High temperature superconductors system

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. 

Metals and semiconductors are electronic conductors in which an electric current is carried by delocalized electrons. A metallic conductor is an electronic conductor in which the electrical conductivity decreases as the temperature is raised. A semiconductor is an electronic conductor in which the electrical conductivity increases as the temperature is raised. In most cases, a metallic conductor has a much higher electrical conductivity than a semiconductor, but it is the temperature dependence of the conductivity that distinguishes the two types of conductors. An insulator does not conduct electricity. A superconductor is a solid that has zero resistance to an electric current. Some metals become superconductors at very low temperatures, at about 20 K or less, and some compounds also show superconductivity (see Box 5.2). High-temperature superconductors have enormous technological potential because they offer the prospect of more efficient power transmission and the generation of high magnetic fields for use in transport systems (Fig. 3.42). 

Superconductivity has been known since 1911, and superconducting systems based on various metal alloys (e.g., NbTi and Nb3Sn) are currently used as magnets and in electronics. These materials exhibit superconductivity only at temperatures below 23 K and require cooling by liquid helium. The discovery of ceramics that exhibit superconductivity at temperatures up to 120 K, the so-called high-temperature superconductors, has sparked a tremendous amount of scientific activity and commercial interest around the world. 

Among the high-temperature superconductors one finds various cuprates (i.e., ternary oxides of copper and barium) having a layered structure of the perovskite type, as well as more complicated oxides on the basis of copper oxide which also include oxides of yttrium, calcium, strontium, bismuth, thallium, and/or other metals. Today, all these oxide systems are studied closely by a variety of specialists, including physicists, chemists, physical chemists, and theoreticians attempting to elucidate the essence of this phenomenon. Studies of electrochemical aspects contribute markedly to progress in HTSCs. 

Lead-based, high-temperature superconductors are being studied in several research projects. Their superior performance characteristics are expected to facilitate development of new hyper-fast computers, as well as more sensitive medical diagnostic equipment, more efficient energy delivery systems, and new forms of high-speed surface transportation. 

M.R. Jumaev Evolution of random pulses at nonlinear systems with fluctuating parameters -Dissertation for Doctor in Science in Theoretical Physics (2002) M.R. Jumaev NATO Advanced Research Workshop, Vortex dynamics and high temperature superconductors , Tashkent, Uzbekistan, 16-23 May 2002 (2002). M.R. Jumaev Evolution of random and regular pulses at nonlinear systems with constant and fluctuating parameters , Bukhara, Universitet (2004). 

High Temperature Superconductor (HTS) materials are wound within a cable system designed to also contain liquid nitrogen coolant. 

High-temperature superconductors. 285-288 Hinckley, C, C.t 6l3 Hoffman, R-. 387, 647 Homocyclic inorganic systems, 780-785... 

Calculations using the methods of non-relativistic quantum mechanics have now advanced to the point at which they can provide quantitative predictions of the structure and properties of atoms, their ions, molecules, and solids containing atoms from the first two rows of the Periodical Table. However, there is much evidence that relativistic effects grow in importance with the increase of atomic number, and the competition between relativistic and correlation effects dominates over the properties of materials from the first transition row onwards. This makes it obligatory to use methods based on relativistic quantum mechanics if one wishes to obtain even qualitatively realistic descriptions of the properties of systems containing heavy elements. Many of these dominate in materials being considered as new high-temperature superconductors. 

Another feature of the superconductivity effort has been that most has been devoted to detailed studies of existing materials rather than wide-ranging searches for new compositions. Substantially enhanced properties are necessary if high temperature superconductors are to have a major impact in the commercial sector. The assumption has been that detailed understanding will lead to improved superconductors. Usually, this has not occurred. The complexities of these underdetermined solid state systems restrict the ability to design improved structures. 

Because of the rapidly increasing availability of cryocoolers, numerous new applications have become possible many of these involve infrared imaging systems, spectroscopy, and high-temperature superconductors in the medical and communication fields. Many of these applications have required additional control of cryocooler-generated vibration and EMI susceptibility. 

D. B. Laubacher, Portable Nuclear Quadrupole Resonance Detection System for Detecting Presence of Explosives by Scanning Mail and Luggage, Uses High Temperature Superconductor Self Resonant Planar Transmit and Pick-Up Coil, US Patent Application No. US2004245988-A1 (2004). 

D. B. Laubacher and C. Wilker, Resonance Frequency Adjusting Circuit in Frequency Detection System, has Switch to Connect and Disconnect Reactance to Single Loop Coil Which Couples Circuit to High Temperature Superconductor Self-Resonant Transmit-and-Receive Coil, US Patent Application No. US2006012371-A1 (2005). 

Studies on other high-temperature superconductors Positron annihilation measurements across Tc, coupled with the calculations of PDD have been carried out in a variety of hole-doped superconductors that include YBa2Cu40g [48], Bi-Sr-Ca-Cu-0 [49], and Tl-Ba-Ca-Cu-0 [50, 51] systems. We will not labor with the details here, except to state that a variety of temperature dependencies are seen and these can be rationalized when the results are analysed in terms of positron density distribution and the electron-positron overlap function [39]. These calculations show that the positron s sensitivity to the superconducting transition arises primarily from the ability to probe the Cu-O network in the Cu-0 layer. The different temperature dependencies of lifetime, i.e., both the increase and decrease, can be understood in terms of a model of local electron transfer from the planar oxygen atom to the apical oxygen atom, after taking into account the correct positron density distribution within the unit cell of the cuprate superconductor. 

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