K. Yamazawa

Volume measurements of 28Si spheres using an interferometer with a flat etalon to determine the Avogadro constant

The volumes of two 1 kg silicon spheres, AVO28-S5 and AVO28-S8, fabricated from a 28Si-enriched crystal were measured to determine the Avogadro constant by the x-ray crystal density method in the International Avogadro Coordination Project. The volumes were determined from diameter measurements of the two spheres using a laser interferometer with a flat etalon. In the diameter measurement, the sphere was placed between the two flat etalon plates. The gaps between the sphere and the etalon plates and the distance between the etalon plates were measured by phase-shifting interferometry with optical frequency tuning. The apparent volumes of the 28Si spheres were determined from the diameter measurement in many directions with relative combined standard uncertainties of 5.0 × 10−8 and 4.4 × 10−8 for AVO28-S5 and AVO28-S8, respectively. The effect of the surface layer on the diameter measurement was evaluated on the basis of the results of characterizing the sphere surface. By taking into account the effect of the surface layer, the silicon core volume excluding the surface layer and the actual volume including the surface layer were also determined. Details of the interferometer, data analysis and the uncertainty in the measurement are described.

Estimation of impurity effect in aluminium fixed-point cells based on thermal analysis

The impurity effect on fixed-point temperature realization by thermal analysis has been assessed. For such an assessment, the following actions were conducted: (1) the fabrication of aluminium point cells using 6N or higher-grade aluminium samples from different sources (manufacturers), (2) temperature measurements during solidification and thermal analyses based on freezing curves obtained from the measurements, (3) direct cell comparison among cells of different nominal purities and (4) calculation of the departure of the freezing point from the ideally defined freezing point by applying the sum of individual estimates (SIE). Two aluminium point cells were prepared in action (1) using 6N-grade and one cell using 6N5-grade aluminium samples. To realize a fixed point using the cells, a fixed-point furnace was developed and evaluated. Temperature measurements in action (2) were conducted at different rates of solidification and in accordance with the one using the liquid–solid interface technique. Gradients of freezing curves were derived in the thermal analysis, and from their dependence on the rate of solidification, the impurity effect was evaluated. Indirect cell comparison was also derived using the difference in the gradients. It was found that the indirect cell comparison was in satisfactory agreement with the direct cell comparison, which was obtained from action (3). It was also found that the departure of the thermal analysis from the SIE obtained from action (4) was within the uncertainty. This fact may imply a possible application of thermal analysis for estimating the effect of impurities in the realization of the aluminium point, especially for 6N-grade aluminium fixed-point cell as used in the present study.

Deep Ocean Temperature Measurement with an Uncertainty of 0.7 mK

AbstractThe uncertainty of deep ocean temperature (~1°C) measurement was evaluated. The time drifts of six deep ocean standards thermometers were examined based on laboratory calibrations as performed by the manufacturer in triple point of water (TPW) cells and gallium-melting-point (GaMP) cells. The time drifts ranged from −0.11 to 0.14 mK yr−1. Three of the six thermometers were evaluated at the National Metrology Institute of Japan in five TPW cells and a GaMP cell, and the temperature readings agreed with the realized temperature of the national standard cells of Japan within ±0.14 and ±0.41 mK for TPW and GaMP, respectively. The pressure sensitivities of the deep ocean standards thermometers were estimated by comparison with conductivity–temperature–depth (CTD) thermometers in the deep ocean, and no notable difference was detected. Pressure sensitivities of the two CTD thermometers were examined by laboratory tests, and the results suggest that the deep ocean standards thermometers have no pressure s...

Effects of Heat Treatment on the Inhomogeneity of the Pt/Pd Thermocouple at the Cu Freezing Point

The drift in emf of Pt/Pd thermocouples during successive calibrations at the Cu freezing point was measured. Twelve thermocouples were constructed using wires from a single lot, and a different heat treatment was performed on each thermocouple before the calibration. The purity of the Pt and Pd wires used were 99.999 % and 99.99+ %, respectively. The magnitude of the drift and the inhomogeneity of the thermocouples depended on the heat treatment. The heat treatment at 850 °C or 1030 °C for 100 h resulted in the minimum drift and inhomogeneity.

Johnson Noise Thermometry Based on Integrated Quantum Voltage Noise Source

We performed Johnson noise thermometry (JNT) using an integrated quantum voltage noise source (IQVNS) that generates pseudorandom noise with an RMS value determined by the product of the flux quantum, the clock frequency of IQVNS, fclk, and a calculable coefficient. The working principle is different from the conventional QVNS. The waveform of the IQVNS was analyzed thoroughly, and the source checked to see that it worked properly as intended, particularly in regard to its applicability as a reference for JNT measurements. The thermal noise power of a resistor at the triple point of water was measured with the IQVNS to derive a value of the Boltzmann constant.

Measurement of the Insulation Resistance for the Development of High Temperature Platinum Resistance Thermometers with a Guard Electrode

In the present study, the insulation resistance of insulators within standard platinum resistance thermometers (SPRT) is measured to evaluate the bias in temperature measurements caused by the leakage current flowing through the insulator, and a prototype SPRT to overcome these problems was built. First, a model representing four sources of such leakage has been proposed, and the significance of each source has been estimated quantitatively based on measurements of the insulating resistance. It has also been found that two of the sources can effectively be eliminated by introducing a guard electrode within the SPRT. Based on this result, a prototype of a new design of SPRT equipped with alumina insulators and a guard electrode has been developed. Further measurements showed that the value of the bias agrees well with the model based upon preliminary insulating‐resistance measurements, and the guard electrode could successfully eliminate a bias as large as 37 mK caused by the leakage effect.

Study on the realization of indium point

Indium-point cells were fabricated in NMIJ/AIST using high grade indium samples purchased from some different metal sources. The quality of the indium-point cells were evaluated by conducting temperature measurements during the solid-liquid equilibrium condition, under which the indium fixed-point is defined. Comparisons of fixed-point temperature realized within the cells including the conventional and the newly developed ones were also conducted. The results of these comparisons, termed as direct cell comparisons, as well as the above mentioned temperature measurements under the solid-liquid equilibrium were used to evaluate the effect of impurities to the realization of the indium point. The present paper outlined the cell fabrication, the temperature measurements and the evaluation of impurity effect to the indium point realization.

A wafer surface temperature measurement method utilizing the reordering phenomena of amorphous silicon

In the recent years, the importance of relatively low temperatures ranging from 400degC to 600degC is growing for the rapid thermal processes in semiconductor manufacturing. Measurement and evaluation techniques for the temperature distribution on the wafer surface within the manufacturing equipments are essential. Matsushita Electric Industrial Co., SENCorporation and NMIJ/AIST have done research on a novel temperature measurement method for this temperature region that utilizes the reordering phenomena of amorphous silicon, called the REAL method (Really Exposed Temperature Evaluation Using Reordering of Implanted Amorphous Si Layers). In this paper, we present the principle, the advantages, a trial calculation of the measurement uncertainty and the application of the REAL method

Measurement of Boltzmann constant using superconducting integrated circuit

We have performed measurement of the Boltzmann constant k by Johnson noise thermometry (JNT) using an integrated quantum voltage noise source (IQVNS). IQVNS implemented on a single chip generates calculable pseudo white noise voltages. We have accumulated numerous data of the measurements at the temperature of the triple point of water. At the moment the obtained values of k shows significant difference from the 2014 CODATA value of the order of a few parts in 105.

Development of thermodynamic temperature measurement system based on quantum voltage noise source at NMIJ

We have been developing a Johnson noise thermometer (JNT) at NMIJ toward redefinition of the Boltzmann constant k. The JNT system measure thermal noise power of a resistor installed at the triple point of water and power of a reference signal generated with a Quantum Voltage Noise Source (QVNS) alternatively in order to obtain k precisely. Relative differences between experimentally obtained k and the current CODATA value was 7 part in 10-5. Relative statistical uncertainty of k for 18 hours measurement was 2 parts in 10-5.