A coupled DC SQUID with low 1/f noise

Heikki Seppä, Mikko Kiviranta, Alexandre Satrapinski, Leif Grönberg, Jorma Salmi, Ilkka Suni

    Research output: Contribution to journalArticleScientificpeer-review

    27 Citations (Scopus)


    A low-noise coupled DC superconducting quantum interference device (SQUID) especially optimized for low frequency is discussed. Using large Josephson junctions and a low loop inductance the contribution of the critical current fluctuation to 1/f noise can be minimized. To minimize the inductance the Josephson junctions are placed in the center of the washer close to the SQUID loop. A scaled-up copper model of the SQUID and the signal coil is used to analyze the impedance of the SQUID loop affected by the signal coil. An equivalent circuit model describing the effective inductance of the SQUID loop as a function of the frequency is used to design appropriate damping of the resonances. The DC SQUID characteristics are smooth and the noise performance of the SQUID does not markedly suffer from resonances. The contribution of the 1/f noise at 1 Hz is found to be about 5*10-7 φ0 √Hz.
    Original languageEnglish
    Pages (from-to)1816 - 1819
    Number of pages4
    JournalIEEE Transactions on Applied Superconductivity
    Issue number1
    Publication statusPublished - 1993
    MoE publication typeA1 Journal article-refereed


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