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Improved Parallel Wired Superconducting Thin Film Transducer

IP.com Disclosure Number: IPCOM000119695D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Related People

Tesche, CD: AUTHOR

Abstract

A technique is described whereby an improved parallel wired superconducting thin film transducer reduces the magnetic field at the Niobium membrane, thereby improving the performance of the transducer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Improved Parallel Wired Superconducting Thin Film Transducer

      A technique is described whereby an improved parallel
wired superconducting thin film transducer reduces the magnetic field
at the Niobium membrane, thereby improving the performance of the
transducer.

      Generally, the most sensitive superconducting motion
transducers are used in bar-type gravitational radiation detectors.
The transducer consists of a superconducting membrane which is used
to shield the inductance of one or more superconducting loops Lp, as
shown in Fig. 1.  A bias current I is loaded into the pick-up loops
where small displacement changes the inductance of Lp1 and Lp2.  This
produces an imbalance in the input circuit sending a signal current J
through coupling coil Lc, which is then detected by a superconducting
device (SQUID).  The superconducting transducer of 1 is usually
fabricated from a bulk Niobium membrane and bulk Nb wire pick-up
coils Lp.  Electrical losses in this structure limit the Q to
approximately 104, which is dramatically less than the mechanical Q
of 109 for silicon at 4_, and the mechanical Q of a bar detector of
7 x 106 .  This low electrical Q is believed to be related to losses
in the membrane when large magnetic fields generated by the bias
current I are applied.  The thin film, as shown in Fig. 2, was
suggested in 2.  The bias current I is increased until the field at
the ground plane is near the critical field.  The signal is:
                   delta I   -1  I
                   ------- = -- --
                   delta X    2  X

      The following design incorporates the transducer improvements:
PARALLEL-WIRED TRANSDUCER

      Fig. 3 illustrates the use of Ns stripline inductances in
parallel. Pickup coils Lp are wound in opposition so as to provide a
self-shielded structure.  The self-shielding is produced by virtue of
the geometry (gradiometer), independent of the values of I1 and I2.
RESOLUTION
      For a matched transformer Li=Lp/2, the signal is
            delta J  ...