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Low-Noise Multi-Layer High Tc DC Squid

IP.com Disclosure Number: IPCOM000101074D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Kirtley, J: AUTHOR [+2]

Abstract

Disclosed is a novel structure for a double junction superconducting quantum interference device (DC SQUID). The body of the DC SQUID is fabricated from a film with relatively low current density. A separate groundplane is fabricated from a high quality film with small intrinsic flux noise. The groundplane is in close proximity to the body of the SQUID (see the figure). (Image Omitted)

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Low-Noise Multi-Layer High Tc DC Squid

       Disclosed is a novel structure for a double junction
superconducting quantum interference device (DC SQUID).  The body of
the DC SQUID is fabricated from a film with relatively low current
density.  A separate groundplane is fabricated from a high quality
film with small intrinsic flux noise.  The groundplane is in close
proximity to the body of the SQUID (see the figure).

                            (Image Omitted)

      The magnetic field resolution of an isolated DC SQUID scales
inversely with the loop inductance L to the 5/4 power.  However, the
SQUID characteristics are optimized for L = D0/ 2 I, where I is the
junction critical current.  A DC SQUID fabricated from a constriction
in a high Tc film has a critical current determined by the size of
the constriction and the current density of the film.  Thus, a low
current density film is necessary for a large inductance loop.
However, these films commonly have excess flux noise.  The flux noise
reduces the sensitivity of the SQUID (1).

      A multi-turn input coil tightly coupled to the SQUID loop
increases the sensitivity of the SQUID.  The inductance of this coil
scales with the loop inductance and the square of the number of turns
which can be efficiently coupled to the loop (2).  Thus, the SQUID
loop is frequently deformed into a broad washer (2).  However, this
washer would be an additional source of undesirable flux no...