Josephson Array Voltage Standard Research Articles

Comparison of the Josephson Voltage Standards of the NIST and the BIPM (part of the ongoing BIPM key comparison BIPM.EM-K10.b)

A comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the National Institute of Standards and Technology (NIST), USA, in March 2009. For this exercise, three different measurement methods were carried out: the two different options of the BIPM.EM-K10.b comparison protocol as well as the measurement protocol applied by NIST. The results of both participants are in very good agreement and the overall relative standard uncertainty is 9.5 parts in 1011.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 CIPM Mutual Recognition Arrangement (MRA).

Comparison of the Josephson voltage standards of the LNE and the BIPM (part of the ongoing BIPM key comparison BIPM.EM-K10.b)

A comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the Laboratoire National de Métrologie et d'Essais (LNE), France, in December 2007. The results are in very good agreement and the estimated combined relative standard uncertainty is 1.1 parts in 1011.This comparison is the first to follow the new version of the technical protocols for BIPM.EM-K10a & b (Options A and B1), which were reviewed by the experts designated during the 23rd CCEM (2007) to be members of the CCEM Support Group for BIPM direct on-site Josephson comparisons. The difference with the previous version of the protocol is the insertion of the following rule: "When a significant improvement is obtained during the comparison both the initial and the final results are added to the KCDB with a note, but only the final result appears on the graph of results."This article describes the technical details of the experiments which were carried out to achieve the final result of the comparison.1 Option A is the scheme where the BIPM measures the JVS of the participant with its measurement setup. Option B is the other way around.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 CIPM Mutual Recognition Arrangement (MRA).

Comparison of the Josephson Voltage Standards of the KRISS and the BIPM (part of the ongoing BIPM key comparison BIPM.EM-K10.b)

As a part of the ongoing BIPM key comparisons BIPM.EM-K10.b, an on-site, direct comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the Korea Research Institute of Standards and Science (KRISS), Republic of Korea, in February 2008.The final result of the comparison is presented as the difference between the value assigned to the transportable 10 V BIPM Josephson Voltage Standard by the KRISS, at the KRISS, to the theoretical value assigned to the BIPM Josephson Voltage Standard: (UKRISS − UBIPM)/UBIPM = +1.7 × 10−10 and uc/UBIPM = 1.3 × 10−10 where uc is the relative combined standard uncertainty associated with the measured difference, including the uncertainty of the representation of the volt at the BIPM, the uncertainty of the representation of the volt at KRISS, both based on KJ-90, and the uncertainty related to the comparison.The results are in very good agreement and show that the primary voltage standards maintained by the KRISS and the BIPM were equivalent, within their stated expanded uncertainties.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 CIPM Mutual Recognition Arrangement (MRA).

Bilateral direct comparison of Josephson array voltage standards of the PTB (Germany) and PEL (Croatia): Draft B report for EUROMET.EM-S28

A comparison of the 10 V Josephson array voltage standard of the Physikalisch-Technische Bundesanstalt (PTB), Germany, was made with that of the Primarni Elektromagnetski Laboratorij (PEL), Croatia, in April 2007. The results are in very good agreement and the measured overall relative combined standard uncertainty is better than 1 part in 1010.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 EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Limits to the Accuracy of 10-V Josephson Standards Revealed by BIPM On-Site Comparisons

In September 2004, the Bureau International des Poids et Mesures (BIPM) began a new round of its large-scale international comparison of Josephson array voltage standards with national metrology institutes. As an option, it offers a new simplified measurement procedure, whereby the other participants simply measure the BIPM array as if it were an electronic voltage standard. This presentation discusses the accuracy of JAVS, the problems that were encountered in the new round, and how most of them were resolved

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 Ω, while measurements at 1.2 kΩ 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).

Accuracy of a Cryocooler-Based Programmable Josephson Voltage Standard

A cryocooler-based programmable Josephson array voltage standard (JAVS) for 4-K operation and a very compact microwave source are described. Both components are crucial for future mobile voltage standards. A direct comparison between two programmable JAVS using these components was performed at 1 V in order to test whether these systems are suitable for metrological application at the highest level of precision. The results of the comparison show that the new components are suitable for mobile JAVS with an uncertainty of less than 1 /spl times/ 10/sup -9/.

VNIIM–PTB comparison using a portable Josephson voltage standard

The Josephson array voltage standards (JVSs) of the VNIIM and the PTB were compared using a new portable JVS (PJVS) as travelling standard. The PJVS which uses a 1 V programmable superconductive–insulator–normal–insulator–superconductive Josephson array is described in detail. The results of the comparison show that the new PJVS is suitable for comparisons and verifications of laboratory JVS with an uncertainty of less than 1×10−9.

Accurate measurements of quantum voltage steps on arrays of bicrystal Josephson junctions

Quantum voltages of an array of YBa2Cu3O7 bicrystal junctions were calibrated against a programmable Josephson array voltage standard. We demonstrated that steps of the current–voltage characteristic of an array of bicrystal junctions at voltages of about 9 mV were flat over the current range of about 80 μA to within six parts in 108. The coincidence of quantum voltages on the array of high-temperature superconductor junctions at 64 K and the reference voltage on the array of niobium junctions at 4.2 K was measured with an uncertainty of two parts in 108. With the same uncertainty, we revealed the coincidence of the Josephson constant KJ≡h/2e in YBa2Cu3O7 and in metallic superconductors.

Indirect comparison of 10 V Josephson array voltage standards between the UME and the BNM-LCIE

The results of a bilateral comparison of 10 V Josephson array voltage standards of the Ulusal Metroloji Enstitüsü (TÜBTAK-UME, Turkey) and the Bureau National de Métrologie-Laboratoire Central des Industries Électriques (BNM-LCIE, France), in the framework of EUROMET Project No. 469, are reported. A set of four Zener-diode-based voltage reference standards (Fluke 732B), delivered by the UME, was used as a transfer standard between the two laboratories. The results show an agreement within 97 nV with an overall uncertainty (1 σ) of 98 nV.

Comparison of the Josephson voltage standards of VNIIM and PTB

Comparisons of the 1 V Josephson array voltage standard (JAVS) of the D.I. Mendeleyev Institute for Metrology (VNIIM), Russia, with that of the Physikalisch-Technische Bundesanstalt (PTB), Germany, were carried out in St. Petersburg in June 1999. The results of the direct comparison agree within an overall standard uncertainty of less than 1 nV. The results also show that direct comparisons are useful for detecting voltage offsets of a few parts in 10/sup 10/. The reason for a small voltage offset in an SIS array was investigated at zero voltage level.

Using power spectra and Allan variances to characterise the noise of Zener-diode voltage standards

The differences between the voltage outputs of Zener-diode based electronic voltage standards (Zeners) and standard cells, between Zeners and a Josephson array voltage standard (JAVS) and between pairs of Zeners are measured. The data are analysed as time series. They are serially correlated so that the use of the usual expression for the standard deviation of the mean, the experimental standard deviation divided by the square root of the number of measurements, to characterise the dispersion is not justified. Noise in Zeners is of a 1/f nature and is characterised by using the power spectral density and Allan variance, a statistic used in time and frequency metrology. The uncertainty in the measurements of the 10 V outputs of 13 Zeners is limited by 1/f noise to a ‘floor’ value ranging between two parts in 109 and eight parts in 109 of the nominal output value. Methods are proposed for estimating the Allan variance of a Zener using either a standard cell, a JAVS, or a small group of similar Zeners.

Mathematical model to approximate the response of a Zener cell output under varying environmental conditions

Fifteen national and territorial metrology institutes in the Asia-Pacific region have taken part in a comparison of dc voltage coordinated by the National Measurement Centre of the Singapore Productivity and Standards Board. A Zener cell was used as the travelling standard in the comparison. A mathematical model based on a first-order differential equation is developed to describe the influence of time, temperature, and humidity on the Zener voltage. The results of comparisons with Josephson array voltage standards (JAVSs) in seven different laboratories agree well with data predicted by the model.

Using 10 V Josephson voltage standards to estimate the uncertainty of Zener voltage references as traveling standards

In anticipation of a European comparison of 10 V Josephson array voltage standards (EUROMET project 429 led by the NMi VSL), the BIPM and the BNM-LCIE Josephson standards have been compared by means of Zener traveling references. A mean difference of 5 parts in 10/sup 9/ has been found with a standard uncertainty of 6 parts in 10/sup 9/. The results show that the performance of the Zener references could be the main cause of uncertainty in such a comparison.

Comparison of the Josephson voltage standards of the CEM and the BIPM

Comparisons of the 1 V Josephson array voltage standard of the Bureau International des Poids et Mesures were made with that of the Centro Espanol de Metrologia, Madrid (Spain), in October 1997. The results agree within an overall standard uncertainty of less than 1 nV.

Comparison of the Josephson voltage standards of the IEN and the BIPM

Comparisons of the 1 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) were made with that of the Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), Turin, Italy, in November 1996. The results agree within an overall uncertainty of less than 1 nV.

Comparison of Josephson array voltage standards using Zener reference standards

The Josephson array voltage standard at the Beijing Institute of Radio Metrology and Measurement (BIRMM) has been used in China to realize the volt since 1992. In order to verify the accuracy and reliability of the voltage standard at the BIRMM, a comparison of the Josephson array voltage standards at 1,018 V and 10 V between the BIRMM, the Danish Institute of Fundamental Metrology (DFM) and the National Physical Laboratory (NPL), UK, has been performed. Two Zener reference standards were used to transfer the voltage between the three laboratories. The results show a difference of less than 2 × 10-8.

Comparison of the Josephson voltage standards of the SP and the BIPM

Comparisons of the 1 V Josephson-array voltage standard (JAVS) of the Bureau International des Poids et Mesures (BIPM) were made with that of the Swedish National Testing and Research Institute (SP), Boras, Sweden, in April 1996. The results agree within an overall uncertainty of less than 1 nV.

Comparison of the Josephson voltage standards of the NIM (China) and the BIPM

Comparisons of the 1 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) were made with that of the National Institute of Metrology (NIM), Beijing, China, in November 1995. The results agree within an overall uncertainty of less than 1 nV.

Comparison of Josephson voltage standards held by the SISIR and the DFM

We have compared the Josephson array voltage standard (JAVS) held by the Singapore Institute of Standards and Industrial Research (SISIR) with that of the Danish Institute of Fundamental Metrology (DFM). The comparison took place in Singapore from 20-25 March 1995. A commercial Zener reference voltage standard was used as transfer instrument between the two laboratories. The result of the comparison was an observed difference of 13 nV with a combined uncertainty of 9 nV. The difference was independent of several measurement configurations used.