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Lumped 50 Ohm Arrays of SNS Josephson Junctions



Nicolas Hadacek, Paul Dresselhaus, Samuel Benz


For the first time lumped series arrays of Josephson junctions have been fabricated with a transmission line-matched 50 Ohm nresistance and having the thousands of junctions necessary to produce a metrologically significant voltage. Using such arrays we hoped to increase the output voltage per array and to optimize their performance for Josephson voltage standards. Traditional Josephson arrays for voltage standards have used distributed microwave structures, where array lengths are many multiples of the driving wavelength. The lumped arrays in this work have physical lengths shorter than a quarter of the microwave drive wavelength and total normal-state resistances nearly equal to the transmission line impedance. Fabrication of these arrays was made possible using the newly developed Nb-(MoSi2-Nb)n stacked junction technology. We present measurements of the microwave response of a number of lumped arrays with total normal resistances up to 54 Ohms and with various resistances terminating the transmission line. A simple numerical model is presented that accounts for the spatial distribution of the microwave current and for the non-uniformity of the junction critical currents. The resulting simulations are in good agreement with measurements of the current range of constant voltage steps.
IEEE Transactions on Applied Superconductivity


Josephson arrays, lumped array, superconductive electronics, Voltage standard


Hadacek, N. , Dresselhaus, P. and Benz, S. (2006), Lumped 50 Ohm Arrays of SNS Josephson Junctions, IEEE Transactions on Applied Superconductivity, [online], (Accessed April 20, 2024)
Created November 30, 2006, Updated October 12, 2021