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The new definition of the kilogram based on the Planck constant was implemented in May 2019. The National Metrology Institute of Japan (NMIJ) will realize the new kilogram by the X-ray crystal density method using a 28Si-enriched sphere. An international comparison of the realizations of the new kilogram by national metrology institutes was organized. As a participant in the comparison, the NMIJ realized the kilogram by the volume measurement and surface characterization of a 28Si-enriched sphere. Details of the measurement results and the uncertainty evaluation of the realization are described. The comparison of the realization results with previous realization results in 2016 is also provided.

The precision measurement of radiation pressure force, especially in a manner traceable to the International System of Units (SI) is of importance. For the precision measurement of radiation pressure of optical laser, a voltage balance which uses electrostatic force between electrodes has been developed at the National Metrology Institute of Japan (NMIJ). The voltage balance enables mass and force measurements traceable to the new definition of the kilogram. To confirm the reliability of the balance, the mass of a 2 mg wire weight was determined. The relative standard uncertainty of the mass measurement was estimated to be $8.4\times 10^{-4}$ . The mass of the weight was also measured by a commercially available electronic balance. The masses determined by the two different methods were in agreement within their uncertainties. Details on the measurement system and result are presented.

For establishing a new calibration method for small mass and force based on a new definition of the kilogram, the SI traceable measurement method which uses the electrostatic force balance was developed. Small mass was measured by comparing the gravity force acting on the small object and the electrostatic force which can be calibrated by using the electrical standards. New technical approaches such as monolithic flexure hinge for balance mechanism and double equal capacitor system for electrical control were applied. Weighing of a 2 mg stainless steel weight was performed. In the measurement, there was deviation from the nominal value of the weight, which was caused by the thermal drift and surface charge. Details on the measurement apparatus and the experiment results are presented.

For the determination of the Avogadro constant via the XRCD-method the ratio of two temperature-dependent quantities, the unit cell volume and the sphere volume, need to be measured with the smallest possible uncertainties. Since both quantities show the same temperature dependency, only the reproducibility of the temperature measurements has to be taken into account. This paper summarizes the test measurements made for determining the accuracy of the temperature measurements of the standard platinum resistance thermometers which are used in the measurements of the silicon-lattice parameter at the INRIM and PTB, and the volume, at the NMIJ and PTB.

To determine the Avogadro constant by the International Avogadro Coordination using the x-ray crystal density method, the volume of a28Si-enriched sphere, named Si28kgOla, was measured at NMIJ. The volume was determined from the diameter measurement in 2175 directions by an optical interferometer. Taking into account the results of the surface characterization of the sphere by x-ray photoelectron spectroscopy and spectroscopic ellipsometry, the volume of the Si core excluding the surface layers was determined with a relative uncertainty of $\pmb{2\ \times\ 10^{-8}}$ . Details of the interferometer and the uncertainty analysis of the volume measurement are presented.

For the determination of the Avogadro constant using the x-ray crystal density method, surface analysis of Si spheres is essential. The difference of the surface layer thickness in vacuum and in air conditions was investigated by ellipsometry. In order to estimate the effect of vapor adsorption on the determination of the thickness of the surface layer of Si spheres, an ellipsometer with vacuum chamber and vapor controlling system is proposed.

In the future realization of the kilogram using the x-ray crystal density method, isotopically enriched silicon crystals grown by the floating zone method are employed. In this paper, we present the electron paramagnetic resonance study on 28Si single crystal AVO28. We revealed that the concentrations of various kinds of vacancy defects in the crystal are less than ${1\times 10^{12}}\text{cm}^{-3}$ . Consequently, the necessary mass deficit correction due to these vacancy defects is estimated to be less than ${0.4} \mu \text{g}$ for 1 kg AVO28 spheres.

The Avogadro constant is determined accurately by applying the x-ray crystal density method to 28Si-enriched spheres, which is one of the practical methods for the kilogram redefinition. In this paper, we present the results of mass measurements of 28Si-enriched spheres, performed at NMIJ in 2014 for the determination of the Avogadro constant. The results of reproducibility of the cleaning effects on the mass of the spheres together with the influence of the BIPM Extraordinary Calibrations, are shown. With these achievements, NMIJ plans to participate in the Pilot Study aiming at the kilogram redefinition, where the mass measurements play an important role.

The homogeneity of the lattice spacing of silicon single crystals was characterized by the self-referenced lattice comparator. Lattice strain measurements were performed on single crystals from 28Si ingot (Avo28), which was used to determine the Avogadro constant. A curved and layered pattern was observed for the sample of 10.5 cut from the tail-side of the Avo28 ingot. The homogeneity of the lattice constant of the Avo28 was discussed.

For the new definition of the kilogram, surface analysis of Si spheres is essential to determine the Avogadro constant by using the x-ray crystal density method. In this work, to investigate surface characteristics of Si spheres both in vacuum and in air, a new ellipsometer having a vacuum chamber was developed. This ellipsometer enables accurate determination of the density of 28Si-enriched spheres.

Surface layer characterization is crucial for high-accuracy determination of the Avogadro constant by using 28Si enriched spheres for redefinition of the kilogram. In this work, we carried out the thickness measurements of the oxide and carbonaceous layer on a 28Si-enriched sphere by x-ray photoelectron spectroscopy (XPS) for a pilot study to confirm the international equivalence of the ability to realize the kilogram from the new definition. A sphere rotation mechanism was installed into the XPS system to measure the thickness at different points on the surface. The average thickness and uncertainty budget of the oxide and carbonaceous layers were evaluated.

A change in the definition of the kilogram has been proposed. The new definition will be based on the Planck constant. After the change, the National Metrology Institute of Japan (NMIJ) will realize the kilogram using the X-ray crystal density method with a 28Si-enriched sphere. A pilot study to confirm the international equivalence of the ability to realize the kilogram from the new definition is ongoing, where the volume measurement of a 28Si-enriched sphere by optical interferometry and the sphere surface characterization by spectroscopic ellipsometry and X-ray photoelectron spectroscopy required for the realization were performed by NMIJ independently. The mass of the sphere was determined with a relative standard uncertainty of $2.4\times 10^{\mathrm {\mathbf {-8}}}$ based on the new definition. This paper provides details of the measurements, the data analysis, and the uncertainty evaluation.

In the determination of the Avogadro constant using the x-ray crystal density method, volume measurements of Si spheres by optical interferometry play a crucial role. For the accurate volume determination, geometrical shape of the optical components of the interferometer has been evaluated by using ray-tracing method. To reduce the noise in the interference fringes, a new etalon has been developed. An optical frequency comb has been also introduced in the interferometer as the optical frequency standard for more reliable and precise volume measurement. Details of the improvements are described.

We propose a way to reuse obsolete older model PCs as a grid in keeping with green IT. A grid can create a high performance environment consisting of ordinary PCs. However, it has continuous energy requirements. This is undesirable in terms of environmental concerns, because of the increased CO2 emissions from generating the required electricity. Therefore, this study aimed at realizing a grid powered using solar power to overcome the disadvantage, while reusing obsolete older model PCs. If it keeps up bad weather, the system may stop because solar panel can't generate electricity plentifully. The reboot feature reboots the system when the system's batteries charge from empty electricity capacity to sufficient electricity capacity. We have implemented the reboot feature on the system and experimented in this paper.

In keeping with green IT, we propose reusing obsolete older-model PCs as a grid to create a high performance environment consisting of ordinary PCs. However, such a grid has continuous energy requirements, which is undesirable in terms of environmental concerns, due to the increased CO2 emissions from generating the required electricity. Therefore, this study aims to realize a grid powered by solar power to overcome the disadvantage, while reusing obsolete older model PCs. In this paper, we propose a means of operating a grid system powered by photovoltaics using weather reports to operate the system effectively and validate the proposal through simulations.

In this paper, we propose a way to reuse obsolete older model PCs as a grid in keeping with green IT. A grid can create a high performance environment consisting of ordinary PCs. However, it has continuous energy requirements. This is undesirable in terms of environmental concerns, because of the increased CO2 emissions from generating the required electricity. Therefore, this study aimed at realizing a grid powered using solar power to overcome the disadvantage, while reusing obsolete older model PCs. We studied we measured outdoor operating time of the system using only a master node PC using our new power management method. We operated this system, which was composed of three reused PCs, outdoors. We found an efficient charging method that can be used during system operation, and were able to identify priorities for future work.

We propose a way to reuse obsolete older model PCs as a grid in keeping with Green IT. A grid has the advantage of creating a high performance environment consisting of ordinary PCs. However, it has the disadvantage of always requiring electricity, which is undesirable for the global environment due to the increased CO2 emissions from generating electricity. Therefore, this study proposes a grid powered by solar power to solve the disadvantage while at the same time reusing obsolete older model PCs.

This paper reports the progress and the achievements of an international research project aimed at determining the Avogadro constant by counting the atoms in enriched 28Si spheres.

The density of an isotopically enriched 28Si crystal is evaluated. A transfer standard of the hollow silicon cylinder is prepared and its density is determined by the hydrostatic weighing (HW). The 28Si crystal is then compared with the hollow silicon for the determination of the density by the pressure-of-flotation (PF) measurement.

The present status of an international attempt of several national metrology institutes to determine the Avogadro constant with a relative standard uncertainty better than 2ldr10-8 is presented. To this end, a world-wide collaboration has been set up to produce a 5 kg 28Si single crystal with an enrichment factor greater than 99.985%. Technological steps for the growth of the 28Si single crystal, manufacturing of two 1 kg 28Si spheres, and first experimental results are reported.

The results of density difference measurements by the flotation apparatuses of NMLJ and PTB for four silicon samples are reported. The flotation method is used to investigate the inhomogeneity and to determine the absolute density of silicon crystals for the determination of the Avogadro constant

A determination of the Avogadro constant from two selected silicon single-crystals with natural isotopic compositions is described. The density, molar mass, and lattice spacing of the two crystals were measured at NMIJ, PTB, IRMM, IMGC, and NIST. When all the data are combined, they lead to a value of the Avogadro constant of 6.022 1353 (18)/spl times/10/sup 23/ mol/sup -1/ with a relative combined standard uncertainty of 3.1/spl times/10/sup -7/.

For a determination of the Avogadro constant N/sub A/ by the X-ray crystal density (XRCD) method, the molar volume M//spl rho/ of three different silicon crystals, NRLM1, NRLM2, and NRLM4, have been analyzed systematically by measurements of their densities /spl rho/ and molar masses M. Details on the sample preparations and the result of measurement are presented.

The systematic errors for the determination of the Avogadro constant using a FZ silicon ingot for NRLM are analyzed by studying the silica layer on the surface, macroscopic and microscopic defect in the body, of the sphere and concluded Avogadro constant shows the discrepancies around 3ppm to previously reported numbers.

In order to obtain a more accurate value for the Avogadro constant N/sub A/ the reliability of density values obtained by different measuring techniques for silicon single crystals was checked by density determinations with four silicon spheres at PTB, IMGC, and NRLM. The diameters of the spheres (two of PTB and two of NRLM) ranged from 90 mm to 94 mm. All the mass measurements (at PTB, IMGC, and NRLM) were carried out in air. At IMGC and NRLM the volume was determined by interferometric measurements, whereas at PTB the volume was obtained from hydrostatic weighings using two Zerodur volume standards. In addition, at PTB the densities of the four spheres were cross-checked by flotation measurements. The maximum relative density difference was found to be 1/spl times/10/sup -6/, whereas the typical values were 2/spl times/10/sup -7/.

Considerable improvements in the measurements of the molar mass M(Si) of silicon crystals combined with high-accuracy densities (/spl rho/) of the same crystals, have yielded experimental M(Si)//spl rho/ values resulting from the PTB-IRMM, the IMGC-IRMM and the NRLM-IRMM projects for the redetermination of Avogadro's Constant. These M(Si)//spl rho/ values are compared with attributed uncertainties, in relation to the supposition of constancy M(Si)//spl rho/ for silicon. >