Superconductor SQUIDs

Abstract An Eddy current method applying a High Temperature Superconductor ( HTS ) DC SQUID sensor operating at Uquid nitrogen temperature (77K) is presented. The method is developed for the detection of surface or surface near defects. We compare the performance of the SQUID system with the performance gained from a commercial Eddy current system, while using identical probes. The experimental data are obtained on defects in gas turbine blades. The advantage of planar conformable probes for the use with the SQUID is discussed. 

The crystals of SnNbsSe were obtained by dissolution of the A15 Nb3Sn superconductor in the dichalcogenide 2H-NbSe2 according to the method described in [1], The crystal sizes ranged from lxlx0.5 to 3x3x1 mm3. Preliminary susceptibility study of the compound by SQUID technique demonstrated temperature superconductivity transition at T 17.5 K [ 1 -3]. 

In this paper we explore the design of microwave-based structures that can enhance the interaction of electromagnetic fields with cold-atom ensembles, leading to novel sensing modalities based on the quantum-mechanical behavior of these systems In particular, we discuss electromagnetically-induced transparency in a single uncondensed cold-atom cloud, and a two-cloud version of a SQUID, where the clouds are EEC s and take the place of the weakly coupled superconductors. 

As we explore the interaction of cold-atom systems with microwave and terahertz radiation, we find that they have some unique properties as detectors. A comparison with superconductor-based detectors such as SQUlDs is instractive. Because of the third law of thermodynamics, i.e., a system in a single quantum state has zero entropy, the response of a SQUID is almost free of thermal noise. But an additional properly of SQUIDs is that they exhibit the phenomenon of coherence, i.e., wave interference, which leads to entirely new effects, e.g. the AC and DC Josephson effects. Cold atom clouds share this behavior, as we will discuss below. 

Superconductor Applications SQUIDs and Machines, ed. B. n Schwartz and S. Foner (Plenum Press, New York 1976). 

In this respect the superconducting quantum interference device (SQUID) is one of the most attractive developments. Many different designs have been fabricated and studied, and modem SQUIDs on the basis of YBa2Cu307 have reached field sensitivity and performance levels not far different from those known for devices produced with classical low temperature superconductors [13.3, 13.4]. 

Godfrey, Stephen. Carleton University Department of Physics. Superconductors BCS Theory, Josephson Junctions, SQUIDS, etc. Available from . 

Another current application of superconductors is superconducting quantum interference devices or SQUIDs. These devices can measure magnetic flux with an extremely high sensitivity, which is particularly useful for many purposes. The basis of such a high sensitivity is the... 

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