STACKED NIOBIUM JOSEPHSON-JUNCTION ARRAYS UNDER X-BAND IRRADIATION

Stacked Josephson junction arrays located at the rf current antinodes of a superconducting microstripline resonator were investigated. The c ircuits were designed to obtain highly accurate voltages at cm-waveban d microwave driving and low rf-power level. Nb-Al/AlOx-Nb Josephson ju nctions with tunneling area of 60 mu m x 300 mu m and critical current density up to 7A/cm(2) were used. We compared the average voltages of the rf induced maximal current steps in arrays with up to three junct ions per stack. Quantized current steps up to 300 mV were observed und er microwave irradiation at frequency of 19.20 GHz in circuits with 38 4 three-junction stacks. The dynamics of stacked tunnel junctions in t he presence of rf-currents will be discussed with respect to applicati on as voltage standards.