Current Limitation Characteristics of Josephson Junction Array

A current limiter was manufactured using a Josephson junction array to cut off an excessive current flowing into the SQUID sensor. The Fabricateed Josephson junction array was connected in series with a flux transformer that consists of a pick-up coil and an input coil, and the flux transformer was inductively coupled with a Double Relaxation Oscillation SQUID(DROS). The flux-voltage modulation curve was induced by applying an AC magnetic field whose magnitude was far smaller than that of the DC magnetic field. A change in the flux-voltage modulation curve of the SQUID was observed while the DC magnetic field was increased, to qualitatively examine the current limiting characteristic of the Josephson junction array. As a result, it was found that the SQUID flux-voltage modulation curve disappeared at the critical current of the Josephson junction array, which indicates that the Josephson junction array properly works as a current limiter.