AC Josephson voltage standard: Progress report

Progress toward a Josephson voltage standard for fast de measurements and accurate ac waveform synthesis is described, A superconductor-normal-superconductor (SNS) junction process is used to make 5 mA critical current arrays with up to 32 768 junctions, With rf excitation at 11 GHz these arrays generate milliampere constant-voltage steps, A bias control circuit that provides output current amplification, transient suppression, and submicrosecond settling time is used with both superconductor-insulator-superconductor (SIS) and SNS junction arrays for fast, automated measurements of A/D converter linearity, a test for subnanovolt accuracy, waveform synthesis, and a preliminary measurement of the ac-dc difference of a thermal voltage converter.