Toward the Avogadro constant-preliminary results on the molar volume of silicon

Progress on accurate measurement of the Planck constant: Watt balance and counting atoms

“…13(a). [106] Later a two-optical-interferometer system was developed at INRIM [107] and NMIJ, [108] as shown in Fig. 13(b), in which the reflected light from the sphere was collimated by a lens to overcome the problem due to the diffraction of the reflected light in Saunders' interferometer.…”

Progress on accurate measurement of the Planck constant: watt balance and counting atoms

“…The first measurement for precision determination of the sphere volume was taken at NIST by an optical interferometer which was designed by Saunders and shown in figure 13(a) [106]. Later a two-optical-interferometer system was developed at INRIM [107] and NMIJ [108] as shown in figure 13(b), in which the reflected light from the sphere was collimated by a lens to overcome the problem due to the diffraction of the reflected light in Saunders' interferometer [109]. At PTB, a Fizeau interferometer with a spherical etalon was developed shown in figure 13(c) [110] with an advantage in analysing the entire surface of the sphere [111].…”

Primary calibration of the volume of silicon spheres

“…After the development of the polishing techniques for silicon spheres at the CSIRO, Australia, in the 1980s [11,12], optical interferometers with flat reference plates have been developed at the Istituto di Metrologia 'G Colonnetti' (IMGC), Italy [29][30][31][32], the National Metrology Institute of Japan (NMIJ, formerly the National Research Laboratory of Metrology) [33][34][35][36][37][38][39] and the CSIRO [40].…”

“…Furthermore, this design enables us to measure the two gaps, d 1 and d 2 , simultaneously so that any mechanical instability in the position of the sphere relative to that of the etalon can be cancelled completely. At the IMGC, an optical interferometer with a flat etalon and a spherical wave was used [29][30][31][32], as shown in (c), in which the effect of diffraction was also removed.…”

“…At the NMIJ, the diameters of two silicon spheres prepared from the same silicon crystals, S4 and S5, were measured at 22.5 • C and 0 Pa [38,39]. Since the correction for the thermal expansion is rather large, their density values at 20 It is known that the difference in their density values exactly corresponds to the difference in isotopic compositions of 28 Si, 29 Si and 30 Si [36], and the density difference was already confirmed by differential density measurements, such as hydrostatic weighing and the pressure-of-flotation method [65,66].…”