ONE-DIMENSIONAL PARALLEL JOSEPHSON-JUNCTION ARRAYS AS A TOOL FOR DIAGNOSTICS

We propose and demonstrate the use of underdamped, one-dimensional parallel arrays of Josephson junctions as a tool for circuit diagnostics. By measuring the Fiske modes and the critical current in a magnetic field, we determined the self- and nearest-neighbor inductances as well as the capacitances of single junctions. We have used this technique to find the capacitance of capacitances of single junctions. We have used this technique to find the capacitance of Nb-Al2Ox-Nb junctions for critical current densities of 0.3-20 kA/cm2. We find that the specific capacitance increases by about a factor of 2 over this range. This increase has important consequences for the design of single-flux-quantum circuits and SQUIDs. Measurement of the junction capacitance for critical current densities of 100 kA/cm2 is possible, but requires submicrometer junctions with dimensions of the order of 0.3 mum. (C) 1994 American Institute of Physics.