Intercomparison of silicon samples from the Avogadro projects

Abstract

He has been at NIST in various areas since 1962. His principal research interests are precision tests of physical theory, fundamental constants, x-ray and gamma-ray spectroscopy, optical, x-ray and neutron interferometry.

Silicon lattice comparisons related to the Avogadro project: uniformity of new material and surface preparation effects

“…Preliminary comparisons of this sample, which is about 35 mm long, to the WASO17-1 sample show a lattice spacing difference . From these measurements on three WASO17 samples we conclude that the WASO17-1 sample (that has been and is currently being used as a standard on the NIST comparator) is representative of the WASO17 silicon to within and is not the cause of the discrepancy between the PTB and NIST lattice spacing comparisons [2].…”

“…Two ingots of hyperpure float-zoned silicon crystals were produced by Wacker Siltronics specifically for research projects related to an improved determination of the Avogadro constant [2]. The ingots are approximately 165 cm long and 100 mm in diameter.…”

“…The NIST lattice comparison measurements that were reported at CPEM96 were made using crystal samples that were c-m polished [2]. Our experience with polished samples from the new Wacker material suggested that these measurements should be reexamined for potential surface preparation bias.…”

“…7, we compare the PTB relative measurements to the NIST relative measurements for all samples that have been measured at both PTB and NIST. The input data for this figure is given in Tables III and IV of [2], except for the PTB measurement of the NRLM-FZ material, which is given in [3]. All of the original NIST samples were c-m polished and no allowance was made for potential surface preparation bias.…”

Silicon lattice comparisons related to the Avogadro project: uniformity of new material and surface preparation effects

“…7, we compare the PTB relative measurements to the NIST relative measurements for all samples that have been measured at both PTB and NIST. The input data for this figure is given in Tables III and IV of [2], except for the PTB measurement of the NRLM-FZ material, which is given in [3]. All of the original NIST samples were c-m polished and no allowance was made for potential surface preparation bias.…”