Compact DC Josephson Voltage Standard

This paper presents precision measurements with a prototype cryogen-liquid-free DC Josephson voltage standard that produces a 1 V maximum output. Its cryostat is sufficiently compact that it can be operated on a bench close to devices under test. Compared to the National Institute of Standards and Technology (NIST) programmable Josephson voltage standard (PJVS), this bench-top Josephson voltage standard (BJVS) has a smaller cryostat (only 25 % of the volume), the Josephson junction array circuit is less complex and has only 10 % as many junctions, simpler bias electronics, and reduced mechanical cooling requirements. Direct voltage comparison between the BJVS and the PJVS achieved a relative agreement of 5 x 10(-10) at 1 V. With the recent redefinition of the International System of Units (SI), the BJVS becomes a primary realization the unit volt, requiring only access to a standard single-phase power outlet and a GPS signal (SI second).