Introduction to High-Temperature Superconductivity (Selected Topics in Superconductivity)
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High temperature superconductivity (HTSC) hast he potential todramatically impact many commercial markets, including the electric power industry. Since 1987, the Electric Power Research Institute (EPRI) has supported aprogram to develop HTSC applications fort he power industry. The purpose ofEPRI is to manage technical research and development programs to improve power production, distribution, and use. The institute is supported by the voluntary contributions ofs ome7 00 electric utilities and has over 600 utility technical experts as advisors. One objectiveo f EPRI's HTSC program is to ed ucate utility engineers andexecutives on the technical issues related to HTSC materials and the supporting technologies needed for their application. To accomplish this, Argonne National Laboratory was commissioned to preparea series of monthly re ports that would explain th e significanceo f recent advances in HTSC. Acomponent o f each report was a tutorial on some aspect of the HTSC field. Topics ranged from the various ways that thin films are deposited tot he mechanisms used to operatem ajor cryogenic systems. The tutorials became very popularw ithin the utility industry. Surprisingly, the reports also became popular with scientists at universities, corporate labo ratories, and thenational laboratories. A lthough these researchers are quite experienced in one aspect of the technology, they are nots ostron g inothers. Itw ast he diversity and thoroughness ofthe tutorials that made them so valuable.
rolling, or swaging follows, leaving a final shape well below 1 mm in diameter but very long. To restore the ceramic core to the superconducting state, it is necessary to heat treat it further, at perhaps 800–900°C. Finally, the wire must be annealed in oxygen very slowly (typically 100 hours) in order to allow oxygen atoms to slowly recover their proper positions in the crystal lattice. Without this step, only a small percentage of the material would be superconducting, and the wire would not
happens. A flux line can be stopped in its sideways motion by grain boundaries, impurities, or many other kinds of impediments. The flux line is said to be pinned. A nearby flux line, about one penetration length away, feels the influence of the pinned line. Thus, when another moving flux line bumps into that one, it too stops moving, and soon the traffic jam of flux lines form a lattice, none of which can move unless they all move at once. The word frozen is used to denote that the lattice of
accepted medical practice.15 97 92 CHAPTER 5 A great deal of benefit can be obtained without knowing the details of exactly what is going on in the brain. The value of good MEG measurements is truly stunning: Figure 5.10 is an MEG image of a patient’s brain in which a tumor lies close to important blood vessels and close to the sensory cortical region that processes sensations of the hand and face. When someone is about to have a brain tumor removed, MEG scanning beforehand can show the
differs only very slightly in length from a. In the latter case, as the unit cell is repeated again and again during crystal growth, it is quite easy for the a and b axes to become reversed. There is then a slight change in the direction of the orientation. Not enough to be considered an entirely new grain, this phenomenon is called twinning. STRUCTURE 139 Every distinct type of unit cell has its own name. If all the lattice dimensions are equal (i.e., a = b = c) and all the corner angles
single crystals. Any liquid having the stoichiometric ratios for 1-2-3 lies in the primary phase field for 2-1-1, the nonsuperconducting green phase. Upon cooling, 2-1-1 is what first comes out. The primary phase field for 2-1-1 is much bigger than for 1-2-3. Figure 9.18 is another top-down view like Figure 9.16, but with the primary phase fields for 2-1-1 and 1 -2-3 overlaid on it. Evidently, to make 1-2-3 from the liquid state, it is necessary to start out very copper-rich. Crystals of 1-2-3,