1 volt DC programmable Josephson voltage standard

Abstract

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.