Dynamic Measurements of the Temperature Coefficient of Resistance in the Transient Plane Source Sensor

The extended dynamic plane source (EDPS) method is one of the transient methods for measurements of the thermal conductivity and thermal diffusivity in solids. This technique uses a transient plane source (TPS) sensor, which serves as the heat source and thermometer. Its calibration consists of measuring the temperature dependence of the TPS sensor resistance and computing the temperature coefficient of resistance (TCR) using least-squares (LS) estimation. The goal of this study is to calibrate the TPS sensor directly in the apparatus for the EDPS method. The article presents an uncertainty assessment of the TCR measurement. The main sources of uncertainty stem from resistance measurements of the constant resistor and platinum thermometer calibration. The LS estimate of the TCR in a nickel TPS sensor is 4.83 × 10⁻³ K⁻¹ at 20 °C and 4.57 × 10⁻³ K⁻¹ at 45 °C with a combined standard uncertainty better than 0.04 × 10⁻³ K⁻¹, which is 0.7 %.     

Magnetic Field Dependence of a Capacitance Temperature Sensor

The influence of a magnetic field on the capacitance of a glass-ceramic temperature sensor (Lake Shore CS-501GR) has been measured extensively at temperatures down to 0.09 K and magnetic fields up to 12 T. While the influence of a magnetic field is still negligible at 4 K, the sensor shows an increasing non-monotonic dependence on the magnetic field with falling temperature. The maximum relative change of capacitance with respect to the zero field value remains smaller than 5 · 10⁻⁴. However, with the given sensitivity of the sensor, this small magnetoeffect may not be ignored in the low temperature region.     

A Noise Thermometer for Practical Thermometry at Low Temperatures

The application of a magnetic-field-fluctuation thermometer (MFFT) is described for practical thermometry in the low-temperature range. The MFFT inductively measures the magnetic noise generated by Johnson noise currents in a metallic temperature sensor. The temperature of the sensor is deduced from its thermal magnetic noise spectrum by applying the Nyquist theorem, making the thermometer in principle linear over a wide range of temperatures. In this setup, a niobium-based dc SQUID gradiometer detects the magnetic field fluctuations. The gradiometer design optimizes the inductive coupling to the metallic temperature sensor, yet equally ensures sufficient insensitivity to external magnetic interference. In order to obtain a highly sensitive and fast thermometer, the SQUID chip is placed directly onto the surface of the temperature sensor. The compact setup of the gradiometer/temperature sensor unit ensures good conditions for thermal equilibration of the sensor with the temperature to be measured, a factor that becomes increasingly important in the temperature range below 1 K. The first direct comparison measurements of the MFFT with a high-accuracy realization of the Provisional Low Temperature Scale of 2000 (PLTS-2000) are presented. Special emphasis is given to the investigation of the linearity, speed, and accuracy of the MFFT.     

Construction and use of a pulsed copper nuclear magnetic resonance thermometer

A pulsed nuclear magnetic resonance thermometer, constructed for temperature measurements below 0.5 K, is described. The nuclear free precession signal of copper nuclei is recorded with a gated low noise amplifier and with a phase sensitive detector gated to integrate the signal over an adjustable number of periods. The physical significance of the signal is discussed. A comparison of the resonance thermometer against a slurry type cerium magnesium nitrate (CMN) thermometer for the temperature region 10 mK to 100 mK is presented. The deviation Δ = T_NMR − T_CMN, representing the departure of the CMN thermometer from a Curie law behaviour, was measured as (0.5 ± 0.2) mK. In experiments with a nuclear refrigeration cryostat the resonance thermometer was calibrated against a nuclear orientation thermometer which provided an independent absolute temperature standard. At the low temperature end, from 1 mK to 10 mK, the linearity of the thermometer in T⁻¹ was confirmed by measurements of the nuclear spin-lattice relaxation time.     

A sensitive magnetic field sensor using BPSCCO thick film

A highly sensitive magnetic sensor operating at liquid nitrogen temperature and based on BPSCCO screen-printed thick film, is reported. The sensor resistance for an applied magnetic field of 100 ×10⁻⁴ T (100 gauss) exhibits an increase by 360% of its value in zero field at 77.4 K. The performance of the sensor in presence of magnetic field, the hysteretic features and the effect of thermal cycling, has been discussed.     

The specific heat capacity and thermal conductivity of normal liquid3He

By observing the diffusion of a heat pulse along a 10-cm column of normal liquid³He with the aid of two vibrating wire thermometers, it has been possible to measure the heat capacityC and thermal conductivityK of the liquid in the temperature range fromT _C to 10 mK and at pressures of 0.21, 4.39, 9.97, 20.01, and 29.32 bar. By using a Pt NMR thermometer, an LCMN thermometer, and a³He melting curve thermometer calibrated using the melting curve given by Greywall in 1983, a temperature scale has been established and (1) it has been shown that this melting curve is consistent in the temperature range 5–22 mK with the Korringa law for the Pt thermometer with a Korringa constant of 29.8±0.2 sec mK, (2) departures have been observed from the Curie-Weiss law for LCMN at low temperatures, and (3) values of the superfluid transition temperature have been obtained that are about 4% lower than the Helsinki values. The measured heat capacities agree well with those of Greywall, but values ofKT are higher than those of Greywall and show more temperature dependence below 10 mK. The implications for the present results of the very different melting curve given by Greywall in 1985 are discussed in an Appendix.     

Low-temperature thermometer using sputtered ZrNx thin film

A thin film thermometer using sputtered zirconium nitride has been investigated as a low-temperature thermometer. This film deposited on a sapphire substrate can be used to measure a wide temperature range from 1 to 300 K with reasonable sensitivity within a fast response time. The thermometer sensitivity can be altered by changing fabrication conditions. Moreover, the thermometer is almost insensitive to magnetic fields. The temperature error in a magnetic field of 6 T is less than 10 mK at 4.2 K.     

A High-Resolution Thermometer for the Range 1.6 to 5 K

This paper presents a detailed design, a theoretical analysis, and experimental tests of a high-resolution thermometer for use in the temperature range from 1.6 to 5 K. The device uses a dc-SQUID magnetometer to determine the change in magnetization with temperature of a paramagnetic salt in a magnetic field. The field is provided by a small permanent magnet attached to the thermometer. Measurements of the sensitivity of the device agree well with the theoretical analysis. Near 2.17 K (the superfluid transition of ⁴ He at saturated vapor pressure) the thermometer has a specific sensitivity of 4000 ₀ /K Gauss. There it achieves a temperature resolution better than 10 ^–9 K when it is charged with a field of about 300 Gauss. At 4.2 K, the specific sensitivity is smaller by a factor of 50, but should still allow temperature measurements with a resolution better than 10 ^–7 K. Near 2.17 K, drifts of the device are below the level of 10 ^–13 K/s. The thermometer has a small mass of about 7 g (excluding the magnet), and thus the advantage of relatively small cosmic radiation heating during microgravity experiments in Earth orbit.     

Realization of a 3He�C4He Vapor-Pressure Thermometer for Temperatures Between 0.65?K and 5?K at LNE-CNAM

In the temperature range between 0.65 K and 5 K, the International Temperature Scale of 1990 (ITS-90) is based on ³He and ⁴He vapor-pressure thermometers. Between 0.65 K and 1 K, the ITS-90 overlaps with the Provisional Low Temperature Scale of 2000 (PLTS-2000), defined in term of the melting pressure of ³He. Some differences, up to more than 1 mK, exist between the two scales in the overlapping interval. The LNE-CNAM has recently started the construction of a ³He?C⁴He vapor-pressure thermometer to realize the ITS-90 in its lowest subrange at the highest degree of accuracy. The device is provided with two separate vapor-pressure chambers, one for ³He and the other for ⁴He, built in a single copper block, and is installed in the experimental space of a dilution refrigerator. The vapor-pressure thermometer is designed to accommodate on the same copper block several transfer standards, an acoustic thermometer, and the ³He melting-pressure thermometer. This configuration is intended for realizing calibrations of transfer standards down to 0.65 K, for investigating the possibility to extend the acoustic thermometer below 4 K, and to perform a direct comparison between the ITS-90 and the PLTS-2000 in the overlapping temperature range, in order to study their differences. The realization of the system has been recently accomplished, and this report illustrates the characteristics of such an experimental device.     

Design and operation of a thermal sensor with micrometer-spatial resolution

We have developed a simple superconducting thin film device that can be used as either a thermometer or a thermal conductivity sensor. Over a narrow range the device has somewhat better temperature resolution than a conventional germanium thermometer, but its main advantage is that it has very high spatial resolution. The fabrication and operation of the device are described, together with preliminary results of experiments in which it is used to study liquid⁴He very nearT . Potential improvements are also discussed.     

The NPL InSb-based Radiation Thermometer for the Medium Temperature Range ( < 962°C)

Over the temperature range from 156 to 962°C, the NPL maintains a series of heatpipe blackbody sources for the calibration of customer sources, radiation thermometers, and thermal imagers. The temperature of each of the sources is determined using a calibrated platinum resistance thermometer or gold-platinum thermocouple placed close to the radiating surface at the back of the cavity. The integrity of such a blackbody source relies on it having good temperature uniformity, a high and well-known effective emissivity, and having the sensor in good thermal contact with the cavity. To verify the performance of the blackbody sources, it is necessary to use an infrared thermometer that has been independently calibrated to compare the radiance temperature of the source with the temperature measured by the contact sensor. Such verification of the NPL blackbodies has been carried out at short wavelengths: from 500 to 1,000°C using the NPL LP2 calibrated using the NPL gold point, and at 1.6 μm using an InGaAs-based radiation thermometer calibrated at a series of fixed-points from indium (156°C) to silver (962°C). Thermal imaging systems traditionally operate over the 3–5 μm waveband and are calibrated using NPL sources. Up until now, it has not been possible to verify the performance of the sources in this waveband except indirectly by cross-comparison of the sources where they overlap in temperature. A mid-infrared (nominally 3–5 μm) radiation thermometer has, therefore, been designed, constructed, and validated at NPL. The instrument was validated and calibrated using the fixed-point blackbody sources and then used to validate the heatpipe blackbodies over their temperature range of operation. The results of the instrument validation and blackbody measurements are given.     

Electrical resistivity of Mn-doped SnTe crystals at low temperature

The temperature dependence of the resistivity over the range 1.8–20 K has been measured on the narrow-gap semiconductor SnTe with various Mn contents (<2.2at.%) and carrier concentrations [p = (1.2–8) × 10²⁰ cm^–3]. The resistivity shows an anomaly at some magnetic ordering temperature T _m, which depends sublinearly on the Mn content c, but not linearly. However, together with a negative magnetoresistance, we have confirmed that the carrier scattering in this crystal is due to the s-d interaction as in dilute magnetic alloys.     

Magnetic thermometry to below one millikelvin with lanthanum-diluted cerium magnesium nitrate

Measurements are presented of the pressure and magnetic temperature coordinates of the phase diagram of liquid ³He using a powdered Ce_0.05La_0.95 magnesium nitrate thermometer in the shape of a right circular cylinder with diameter equal to height. The lowest magnetic temperature observed with the thermometer is 0.41 mK. The magnetic temperature of the intersection of the second-order line with the melting curve is 2.625 mK, and the critical temperature at zero pressure is 1.055 mK. The difference between T _c ^* and T _AB ^* extrapolated to melting pressure is 0.57 mK, in excellent agreement with the difference T _A-T_B found from measurements along the melting curve. The present data are compared with the La Jolla provisional absolute scale based on noise thermometry and zero sound. We make the assumption that the absolute temperature T and the present magnetic temperature T ^* are related by T = T ^* + and use the resultant scale to reanalyze a variety of experimental results that had been given in terms of the La Jolla provisional scale.Work supported by the U.S. Department of Energy under contract EY-76-S-03-0034, P.A. 143.     

Dual function sensors for concurrent measurement of temperature and magnetic field in cryogenic applications

Dual function sensors (DFSs) for concurrent measurement of temperature and magnetic field in cryogenic applications have been developed and characterized. The DFS consists of a Ge-on-GaAs film resistance thermometer and an InSb-on-GaAs film Hall-effect magnetic field sensor combined in a single package with dimensions: 3.5 mm wide, 2.2 mm thick and 10.1 mm long. The construction and characteristics of two models of the DFSs; which are intended to provide measurements of temperature in the 1.5–400 K and 0.1–400 K ranges, and magnetic fields up to 30 T, are presented.     

Search for superconductivity in lithium and magnesium

Recent theoretical work suggests that magnesium and lithium should be superconducting in the m°K temperature range. We have cooled samples of each of these metals to a temperature of 4 m°K, measured by a gamma-ray anisotropy thermometer. Although the magnetic field was less than 10^–2 Oe, no superconducting transitions were observed. The use of a nuclear orientation thermometer employing⁶⁰Co in single crystal (hcp) cobalt is described.Work supported in part by the U.S. Atomic Energy Commission, and in part by ARPA, U.S. Department of Defense.     

An intercomparison of a Cu nuclear susceptibility thermometer and an Sn99 mösbauer effect thermometer between 6 mK and 1 K

The cold-absorber Sn¹¹⁹ Mössbauer effect thermometer discussed by Parshin et al, has been compared with the steady-field Cu nuclear magnetic susceptibility thermometer. The Curie constant of the Cu thermometer was also determined from simultaneous measurements using a ballistic CMN thermometer. The sensors were installed in the mixing chamber of a dilution refrigerator capable of producing temperatures below 6 mK in the single cycle mode. The absorber never cooled below 7.8 mK due to heat leaks. Good consistency and reproducibility were established between 10 and 100 mK.     

Measurement of absolute intensity of weak magnetic fields using rf biased SQUID

A method to measure the absolute intensity of a weak magnetic field is described. We used a superconducting material as a sensor and detected its magnetization change between the superconducting state and the normal state at the transition temperature. The magnetization change measured by the SQUID system is proportional to the component of the absolute intensity of the magnetic field at the superconductor specimen which in parallel with the axis of the astatic pick up coils. A resolution as good as 10^?5 Oe has been obtained. The practical limit of the resolution of this method is also discussed.     

PdMn and PdFe: New Materials for Temperature Measurement Near 2 K

Interest in the critical dynamics of superfluid ⁴ He in microgravity conditions has motivated the development of new high resolution thermometry technology for use in space experiments near 2 K. We have developed a magnetic thermometer using dilute magnetic alloys of Mn or Fe dissolved in a pure Pd matrix, similar to previous thermometers used at ultra-low temperatures. These metallic thermometers are easy to fabricate, chemically inert, and can have a low thermal resistance to the stage to be measured. Also, the Curie temperature can be varied by changing the concentration of Fe or Mn, making them available for use in a wide temperature range. The derivative of the magnetic susceptibility was measured for PdMn and PdFe between 1.5 K and 4 K using a SQUID magnetometer. These measurements, as well as preliminary noise and drift measurements, show them to have sub-nK resolution with a drift of less than 10 ^–13 K/s.