Vortex Shedding from an Object Moving in Superfluid $$^4\hbox {He}$$ at mK Temperatures and in a Bose–Einstein Condensate

Vortex shedding from a microsphere oscillating in superfluid \(^4\hbox {He}\) at mK temperatures is compared with that from a laser beam moving in a Bose–Einstein condensate as observed by other authors. In particular, in either case a linear dependence of the shedding frequency \(f_v\) on \(\varDelta v = v - v_c\) is observed, where v is the velocity amplitude of the sphere or the constant velocity of the laser beam above a critical velocity \(v_c\) for the onset of turbulent flow: \(f_v = a \,\varDelta v\), where the coefficient a is proportional to the oscillation frequency \( \omega \) above some characteristic frequency \(\omega _k\) and assumes a finite value for steady motion \(\omega \rightarrow 0\).     

Thermodynamic Temperature Measurement to the Indium Point Based on Radiance Comparison

A multi-national project (the EMRP InK project) was completed recently, which successfully determined the thermodynamic temperatures of several of the high-temperature fixed points above the copper point. The National Metrology Institute of Japan contributed to this project with its newly established absolute spectral radiance calibration capability. In the current study, we have extended the range of thermodynamic temperature measurement to below the copper point and measured the thermodynamic temperatures of the indium point (\(T_{90} =\) 429.748 5 \(\hbox {K}\)), tin point (505.078 K), zinc point (692.677 K), aluminum point (933.473 K) and the silver point (1 234.93 K) by radiance comparison against the copper point, with a set of radiation thermometers having center wavelengths ranging from \(0.65\,\upmu \hbox {m}\) to \(1.6\,\upmu \hbox {m}\). The copper-point temperature was measured by the absolute radiation thermometer which was calibrated by radiance method traceable to the electrical substitution cryogenic radiometer. The radiance of the fixed-point blackbodies was measured by standard radiation thermometers whose spectral responsivity and nonlinearity are precisely evaluated, and then the thermodynamic temperatures were determined from radiance ratios to the copper point. The values of \(T-T_{90}\) for the silver-, aluminum-, zinc-, tin- and indium-point cells were determined as ?4 mK (\(U = 104\,\hbox {mK}, k=2\)), ?99 mK (88 mK), ?76 mK (76 mK), ?68 mK (163 mK) and ?42 mK (279 mK), respectively.     

NRC Microwave Refractive Index Gas Thermometry Implementation Between 24.5 K and 84 K

The implementation of microwave refractive index gas thermometry at the National Research Council between 24.5 K and 84 K is reported. A new gas-handling system for accurate control and measurement of experimental gas pressure has been constructed, and primary thermometry measurements have been taken using a quasi-spherical copper resonator and helium gas at temperatures corresponding to three defining fixed points of the International Temperature Scale of 1990 (ITS-90). These measurements indicate differences between the thermodynamic temperature T and ITS-90 temperature \(T_{90}\) of \(\left( T - T_{90} \right) = -0.60 \pm 0.56\) mK at \(T_{90} = 24.5561\) K, \(\left( T - T_{90} \right) = -2.0 \pm 1.3\) mK at \(T_{90} = 54.3584\) K, and \(\left( T - T_{90} \right) = -4.0 \pm 2.9\) mK at \(T_{90} = 83.8058\) K. The present results at \(T_{90} = 24.5561\) K and \(T_{90} = 83.8058\) K agree with previously reported measurements from other primary thermometry techniques of acoustic gas thermometry and dielectric constant gas thermometry, and the result at \(T_{90} = 54.3584\) K provides new information in a temperature region where there is a gap in other recent data sets.     

The Influence of Impurities on the Zinc Fixed Point

Impurities are considered to be the most significant source of uncertainty for the realization of the International Temperature Scale of 1990 by means of metal fixed points. The determination and further reduction in this uncertainty require a traceable chemical analysis of dissolved impurities in the fixed-point metal and accurate knowledge of the specific temperature change caused by impurities (slope of the liquidus line). We determined the slope of the liquidus line for three binary systems and present results and conclusions from the chemical analysis of zinc with a nominal purity of 7N. For the Fe–Zn system, we determined a liquidus slope of (\(-0.91\pm 0.14\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of freezing plateaus and (\(-0.76~\pm 0.20\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) from the evaluation of melting plateaus; for the Pb–Zn system, the corresponding results are (\(-0.27~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)) and (\(-0.26~\pm 0.05\)) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)). Although for the Sb–Zn system, we determined a liquidus slope of about \(-0.8\) mK / (\(\upmu \hbox {g}{\cdot }\hbox { g}^{-1}\)), our investigations showed that a correction of the influence of antimony is highly questionable because antimony can be found in zinc in a fully dissolved state or precipitated as an insoluble compound. Iron is the only impurity where a correction of the fixed-point temperature was possible. For the realization of the zinc fixed point at PTB, this correction is between 2 \(\upmu \)K and 16 \(\upmu \)K depending on the batch of zinc used. The influence of the sum of all impurities was estimated by means of the OME method. The resulting uncertainty contribution is between 12 \({\upmu }\hbox {K}\) and 48 \({\upmu }\hbox {K}\).     

Nonlinear Ultrasound Propagation in Solid $$^4\hbox {He}$$ Compared with Shear Modulus Experiments

Ultrasound attenuation (\(\alpha \)) and velocity (V) at 9.6 MHz are measured in polycrystalline hcp \(^4\hbox {He}\). The ultrasound signal above 200 mK is linear and understood in terms of resonant vibration of dislocation segments pinned between network nodes with an average pinning length of 3.7 \(\mu \hbox {m}\), much shorter than 59 \(\mu \hbox {m}\) estimated from a shear modulus measurement. Dramatic changes in \(\alpha \) and V are observed below 200 mK. The changes are strongly dependent on temperature and are nonlinear and hysteretic. These effects result from pinning of dislocations by \(^3\hbox {He}\) impurities (nominal concentration of 0.3 ppm). The dislocation damping constant due to thermal phonons, the binding energy between dislocation and \(^3\hbox {He}\), and the average network pinning length obtained from the ultrasound data are compared with those from the shear modulus experiments.     

Ultra-High Q Acoustic Resonance in Superfluid $$^$$He

We report the measurement of the acoustic quality factor of a gram-scale, kilohertz-frequency superfluid resonator, detected through the parametric coupling to a superconducting niobium microwave cavity. For temperatures between 400 mK and 50 mK, we observe a \(T^{-4}\) temperature dependence of the quality factor, consistent with a 3-phonon dissipation mechanism. We observe Q factors up to \(1.4\times 10^8\), consistent with the dissipation due to dilute \(^3\)He impurities, and expect that significant further improvements are possible. These experiments are relevant to exploring quantum behavior and decoherence of massive macroscopic objects, the laboratory detection of continuous gravitational waves from pulsars, and the probing of possible limits to physical length scales.     

Measurement of Out-of-Plane Thermal Conductivity of Epitaxial $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-{\delta }}$$ Thin Films in the Temperature Range from 10 K to 300 K by Photothermal Reflectance

We measured the out-of-plane (c-axis) thermal conductivity of epitaxially grown \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-{\delta }}\) (YBCO) thin films (250 nm, 500 nm and 1000 nm) in the temperature range from 10 K to 300 K using the photothermal reflectance technique. The technique enables us to determine the thermal conductivity perpendicular to a thin film on a substrate by curve fitting analysis of the phase lag between the thermoreflectance signal and modulated heating laser beam in the frequency range from \(10^{2}\,\hbox {Hz}\) to \(10^{6}\,\hbox {Hz}\). The uncertainties of measured thermal conductivity of all samples were estimated to be within \({\pm }9\,\%\) at 300 K, \({\pm }12\,\%\) at 180 K, \({\pm }16\,\%\) at 90 K and \({\pm }20\,\%\) below 50 K. The experimental results show that the thermal conductivity is dependent on the thickness of the thin films across the entire temperature range. We also observed that the thermal conductivity of the present YBCO thin films showed \(T^{1.4}\) to \(T^{1.6}\) glass-like dependence below 50 K, even though the films are crystalline solids. In order to explain the reason for this temperature dependence, we attempted to analyze our results using phonon relaxation times for possible phonon scattering models, including stacking faults, grain boundary and tunneling states scattering models.     

A Sub-millikelvin Calibration Facility in the Range 0 $$^{\circ }$$C to 30 $$^{\circ }$$C

A new sub-millikelvin calibration facility for the range 0 \(^{\circ }\)C to 30 \(^{\circ }\)C is described, that allows calibration of customer thermometers, other than standard platinum resistance thermometers, with an uncertainty lower than 1 millikelvin. The improvements with respect to the traditional calibration facility are reported with particular emphasis on the temperature control (better than 0.2 mK), resistance measurement and calibration procedure. The new facility was validated by using 6 standard platinum resistance thermometers and the calibration uncertainty in the range from 0 \(^{\circ }\)C to 30 \(^{\circ }\)C amounted to 0.31 mK–0.35 mK. To demonstrate the potentiality of this facility, two oceanographic thermometers, Sea-Bird Electronics SBE 3 and SBE 35, were calibrated with an expanded uncertainty of 0.8 mK (\(k=2\)).     

Realization of PLTS-2000 for Low-Temperature Resistance Thermometer Calibration Services Below 650 mK

In this study, the Provisional Low Temperature Scale of 2000 (PLTS-2000) was realized below 650 mK for the purpose of launching low-temperature resistance thermometer calibration services in Japan. A Straty–Adams-type \(^{3}\)He melting pressure thermometer (MPT) and a dilution refrigerator were used to realize the PLTS-2000. Offsets due to hydrostatic pressure head in a filling capillary line of the MPT were adjusted using the minimum pressure fixed point on the \(^{3}\)He melting curve. A rather large MPT hysteresis between the decreasing and increasing pressures was observed during pressure calibration of the MPT and was the main source of uncertainty. The combined standard uncertainty (\(k = 1\)) between 50 mK and 650 mK was estimated to be in the range of 0.40 mK to 2.62 mK. The MPT and a number of resistance thermometers with negative temperature coefficients were mounted on the experimental platform with a thermal connection to a mixing chamber and compared in a multiple-temperature-point calibration. The temperature range around the melting pressure minimum, 250 mK to 400 mK, was not used for the calibration. The expanded uncertainty (\(k = 2\)) in the calibration based on realization of the PLTS-2000 between 50 mK and 650 mK was estimated to be in the range of 0.86 mK to 5.25 mK.     

Critical Parameters and Critical-Region ($$p,\rho,T)$$ Data of trans-1,1,1,3-Tetrafluorobut-2-ene [HFO-1354mzy(E)]

This study presents the experimental measurement of the \(p\rho T\) properties and critical parameters of a low GWP type refrigerant, trans-1,1,1,3-Tetrafluorobut-2-ene (HFO-1354mzy(E)). The sample purity of the substance was 99 area %. \(p \rho T\) property measurements and visual observations of the meniscus of HFO-1354mzy(E) were carried out using a metal-bellows volumometer with an optical cell. The critical temperature was determined by observation of the critical opalescence. The critical pressure and critical density were determined as the inflection point of the isothermal \(p \rho T\) property data at the critical temperature. For more precise clarification of the thermodynamic surface in the vicinity of the critical point, additional \(p \rho T\) property measurements were carried out on three isotherms in the supercritical region. The expanded uncertainties (\(k = 2\)) in the temperature, pressure, and density measurements were estimated to be less than 3 mK, 1.2 kPa, and 0.32 \(\hbox {kg} \cdot \hbox {m}^{-3}\), respectively. The expanded uncertainties of the critical parameters were estimated to be less than 13 mK, 1.4 kPa, and 2.3 \(\hbox {kg} \cdot \hbox {m}^{-3}\), respectively. These values are the first reported for HFO-1354mzy(E) and are necessary for the development of its equation of state in the near future.     

The Damping and Drag Coefficient of Quartz Tuning Fork in Superfluid $$^{3}\hbox {He}$$–$$^{4}\hbox {He}$$4He Solutions in the Laminar Flow

The \(^{3}\)He impurity influence on the oscillations of a quartz resonator and thus its drag coefficient in a laminar flow of a superfluid \(^{3}\)He–\(^{4}\)He mixture has been investigated. The temperature dependences of the resonance curves were measured on quartz tuning forks with a resonance frequency 32 kHz in vacuum in superfluid mixtures with \(^{3}\)He concentrations of \(x_{3}=0.05\) and 0.15 in a wide range of driving forces at temperatures from 0.5–2.5 K. The results obtained were used to plot the temperature dependence of the drag coefficient. With the help of the normalization on the effective area of the oscillating body, the concentration dependence of the drag coefficient of the quartz tuning fork and the vibrating sphere in superfluid solutions has been constructed and analyzed.     

Influence of $$^$$He Coverage on Resonance Properties of a Quartz Tuning Fork Immersed in Liquid $$^3$$3He

Nowadays quartz tuning forks are commonly used for temperature measurements in experiments with liquid (both normal and superfluid) \(^3\)He. In most of the experiments pure \(^3\)He is used, but in some cases \(^4\)He is added in order to cover surfaces by a few monolayers of \(^4\)He. We report here measurements of influence of different \(^4\)He coverages on the fork resonance properties at different pressures. We have found that the presence of even small amounts of paramagnetic \(^3\)He on the fork surface may essentially change the temperature calibration.     

Magnetism in Solid Oxygen Studied by High-Pressure Neutron Diffraction

A systematic modification of the entropy trajectory (\(S_\mathrm{m}(T)\)) is observed at very low temperature in magnetically frustrated systems as a consequence of the constraint (\(S_\mathrm{m}\ge 0\)) imposed by the Nernst postulate. The lack of magnetic order allows to explore and compare new thermodynamic properties by tracing the specific heat (\(C_\mathrm{m}\)) behavior down to the sub-Kelvin range. Some of the most relevant findings are: (i) a common \(C_\mathrm{m}/T|_{T\rightarrow 0} \approx 7\) J/mol K\(^2\) ‘plateau’ in at least five Yb-based very-heavy-fermions (VHF) compounds; (ii) quantitative and qualitative differences between VHF and standard non-Fermi-liquids; (iii) entropy bottlenecks governing the change of \(S_\mathrm{m}(T)\) trajectories in a continuous transition into alternative ground states. A comparative analysis of \(S_\mathrm{m}(T\rightarrow 0)\) dependencies is performed in compounds suitable for adiabatic demagnetization processes according to their \(\partial ^2 S_\mathrm{m}/\partial T^2\) derivatives.     

Dry Block Calibrator with Improved Temperature Field and Integrated Fixed-Point Cells

To reduce uncertainty of calibrations of contact thermometers using dry block calibrators, a concept was developed at Institute for Process Measurement and Sensor Technology of Technische Universität Ilmenau. This concept uses a multi-zone heating, heat flux sensors and a multiple fixed-point cell. The paper shows the concept and its validation on the basis of a dry block calibrator with a working temperature range of \(70\,^{\circ }\hbox {C}\) to \(430\,^{\circ }\hbox {C}\). The experimental results show a stability of \({\pm } 4\,\hbox {mK}\) for the reference temperature and axial temperature differences in the normalization block less than \({\pm }55\,\hbox {mK}\).     

Thermal Conductivity and Thermal Boundary Resistances of ALD Al$$_{}$$O$$_{3}$$3 Films on Si and Sapphire

On Si and sapphire substrates, 6–45 nm thick films of atomic layer-deposited Al\(_{2}\)O\(_{3}\) were grown. The thermal conductivity of ALD films has been determined from a linear relation between film thickness and thermal resistance measured by the 3\(\omega \) method. ALD films on Si and sapphire showed almost same thermal conductivity in the temperature range of 50–350 K. Residual thermal resistance was also obtained by extrapolation of the linear fit and was modeled as a sum of the thermal boundary resistances at heater–film and film–substrate interfaces. The total thermal resistance addenda for films on sapphire was close to independently measured thermal boundary resistance of heater–sapphire interface. From the result, it was deduced that the thermal boundary resistance at ALD Al\(_{2}\)O\(_{3}\)–sapphire interface was much lower than that of heater–film. By contrast, the films on Si showed significantly larger thermal boundary resistance than films on sapphire. Data of \(< 30\) nm films on Si were excluded because an AC coupling of electrical heating voltage to semiconductive Si complicated the relation between 3\(\omega \) voltage and temperature.     

Study of the Choice of Excitation Frequency for Sub Surface Defect Detection in Electrically Thick Conducting Specimen Using Eddy Current Testing

Understanding the scope and limitations of non-destructive testing procedure is essential for selecting the appropriate test parameters for material inspection. This paper presents the scope of material (\( \delta_{s} \)) and probe dependent (\( \delta_{t} \)) penetration depths for determining the optimal test frequency (\( f_{opt} ) \) for detection of sub surface defects in electrically thick conducting specimens. Numerical modelling is carried out for a pancake coil above an electrically thick aluminium plate, \( t/\delta_{t} \)?>?1, to study the influence of the EC probe and defect location (\( t_{df} \)) on the test frequency for near and deep sub surface defects. The study concludes that the optimal test frequency, \( f_{opt} \) for detection of deep sub surface defects (\( t_{df} /t \approx 1 \)) is determined by the probe dependent skin depth, \( \delta_{t} \), and the plate thickness is related to \( f_{opt} \) by, \( t \propto 1/\sqrt {f_{opt} } \). The numerical observations were experimentally validated for machined sub surface notches on a 10 mm thick (\( t \)) aluminium plate.     

Measurement of the Nonlinearity of Heat-Flux Sensors Employing a $$\hbox {CO}_2$$ laser

Heat-flux sensors are widely used in industry to test building products and designs for resistance to bushfire, to test the flammability of textiles and in numerous applications such as concentrated solar collectors. In Australia, such detectors are currently calibrated by the National Measurement Institute Australia (NMIA) at low flux levels of 20 W \(\cdot \) m\(^{-2}\). Estimates of the uncertainty arising from nonlinearity at industrial levels (e.g. 50 kW \(\cdot \) m\(^{-2}\) for bushfire testing) rely on literature information. NMIA has developed a facility to characterize the linearity response of these heat-flux sensors up to 110 kW \(\cdot \) m\(^{-2}\) using a low-power \(\hbox {CO}_2\) laser and a chopped quartz tungsten–halogen lamp. The facility was validated by comparison with the conventional flux-addition method, and used to characterize several Schmidt–Boelter-type sensors. A significant nonlinear response was found, ranging from (\(3.2 \pm 0.9\))% at 40 kW \(\cdot \) m\(^{-2}\) to more than 8 % at 100 kW \(\cdot \) m\(^{-2}\). Additional measurements confirm that this is not attributable to convection effects, but due to the temperature dependence of the sensor’s responsivity.     

Effect of Al$$_$$O$$_3$$3 Nanoparticles Additives on the Density,Saturated Vapor Pressure,Surface Tension and Viscosity of Isopropyl Alcohol

This paper presents results of an experimental study of the density, saturated vapor pressure, surface tension and viscosity of Al\(_2\)O\(_3\) nanoparticle colloidal solutions in isopropyl alcohol. Studies of the thermophysical properties of nanofluids were performed at various temperatures and concentrations of Al\(_2\)O\(_3\) nanoparticles. The paper gives considerable attention to a turbidimetric analysis of the stability of nanofluid samples. Samples of nanofluids remained stable over the range of parameters of the experiments, ensuring the reliability of the thermophysical property data for the Al\(_2\)O\(_3\) nanoparticle colloidal solutions in isopropyl alcohol. The studies show that the addition of Al\(_2\)O\(_3\) nanoparticles leads to an increase of the density, saturated vapor pressure and viscosity, as well as a decrease for the surface tension of isopropyl alcohol. The information reported in this paper on the various thermophysical properties for the isopropyl alcohol/Al\(_2\)O\(_3\) nanoparticle model system is useful for the development of thermodynamically consistent models for predicting properties of nanofluids and correct modeling of the heat exchange processes.     

Establishment of the Co-C Eutectic Fixed-Point Cell for Thermocouple Calibrations at NIMT

In 2015, NIMT first established a Co-C eutectic temperature reference (fixed-point) cell measurement capability for thermocouple calibration to support the requirements of Thailand’s heavy industries and secondary laboratories. The Co-C eutectic fixed-point cell is a facility transferred from NPL, where the design was developed through European and UK national measurement system projects. In this paper, we describe the establishment of a Co-C eutectic fixed-point cell for thermocouple calibration at NIMT. This paper demonstrates achievement of the required furnace uniformity, the Co-C plateau realization and the comparison data between NIMT and NPL Co-C cells by using the same standard Pt/Pd thermocouple, demonstrating traceability. The NIMT measurement capability for noble metal type thermocouples at the new Co-C eutectic fixed point (\(1324.06\,{^{\circ }}\hbox {C}\)) is estimated to be within \(\pm 0.60\,\hbox {K}\) (\(k=2\)). This meets the needs of Thailand’s high-temperature thermocouple users—for which previously there has been no traceable calibration facility.