The influence of the contact resistance of the interface of the YBCO/Au structure on the transport and microwave properties of arrays of high-temperature bicrystal Josephson junctions embedded in a coplanar transmission line has been studied. The current-voltage characteristics of Josephson structures fabricated using various technologies are studied: in situ and ex situ with annealing in an oxygen atmosphere. The results obtained can be used to create a quantum ac voltage generator based on high-temperature Josephson junctions. Keywords: high-temperature superconductors, Josephson junctions, microwave, contact resistance.

The influence of the contact resistance of the interface of the YBCO/Au structure on the transport and microwave properties of arrays of high-temperature bicrystal Josephson junctions embedded in a coplanar transmission line has been studied. The current-voltage characteristics of Josephson structures fabricated using various technologies are studied: in-situ and ex-situ with annealing in an oxygen atmosphere. The results obtained can be used to create a quantum ac voltage generator based on high-temperature Josephson junctions.

The principles for building the multivalued N4-21 voltage standard based on the precision properties of Zener diodes and the quantum mechanical properties of high-temperature superconductor Josephson junctions operating at 77 K are discussed. The metrological characteristics of the new voltage standard are presented. The relative uncertainty in the output voltages of the standard at 1 and 10 V is found to be less than 5·10–8.

A commercially available Josephson voltage standard based on high temperature superconductor Josephson junctions with a liquid nitrogen free cooling is presented. The results of the calibrations of an electronic DC reference Fluke 732B and a Keithley nanovoltmeter 2182 with uncertainties equal to a few parts in 108 demonstrate the suitability of the application of a N4-21 in the highest-level metrology. The implementation of a link between Josephson junctions and Zener diodes largely eliminates the uncertainty contributions associated with Zeners non-linear drift, environmental effects and the impact due to shipping.

A practical dc voltage standard with output voltages Ł/hts from 0.1 V to 10 V using high temperature superconductor (HTS) arrays of Josephson junctions cooled to 77 K was characterized. HTS arrays with increased current margins and the voltage divider with a high stability of the divider's coefficients enable stable and reproducible automated calibration of the new HTS standard. The direct comparison of U HTS against the voltage generated on an array of niobium Josephson junctions cooled to 4.2 K reveals the agreement of voltages at 1 V level with a Type A uncertainty equal to a few parts in 10 8 .

We are using a quantum dc voltage generated on an array of high-temperature superconductor junctions in the developed voltage standard with an output voltage up to 10 V. In the abstract the concept and main parts of this instrument are presented.

Increasing the working voltage across chains of josephson junctions is considered during operation. (AIP)