Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
1998-09-25
2001-05-01
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C505S846000, C257S034000, C327S527000
Reexamination Certificate
active
06225800
ABSTRACT:
The present invention relates to an arrangement for coupling an rf-SQUID magnetometer to a superconductive tank oscillating circuit and to a base plate.
Various proposals have been pursued heretofore for coupling rf-SQUID magnetometers to superconductive tank oscillating circuits.
Y. Zhang et al in “High-sensitivity microwave RF squid operating at 77 K”, SUPERCONDUCTOR SCIENCE AND TECHNOLOGY, vol. 7, No. 5, May 1, 1994, pages 269-272, XP000442664, teaches to employ a &lgr;-resonator or &lgr;/2-resonator, to which an rf-SQUID is coupled galvanically and at the same time functioning as a flow pivkup loop. Such a SQUID-magnetometer may have a tank frequency of 3 GHz.
The use of a &lgr;-resonator, however, poses problems it has a low quality of just a few 100. This represents a rather low quantity in view of qualities of a few 1000 reached already with &lgr;/2-resonators. Furthermore, the fact that galvanic coupling makes it necessary to take into account a parameter that is difficult to calculate, namely high-frequency current distribution, leads to considerable problems. High-frequency current distribution represents a quantity which is not easy to calculate or to control experimentally. Therefore, the SQUID-layout is difficult to optimize.
It is known from DE 44 36 448 to produce planar LC-oscillating circuits from thin YBaCuO-layers with high frequency and high quality. Such LC-oscillating circuits are operated in a flip-chip arrangement with the rf-SQUID in washer-SQUID structure. The parasitic capacities occurring in this connection between the LC-oscillating circuit and the rf-SQUID reduce the quality of the LC-oscillating circuit and make the current distribution in the combined LC-oscillating circuit structure/washer-SQUID structure complicated.
Therefore, the problem of the present invention is to create an arrangement which eliminates the aforementioned problems when an rf-SQUID magnetometer is coupled to a superconductive oscillating circuit.
The problem is solved in that the tank circuit and the rf-SQUID magnetometer are housed planar to each other on the same substrate, the tank circuit having a tank circuit coil and a laminar capacitative structure which enclose the rf-SQUID magnetometer.
The arrangement as defined by the invention relates to the possibility of advantageously and optimally coupling an rf-SQUID magnetometer to a tank circuit without the problems specified above. As opposed to the aforementioned flip-chip solution of the state of the art, the quality of the oscillating circuit is increased with the fully integrated arragement of the SQUID-magnetometer and the tank circuit even by factor 2 or 3, for example to a quality of Q=6000 at a resonance frequency of f
o
=580 MHz. One reason for such increase is that in the arrangement as defined by the invention, high-frequency radiation is reduced on account of the SQUID.
Furthermore, the fully integrated arrangement permits simple estimation of coupling “k” between the rf-SQUID and the tank circuit.
It is advantageous if the tank circuit consists of superconducting thin-layered material, thereby optimizing the characteristics of the arrangement of the invention.
It is particularly advantageous if the circuit coil of the tank circuit is designed as an inner loop enclosing the rf-SQUID magnetometer and having a slot. It is also especially advantageous if also the base plate is designed as an outer loop with slot and coplanar with the rf-SQUID magnetometer and the tank circuit because noise caused by the base plate can be suppressed in this way.
Furthermore, it is particularly advantageous that the orientation of the slots of the inner and outer loops relative to each other determines the resonance frequency. It is possible in this way to manufacture a multi-channel HTSL-SQUID system at favorable cost, for example for medical applications.
REFERENCES:
patent: 5326986 (1994-07-01), Miller, Jr.
patent: 5465049 (1995-11-01), Matsuura
patent: 40 03 524 A1 (1991-08-01), None
patent: 44 36 448 C1 (1996-02-01), None
patent: 44 33 331 A1 (1996-03-01), None
patent: 0 246 419 (1987-11-01), None
patent: 0 441 281 A2 (1991-08-01), None
Y. Zhang, et al. “High-sensitivity microwave RF SQUID operating at 77K”, Superconductor Science and Technology, No. 5, May 1994, pp. 269-272.
J.Z. Sun, et al., “Direct-Coupled High-TcThin Film Squids Using Step-Edge Weak-Link Junctions”, Applied Superconductivity, vol. 3, No. 7-10, pp. 425-441, 1995.
F. Ludwig, et al. “Multilayer Magnetometers Based on High-TcSquids”, Applied Superconductivity, vol. 3, No. 7-10, pp. 383-398, 1995.
Y. Zhang, et al. “HTS rf SQUIDS with Fully Integrated Planar Tank Circuits”, IEEE Transactions on Applied Superconductivity, vol. 7, No. 2, Jun. 1997, pp. 2870-2873.
T.D. Clark, et al, “Josephson-Effekt misst schwächste Magnetfelder”, Elektrotechnik, 65, H. 7, Apr. 1983, pp. 24-27 (no translation).
Banzet Marko
Schubert Jurgen
Soltner Helmut
Zander Willi
Zhang Yi
Collard & Roe PC
Forschungszentrum Julich GmbH
Snow Walter E.
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