One-Dimensional Parallel Josephson-junction Arrays as a Tool for Circuit 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 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 SQUID's. Measurement of the junction capacitance for critical current densities of 100 kA/cm2 is possible, but requires submicron junctions with dimensions of the order of 0.3 µm. © 1995 IEEE