A bias source for dynamic voltage measurements with a programmable Josephson junction array

In this paper, the design and test of a compact bias current source for binary-weighted programmable Josephson junction arrays (PJJA) is reported. The new source, driven by a Linux-based real-time controller, enables continuous PJJA updates at a rate greater than 10 kHz. Fast and accurate voltage measurements by null detection against the PJJA are possible, owing to an onboard analog-to-digital converter (ADC). The new source will be used in Watt-balance experiments at the Laboratoire National de Metrologie et d'Essais (LNE) and the National Physical Laboratory (NPL) to perform dynamic measurement of the coil voltage during the dynamic phase.