Optimized 1 V and 10 V Josephson series arrays

Using a modified fabrication method and a detailed design investigation we have been able to optimize the array circuits for the Josephson voltage standard and to solve the trapped flux problem. Even in very long arrays (4800 junctions in a single stripline) a yield of 1 mV per junction could be achieved. The microwave power in the range from 70 GHz to 73 GHz required for stable operation of 1 V and 10 V circuits could be reduced to approximately 1 mW and 10 mW (antenna input), respectively. The best results at 10 V were obtained with circuits of 13 924 junctions arranged in 4 microwave paths connected in parallel. Excellent calibration conditions were maintained for current densities of about 10 A/cm/sup 2/ for which the ratio of operating frequency to plasma frequency is increased to six.