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Practical Operation of Cryogen-free Programmable Josephson Voltage Standards



Robert E. Schwall, David Zilz, Jeffrey Power, Charles J. Burroughs, Paul D. Dresselhaus, Samuel P. Benz


Cryogen-free operation is rapidly becoming the preferred implementation of programmable Josephson voltage standard (PJVS) systems. There are strong operational incentives for using the smallest possible cryocooler in order to minimize acoustic noise, system footprint, and power consumption. In addition, Nb/NbxSi1-x/Nb junction technology offers better yield than NbN/TiNx/NbN technology thus making operation near 4K desirable. As junction density increases, however, self-heating of the junctions can create significant thermal gradients and careful design of the overall system is required to maintain acceptable operating margins. We have developed a calorimetric measure-ment technique to characterize the system variables and used it to evaluate several different PJVS configurations. This technique uses the PJVS subarrays as both heat sources and temperature sensors, in conjunction with a time gated measurement techni-que, to characterize the thermal response of the system. Our results suggest that, with appropriate system design, operation of a practical 10V PJVS on a small (nominally 100 mW capacity at 4.2 K) cryocooler is possible.
IEEE Transactions on Applied Superconductivity


Josephson arrays, Quantization, Standards, Superconductor-normal-superconductor devices, Voltage measurement, Superconducting device packaging


Schwall, R. , Zilz, D. , Power, J. , Burroughs, C. , Dresselhaus, P. and Benz, S. (2011), Practical Operation of Cryogen-free Programmable Josephson Voltage Standards, IEEE Transactions on Applied Superconductivity, [online], (Accessed April 14, 2024)
Created February 17, 2011, Updated February 19, 2017