Conventional Josephson Voltage Standard Research Articles

Application of a 10 V Programmable Josephson Voltage Standard in Direct Comparison With Conventional Josephson Voltage Standards

This paper briefly describes the working principle of the 10 V programmable Josephson voltage standard (PJVS) that was developed at the National Institute of Standards and Technology and how to use it in a direct comparison with a conventional Josephson voltage standard (CJVS). Manual and automatic comparison methods were developed to verify the agreement between the two types of Josephson standards. A 10 V PJVS provided by the National Aeronautics and Space Administration (NASA) was used as a transfer standard in the 2014 Josephson voltage standard Interlaboratory Comparison that is organized by the National Conference of Standards Laboratories International. The results of automatic direct comparisons between a NASA PJVS and three CJVSs are reported. Allan variance is applied to analyze the large number of correlated data for Type A uncertainty.

The 2014 North American Josephson Voltage Interlaboratory Comparison

Abstract:The 10th North American Josephson voltage standard (JVS) interlaboratory comparison (ILC) at 10 V was completed in 2014. This ILC was unique because it consisted of two parts. An on-site comparison was conducted between the National Institute of Standards and Technology (NIST) transportable JVS and the pivot laboratory's conventional JVS (CJVS) system. A set of four traveling Zener voltage standards then served to transfer traceability from the pivot laboratory to the 12 other participants. In addition to the regular ILC activities, a second on-site comparison was conducted between the NIST transportable JVS and the programmable JVS (PJVS) provided by the National Aeronautics and Space Administration (NASA). Due to limited availability of the PJVS, only two laboratories were selected to make direct comparisons between their CJVS systems and NASA's PJVS. The method has been used for the first time in the JVS ILC and has the advantage of using the PJVS as a transfer standard. This allowed the parti...

A 10 V programmable Josephson voltage standard and its applications for voltage metrology

The concept of a programmable Josephson voltage standard (PJVS) was first proposed in 1997. Since then a significant amount of research and development work has been devoted to the fabrication of the programmable Josephson junction array and its deployment in a voltage standard system. This paper reports the recent development of a 10 V PJVS system at the National Institute of Standards and Technology (NIST) and its voltage metrology applications. The superior stability of the voltage step of the new 10 V PJVS enables it to perform the same tasks as the conventional Josephson voltage standard (JVS) that uses hysteretic voltage steps and to improve the efficiency and effectiveness of a JVS direct comparison. For the first time, a comparison between a conventional JVS and the NIST 10 V PJVS was performed in order to verify the performance of the NIST 10 V PJVS. The mean difference between the two systems at 10 V was found to be −0.49 nV with a combined standard uncertainty of 1.32 nV (k = 1) or a relative combined standard uncertainty of 1.32 parts in 1010. Automatic comparisons between the 10 V PJVS and a 2.5 V PJVS at 1.018 V were performed to monitor the long term accuracy and stability of the 2.5 V PJVS and to support the NIST electronic kilogram experiment. By matching the voltages of the two PJVS systems during a comparison, the type B uncertainty can be minimized to a negligible level. The difference between the two PJVS at 1.018 V was found to be −0.38 nV with a combined standard uncertainty of 0.68 nV (k = 1) or a relative combined standard uncertainty of 6.7 parts in 1010. Issues encountered during the PJVS comparison and potential challenges for 10 V applications are also discussed.

A direct comparison of a 10 V Josephson voltage standard between a refrigerator-basedmulti-chip programmable system and a conventional system

A multi-chip 10 V programmable Josephson voltage standard (PJVS) systemwas demonstrated using a closed-cycle refrigerator. We precisely measured thePJVS by a direct comparison measurement with a conventional Josephsonvoltage standard. The result agreed within a combined standard uncertainty of3.9 × 10−10 at 10 V.

10 V SINIS Josephson junction series arrays for programmable voltage standards

A programmable dc voltage standard for output voltages of up to 10 V has been realized. The series arrays, consisting of about 69120 overdamped superconductor/insulator/normal metal/insulator/superconductor (SINIS) Josephson junctions, have been fabricated using the reliable Nb-Al/Al/sub 2/O/sub 3/ technology. The arrays can be operated in conventional Josephson voltage standards at microwave frequencies from 70 GHz to 75 GHz. Steps of constant voltage are observed at very low microwave power levels, since the major part of the microwave power is generated by the junctions themselves. The operation of the arrays and the formation of Shapiro steps are discussed.

1 volt DC programmable Josephson voltage standard

NIST has developed a programmable Josephson voltage standard (JVS) that produces intrinsically stable voltages that are programmable from -1.1 V to +1.1 V. The rapid settling time (1 /spl mu/s), large operating current margins (2 to 4 mA), and inherent step stability of this new system make it superior to a conventional JVS for many dc measurements. This improved performance is made possible by a new integrated-circuit technology using intrinsically shunted superconductor-normal-superconductor (SNS) Josephson junctions. These junctions operate at lower excitation frequencies (10 to 20 GHz) than a conventional JVS and have 100 times greater noise immunity. The Josephson chip consists of a binary array sequence of 32 768 SNS Josephson junctions. The chip has been integrated into a completely automated system that is finding application in mechanical/electrical watt-balance experiments, evaluation of thermal voltage converters, electron-counting capacitance standards, and metrology triangle experiments.

Stable 1 volt programmable voltage standard

Several fully functional programmable voltage standard chips, each having a total of 32 768 Nb–PdAu–Nb Josephson junctions, have been fabricated and tested. The chips are based on a new design that provides fast programmability (1 μs) between voltages and stable voltage operation from −1 to +1 V. A comparison of the new standard with a conventional Josephson voltage standard is in agreement to 0.5±1.1 parts in 109. We demonstrate the utility of this standard by measuring the linearity of a digital voltmeter.