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dc SQUID – SQIF Sensor with High Transfer Function Based on Sub-micrometer Cross-type Josephson Tunnel Junctions
T. Schönau, M. Schmelz, V. Zakosarenko, R. Stolz, S. Anders, L. Fritzsch, H.-G. Meyer
Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745 Jena, Germany
Abstract - The sensor, called herein GHS, is based on a dc SQUID connected to a SQIF that amplifies the voltage from the first stage SQUID. The SQIF consists of an array of SQUIDs with various inductances, facilitating a unique global minimum in the flux-voltage-characteristic and ensures a stable working point, a high voltage swing and a large transfer function of the GHS. Sub-micrometer cross-type Josephson junctions are used for the GHS. Due to their low capacitance, the sensors exhibit low magnetic flux noise and a high voltage swing. The voltage swing of the SQIF can exceed 3 mV which enables us to use of a high-bandwidth directly coupled SQUID electronics. Part of the current of the SQIF can be optionally fed back to the input coil of the first stage SQUID, so that an on-chip linearization is realised. The used sub-micron cross-type junctions withstand high background fields during cool-down of up to 6.5 mT. The high voltage swing as well as the optional on-chip linearization make this setup well suited for applications in strong magnetic fields where high slew rates are required, like, e.g., the transient electromagnetic method (TEM) used in geomagnetic exploration.
Presented at the KRYO 2011 Workshop, Autrans, France, October 2-4, 2011, Reference No. STP278, Category 4.
Paper based on this presentation is published in Supercond. Sci. Technol. 25 015005 (2012)