Final report on the key comparison EUROMET.BIPM.EM-K10.a: Comparison of Josephson array voltage standards by using a portable Josephson transfer standard

The purpose of this comparison was to compare Josephson voltage standards by using the new VNIIM portable Josephson standard voltage (PJVS) as travelling standard. The comparison was carried out under the auspices of EUROMET (Project 723) from September 2003 to May 2004. It was aimed to link more laboratories organized in EUROMET. In addition, the comparison provides a link between EUROMET, COOMET and the BIPM. Twelve national metrology institutes and the BIPM participated, with the Physikalisch-Technische Bundesanstalt (Braunschweig, Germany) acting as pilot laboratory. The PJVS was accompanied and operated by a VNIIM specialist. The technical protocol requested to measure a 1?V fixed output voltage at an output resistance of 4??, while measurements at 1.2?k? output resistance were optional. The comparisons were performed in a similar way to the new so-called 'option B' bilateral comparisons carried out by the BIPM; the NMIs had to use their own null detector, polarity switch and measurement procedure to measure the output voltage of the PJVS. This method of comparison is more closely related to standard electronic voltage reference (e.g. Zener) measurements but without the limitation to their noise. During all comparisons the PJVS was connected to the same time base as that used by the laboratory Josephson voltage standard. The results demonstrate that the idea of using a portable quantum standard based on a programmable Josephson array as a travelling standard is a powerful tool to achieve equivalence between institutes quickly and at a very good level of uncertainty. Several institutes achieved a relative uncertainty clearly better than one part in 109 at a 95% level of confidence. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the Mutual Recognition Arrangement (MRA).