Browse Prior Art Database

High Magnetic Field Resolution RF Squid

IP.com Disclosure Number: IPCOM000100558D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Kirtley, JR: AUTHOR [+2]

Abstract

Disclosed is a structure for a single junction RF superconducting quantum interference device (SQUID) which contains a novel resonant shunting circuit across the junction.

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High Magnetic Field Resolution RF Squid

       Disclosed is a structure for a single junction RF
superconducting quantum interference device (SQUID) which contains a
novel resonant shunting circuit across the junction.

      There are two advantages of all RF SQUID structures. First, the
RF SQUID is coupled inductively at the input and output.  This
improves reliability.  Second, the RF SQUID has only one junction.
This improves manufacturability. However, thermal noise in the
Josephson junction of the RF SQUID and noise in the RF preamplifier
following the SQUID limit the resolution of an RF SQUID magnetometer
to less than a direct coupled double junction DC SQUID.

      In the disclosed structure, there is a resonant shunt (L,R,C)
in parallel with the Josephson junction (J) (see the figure).  The
resonant shunt suppresses thermal activation in the Josephson
junction (1).  This reduces the intrinsic noise of the RF SQUID.
This effect can be used in three ways.  First, the operating
temperature of the SQUID can be increased without loss of resolution.
 This is important for SQUIDs fabricated from high Tc materials.
Second, the critical current can be reduced and the loop inductance
increased (2).  This improves the coupling properties of the RF SQUID
and directly improves the magnetic field resolution of an uncoupled
device.  Finally, the drive frequency can be reduced to match the
noise in the preamplifier to the lower intrinsic noise in the RF
SQUID...