Electricity: measuring and testing – Determining nonelectric properties by measuring electric... – Superconductors
Patent
1993-10-14
1996-04-09
Wieder, Kenneth A.
Electricity: measuring and testing
Determining nonelectric properties by measuring electric...
Superconductors
324636, 324708, 3332191, 333995, 505726, G01N 2700, G01R 2726
Patent
active
055064973
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a national phase of PCT/DE93/00105 filed 9 Feb. 1993 and based upon German national application P 42 04 369.7 filed 14 Feb. 1992 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a process for quality determination especially for determining the microwave surface resistance, of a single film formed on a substrate of a superconductive material, especially a high temperature superconductor, with the aid of an especially metallic cavity resonator with especially a circularly cylindrical interior. Further, the invention relates to a device for implementing such a process.
BACKGROUND OF THE INVENTION
Since the discovery of ceramic high temperature superconductors in 1986, the use of these materials has been demonstrated in, the field of passive microwave components as well as in the field of so-called Josephson components. Such passive microwave components from high temperature superconductive materials are of significance, among other things, for satellite communication. Practically all uses of this type make use of epitactic thin films of high temperature superconductive as have been produced in many laboratories throughout the world. One of the important criteria for the quality of such thin films is the microwave surface resistance. It constitutes a direct measure of the microwave losses in such components.
In the art there are basically two different processes described for the determination of the microwave surface resistance of a superconductive film.
It is known according to D. E. Oates, A. C. Anderson, and P. M. Mankiewich, J. Supercond. 3, 251, 1991, for example, to produce with the aid of photolithographic techniques planar resonators from the film to be investigated. Such measuring processes are expensive and are not suitable for rapid quality control of thin films.
An alternative kind of measuring process for determining the quality of such thin films is described in A. M. Portis, D. W. Cooke, and F. R. Gray, J. Supercond. 3, 297, 1991. In this measuring process, a wall of a metallic cavity resonator is formed by the thin film to be investigated. Such process requires no pretreatment of the probe and is thus suitable for quality control. This process, however, is suitable only for frequencies above 50 GHz. A process is known further from R. C. Taber, Rev. Sci. Instrum. 61, 2200, 1990, in which two superconductive films lying upon one another form a parallel-plate resonator. It is a disadvantage, however, that the average value of the surface resistance of two films is always measured. Aside from this, the total temperature curve of the surface resistance up to the break temperature cannot be determined.
OBJECT OF THE INVENTION
An object of the present invention is to provide an improved process and an apparatus for implementing the process which enables the quality control of individual thin films, especially of superconductive material with high sensitivity and without the drawbacks attributable to the state of the art.
SUMMARY OF THE INVENTION
This object is attained with a process in which the superconductive film is bonded of the cavity resonator as at least part of the wall of the resonator. The superconductive film is connected with a dielectric over a surface thereof. From an input antenna connected with the especially cylindrical wall, microwaves are coupled into the interior of the cavity resonator and a further output antenna, which can be disposed opposite the input antenna, is connected with the resonator to carry out signals from the interior of the resonator. The so outputted signals are further processed in a known manner, especially to determine the microwave surface resistance of the superconductive film. The quality determination of the superconductive film can, however, also reside in a processing of the outputted microwave signal to determine the penetration depths of the magnetic field. The superconductive film is preferably a high temperature superconductor.
By contrast wi
REFERENCES:
patent: 4968945 (1990-11-01), Woskov et al.
patent: 5105158 (1992-04-01), Fiedziusko et al.
patent: 5268646 (1993-12-01), Doss
patent: 5379110 (1995-01-01), Matsui et al.
O. Llopis, "Microwave Characterization Of High Tc Superconductors With A Dielectric Resonator", Journal of the Less-Common Metals, 1990, pp. 1248-1251.
Zhi-Yaian Shen et al., "High Tc Superconductor-Sapphire Microwave Resonator With Extremely High Q-Values Up to 90K", 1992 IEEE MTT-S Digest, pp. 193-196.
Dahne Ulrich
Klein Norbert
Tellmann Norbert
Do Diep
Dubno Herbert
Forschungszentrum Julich GmbH
Wieder Kenneth A.
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