoustic resonances varying in frequency from 3.55 kHz to 21.77 kHz. We thus span a wide range of systematic corrections, most notably in the effect of the thermal boundary layer (TBL), which varies strongly with mode. Secondly, the same theory which predicts the TBL corrections to the acoustic resonance frequencies also predicts the widths of the resonances. By comparing the measured and theoretically-expected widths we can place limits on the effect of any un-modeled physics. Thirdly, the equivalent radius of the resonator (∼62.03 mm) is inferred from analysis of 8 TM microwave resonances and the spread of the radius values inferred from each mode is a measure of how well the resonator has been modeled. Finally, the microwave data can be used to check the inferred density of gas within the resonator. Based on measurements of the dielectric permittivity of the argon gas, pressure discrepancies greater than ±6 Pa can be detected at all pressures up to 700 kPa. Taken together, these four checks improve confidence in the final estimate for kB and restrict the types of systematic error which may affect the result. [ABSTRACT FROM AUTHOR]

Eccentric aiming is a common and general form in radiation thermometry. In such case, the correction of the size-of-source effect (SSE) is different from that under central aiming, under which the SSE has been characterized and can be easily corrected. The present article studies the eccentric SSE model on a polar coordinate, and the calculation of eccentric SSE requires integration. A polynomial is employed, as an approximation instead of an unintegrable item in the model under eccentric aiming to a circle radiation source, to obtain quasi-analytical solutions of the general and specific eccentric SSE functions. The characteristics of eccentric SSE are discussed, and examples of SSE calculation and correction are given. The SSE caused by eccentric aiming in measurements, such as distribution measurements, should be corrected or accounted in uncertainty for high accuracy of measurements, and can be corrected using the quasi-analytical solutions for circle source. [ABSTRACT FROM AUTHOR]

Cryogenic technology based on automated cryogen-free refrigerators has made substantial progress during the last decade making low temperatures easily accessible for a much broader community in science and industry. Along with this development there is a reinforced need in traceable thermometry for the cryogenic range. In this paper we give information about the realization, maintenance and dissemination of the PLTS-2000 at PTB. An updated uncertainty budget is presented for the PLTS-2000 applied for practical dissemination. We report on the investigation of dc-SQUID based noise thermometers which can be used as practical thermometers with a broad working range of more than 3 decades in temperature. On a future stage of development, such noise thermometers are intended to be used for solving the discrepancies in the background data of the PLTS-2000 at its lower end below 0.01 K. [ABSTRACT FROM AUTHOR]

Radiation thermometers measure the effective spectral radiation from a non-blackbody. Thus, the present study re-explains radiance thermometry using effective radiance temperature (ERT) suitable for an arbitrary temperature measurement in which ambient radiation exists. The theory of effective wavelength is adopted to elucidate the relationship between the "subjective" integral effective radiance temperature (the reading of an actual band-pass radiation thermometer) and the "objective" ERT by means of the integral intermediate value theorem, i.e., the value of integral effective radiance temperature measured by a thermometer is equal to ERT at the effective wavelength of the measurement. A unidirectional scanning approach for calculating the effective wavelength, with no iterative algorithm and suitable for existing multi-values, is introduced. The existence, non-monodromy, and geometric and physical meanings of the effective wavelength for an ERT measurement are discussed. ERT feature, which has a marked difference from that of classical radiance temperature, is expounded. ERT is more consistent with the nature of the apparent temperature and is more relevant in the discussion of the thermometric feature of a thermometer. Radiance temperature can be considered as a special case of ERT. [ABSTRACT FROM AUTHOR]

Phosphor thermometry is a semi-invasive surface temperature measurement technique utilizing the luminescence properties of thermographic phosphors. Typically these ceramic materials are coated onto the object of interest and are excited by a short UV laser pulse. Photomultipliers and high-speed camera systems are used to transiently detect the subsequently emitted luminescence decay point wise or two-dimensionally resolved. Based on appropriate calibration measurements, the luminescence lifetime is converted to temperature. Up to now, primarily Q-switched laser systems with repetition rates of 10 Hz were employed for excitation. Accordingly, this diagnostic tool was not applicable to resolve correlated temperature transients at time scales shorter than 100 ms. For the first time, the authors realized a high-speed phosphor thermometry system combining a highly repetitive laser in the kHz regime and a fast decaying phosphor. A suitable material was characterized regarding its temperature lifetime characteristic and precision. Additionally, the influence of laser power on the phosphor coating in terms of heating effects has been investigated. A demonstration of this high-speed technique has been conducted inside the thermally highly transient system of an optically accessible internal combustion engine. Temperatures have been measured with a repetition rate of one sample per crank angle degree at an engine speed of 1000 rpm. This experiment has proven that high-speed phosphor thermometry is a promising diagnostic tool for the resolution of surface temperature transients. [ABSTRACT FROM AUTHOR]

Despite the importance of resistance bridges in thermometry as fundamental instruments measuring resistance ratios of SPRTs, an accurate assessment of their nonlinearity and investigation of their behavior under various operating conditions have not been investigated much. Among various methods for nonlinearity assessment, a Hamon-type resistance network known to be RBC (resistance bridge calibrator) is widely used. However, due to finite temperature coefficients of base resistors used in the RBC, the evaluated nonlinearity of the resistance bridges under normal operating environment have been in doubt. In this work, to accurately evaluate the nonlinearity of the resistance thermometry bridge, an air medium thermostatted chamber having peak-to-peak temperature stability of around 0.1 °C was devised, and using this chamber, the nonlinearity of the resistance bridges at KRISS (two ASL F900s) was assessed. In addition to this, the behavior of the resistance bridge in terms of the nonlinearity was thoroughly investigated under different operating conditions of various gain and bandwidth combinations. The results showed that the resistance thermometry bridge marked the minimum nonlinearity of 11 ppb at 105 gain and 0.1 Hz bandwidth, and showed noticeable dependence on the gain. [ABSTRACT FROM AUTHOR]

For the last decade, the Thermometry Laboratory of the National Institute of Metrology, Quality and Technology (INMETRO) has been developing its own primary standards. In late 2010, a brand new fixed point cell containing high purity tin (99.9999 %) was constructed as the continuation of a project for constructing metal fixed-point cells in the positive range, in accordance with the temperature fixed-points described by the International Temperature Scale of 1990 (ITS-90) [1]. This is the fourth temperature fixed-point constructed by the laboratory team, which enables the performance of some calibrations without having to rely solely on commercially available cells. The materials and their preparation, the design, the procedures for the construction of the cell, the equipment, the investigation on its performance and its results will be detailed in the present paper. In addition, it is worth mentioning that this cell has recently taken part in a bilateral comparison with the National Physical Laboratory - NPL. [ABSTRACT FROM AUTHOR]

Controlled amounts of Si and Na impurities (0.1 to 0.5 μmol·mol-1 of Si and 0.2 to 1 μmol·mol-1 of Na) were diluted in the high-purity water of triple point of water (TPW) cells before sealing the cells. Water samples drawn from the manufactured doped cells were analyzed with high-resolution Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). The TPW temperature of one of the doped cells (the cell that showed a good agreement between the nominal Si and Na amounts and the Si and Na amounts measured by ICP-MS) was measured for different water/ice relative contents. The observed TPW depression was compared to 1) the TPW depression expected from the nominal doping and 2) the TPW depression expected from the total impurity content measured by ICP-MS. [ABSTRACT FROM AUTHOR]

To provide new determinations of the Boltzmann constant, k, which has been asked for by the International Committee for Weights and Measures concerning preparative steps towards new definitions of the kilogram, the ampere, the kelvin and the mole, an iMERAPlus joint research project has coordinated the European activities in this field. In this major European research project the Boltzmann constant has been determined by various methods to support the new definition of the kelvin. The final results of the project are reviewed in this paper. Determinations of the Boltzmann constant k were achieved within the project by all three envisaged methods: acoustic gas thermometry, Doppler broadening technique, and dielectric constant gas thermometry. The results were exploited by the interdisciplinary Committee on Data for Science and Technology (CODATA) in their 2010 adjustment of recommended values for fundamental constants. As a result, the CODATA group recommended a value for k with a relative standard uncertainty about a factor of two smaller than the previous u(k)/k of 1.7×10-6. [ABSTRACT FROM AUTHOR]

This paper illustrates a study conducted at INRIM, to further check how some quantities influence the value of the triple point temperature of the neon high-purity isotopes 20Ne and 22Ne. The influence of nitrogen as a chemical impurity in neon is critical with regard to the present best total uncertainty achieved in the measurement of these triple points, but only one determination is available in the literature. Checks are reported, performed on two different samples of 22Ne known to contain a N2 amount of 157·10-6, using two different models of sealed cells. The model of the cell can, in principle, have some effects on the shape of the melting plateau or on the triple point temperature observed for the sample sealed in it. This can be due to cell thermal parameters, or because the INRIM cell element mod. c contains many copper wires closely packed, which can, in principle, constrain the interface and induce a premelting-like effect. The reported results on a cell mod. Bter show no evident effect from the cell model and provide a value for the effect of N2 in Ne liquidus point of 8.6(1.9) μK ppm N2-1, only slightly different from the literature datum. [ABSTRACT FROM AUTHOR]

Phase transitions of pure substances provide the key reference temperatures, otherwise known as "defining fixed points", of the International Temperature Scale. At temperatures below the triple point of mercury (234.3156 K), the substances involved are gases at room temperature and include the triple points of hydrogen (13.8033 K), neon (24.5561 K), oxygen (54.3584 K) and argon (83.8058 K). The Consultative Committee for Thermometry also provides a list of "secondary reference points" whose quality approaches (or is equivalent to) that of the defining fixed points of the ITS Here, we report direct measurements of the triple point of krypton on the ITS-90, review the historical measurements that CCT WG2 relied upon for its 1996 assessment, and demonstrate that the triple point of krypton is a "first quality" secondary reference point. Based on our measurements, the temperature of the triple point of krypton is 115.7755 K ± 0.3 mK (k=1). [ABSTRACT FROM AUTHOR]

This paper identifies the influence variables affecting the resolution of thermometry resistance bridges. The theoretical limit to the resolution is determined by the spectral density of all noise sources, including the thermal noise from the resistors and amplifiers, quantization noise, and the equivalent noise bandwidth. Optimization of resolution is equivalent to minimization of measurement time, which has a Heisenberg-uncertainty-like relationship with equivalent noise bandwidth. Bridge design has a major influence on the compromises between the different noise sources, as well as influencing compromises with respect to measurement time. The paper explains the concept of an ideal averaging filter and illustrates the use of the Allan variance to evaluate the dependence of the resolution on measurement time. [ABSTRACT FROM AUTHOR]

Ultrafast compression provides unique insights into material behavior at extreme conditions. Starting from ambient conditions, compressed samples can reach pressures of 1-100+ GPa, accompanied by temperature changes of 102-105 K, within 10-100 ns. Dynamic temperature measurements of these states provide a wealth of thermodynamic information but are challenging in single-event experiments. Optical pyrometry can be used in some situations but becomes infeasible below 1000 K. Instead of inferring temperature based on light emitted by a sample, we propose to measure dynamic temperature states based on light reflected from a sample. As an active measurement, reflectance thermometry yields measurable optical signals at any temperature, potentially with nanosecond time resolution. [ABSTRACT FROM AUTHOR]

The emissivity uniformity of a blackbody cavity can be determined by emissivity at different locations and areas. We used the Monte Carlo method to calculate the local normal effective emissivity and average normal effective emissivity of isothermal concave cone, cylinder cone, cylinder, and cylinder-inner cone cavities with an identical length-radius ratio of six. The cylinder cavity has the highest uniformity, followed by the cylinder cone, cylinder-inner cone, and concave cone cavities. A cavity with both high uniformity as the cylinder cavity and insensitivity to specular reflection as the cylinder cone cavity has been demonstrated. [ABSTRACT FROM AUTHOR]

HiTeMS is a three-year research project involving fifteen partners, part funded by the European Metrology Research Programme. The objective of the research is to develop a suite of methods and techniques that will significantly improve the practice of industrial high temperature non-contact and contact thermometry, up to at least 2500 °C. Special emphasis is given to facilitating in-situ traceability, i.e. ensuring traceability to the International Temperature Scale of 1990 (ITS-90) directly within the industrial process. HiTeMS will do this by seeking to address common problems encountered in high temperature thermometry such as unknown emissivity and varying path transmission for non-contact thermometry and sensor characterization (including thermocouple reference function determination) and, characterizing and mitigating sensor drift (to at least 2000 °C). The project started in September 2011 and this paper focuses on the anticipated research outcomes by the time of the project conclusion in Aug 2014. [ABSTRACT FROM AUTHOR]

In preparation for re-determining the Boltzmann constant kB at NIM, we report studies of the longitudinal acoustic resonances in five, argon-filled, fixed-path-length cylindrical cavities. These cavity resonators differ in lengths, method of support, and gas fill ducts. The square of the apparent speed of sound c2 in each cavity deviates from reference values by linear functions of the pressure with mode-dependent, negative coefficients. Thus, all the resonators are more compliant than our models predict. The best-performing resonator was 80 mm long and 80 mm in diameter. For this resonator, the zero pressure limits of c2 for the four modes had a fractional standard deviation from their mean of 3.6×10-6. This suggests that we can reduce the uncertainty of our previous measurement of kB by a factor of two. [ABSTRACT FROM AUTHOR]

The ability to measure temperatures on high thermal loaded components in gas turbines and similar prime movers is critical during the design phase if the performance of cooling strategies is to be confirmed. Restricted access and the extreme environment mean that on-line temperature measurement is not always possible and that off-line temperature techniques employing thermal history sensors are sometimes necessary. The authors have developed a new type of sensor based on ceramic phosphors. These show bright narrow band emission that is easily detected and distinguished from the background. Crystallization, phase change and diffusion are all temperature dependent processes that affect the emission characteristics and that, with proper calibration, can be used to form a phosphor based thermal history sensor. Results from the calibration of crystallization in Y2SiO5:Tb and its application in the form of a temperature indicating paint are reviewed. A new embodiment of the phosphor thermal history sensor concept is then presented comprising a YSZ/YAG:Dy composite applied using air plasma spraying in the form of a thermal barrier coating. The coating is shown to function as a thermal history sensor albeit with a limited dynamic range. [ABSTRACT FROM AUTHOR]