摘要 :
These sessions had been designated as “interactive,” with the hope of defining some of the problem areas that are frequently encountered during magnet development projects. Whilst the list above represents only the broad outline...
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These sessions had been designated as “interactive,” with the hope of defining some of the problem areas that are frequently encountered during magnet development projects. Whilst the list above represents only the broad outline of the two hours of discussion that produced it, there are clearly a number of recurring themes. Using this list as a starting point, a “Materials Workshop” would now seem to be appropriate, that would attempt to answer some of the points raised and to provide the `focus' groups that could consider the problem areas in more detail
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Superconductivity was discovered in 1911 by Kamerlingh Onnes and Holst in mercury at the temperature of liquid helium (4.2 K). It took almost 50 years until in 1957 a microscopic theory of superconductivity, the so-called BCS theo...
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Superconductivity was discovered in 1911 by Kamerlingh Onnes and Holst in mercury at the temperature of liquid helium (4.2 K). It took almost 50 years until in 1957 a microscopic theory of superconductivity, the so-called BCS theory, was developed. Since the discovery a number of superconducting materials were found with transition temperatures up to 23 K. A breakthrough in the field happened in 1986 when Bednorz and Müller discovered a new class of superconductors, the so-called cuprate high-temperature superconductors with transition temperatures as high as 135 K. This surprising discovery initiated new efforts with respect to fundamental physics, material science, and technological applications. In this brief review the basic physics of the conventional low-temperature superconductors as well as of the high-temperature superconductors are presented with a brief introduction to applications exemplified from high-power to low-power electronic devices. Finally, a short outlook and future challenges are presented, finished with possible imaginations for applications of room-temperature superconductivity.
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A high-T/sub c/ superconductive fluxgate magnetic sensor utilizing sintered YBa/sub 2/Cu/sub 3/O/sub 7-x/ core is constructed and applied to detect a flaw in an aluminum plate. The magnetic sensor successfully works in an unshield...
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A high-T/sub c/ superconductive fluxgate magnetic sensor utilizing sintered YBa/sub 2/Cu/sub 3/O/sub 7-x/ core is constructed and applied to detect a flaw in an aluminum plate. The magnetic sensor successfully works in an unshielded environment. An electric current was supplied to an aluminum plate directly. A slit (0.2 mm width, 30 mm length), which is considered as a flaw, on an aluminum plate is successfully detected with this sensor, even though the slit is covered with another aluminum plate. The sensor can detect the flaw with its direction perpendicular to the electric current in the sample. It's supposed that the sensor can determine the length of the flaw larger than the diameter of the detection coil. These results suggest that the sensor has a potential for nondestructive evaluation of non-magnetic metals such as aluminum alloys, and also for their multi-layered structures.
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Superconductivity synchronous motors compared with conventional motors can reduce the motor size and enhance the motor efficiency for low-speed and high torque applications under the space constraints for propulsion system. Especi...
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Superconductivity synchronous motors compared with conventional motors can reduce the motor size and enhance the motor efficiency for low-speed and high torque applications under the space constraints for propulsion system. Especially, homopolar superconductivity synchronous motors (HSSMs) need less superconductor and lower magnetic flux density in superconductor field coil than air-cored superconductivity synchronous motors (ASSMs). In addition, mechanical structure is more simplified and stability is increased because the superconductor field coil of HSSMs is not rotated in operation. In this paper, we present the outline of HSSMs including structure, characteristics and operational principles with the conceptual design of HSSM.
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A 24-T superconducting toroidal field magnet concept for a commercial fusion power reactor is discussed, and a magnet development path is outlined. Superconducting and structural materials options are discussed within the framewor...
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A 24-T superconducting toroidal field magnet concept for a commercial fusion power reactor is discussed, and a magnet development path is outlined. Superconducting and structural materials options are discussed within the framework of a 20-yr development time. Nb/sub 3/Sn may be capable of operating at up to 18-20 T. For B<20 T, Nb/sub 3/Al, Nb/sub 3/(Al,Ge) or ceramic high-T/sub c/ superconductors are required. Enhanced strength and stiffness and reduced conductor bending stress are obtained with carbon fiber reinforced steel (Incoloy 908) as the primary structural material. Composite behavior is analyzed using a two-dimensional orthotropic failure criterion. The size of the magnet is minimized subject to electromagnetic, mechanical, and practical constraints.
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Some background information on superconducting ceramics is given, and the history of yttrium barium copper oxide (YBCO) is discussed. The crystal structure of superconducting YBCO is described. The production and extraction method...
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Some background information on superconducting ceramics is given, and the history of yttrium barium copper oxide (YBCO) is discussed. The crystal structure of superconducting YBCO is described. The production and extraction methods of bulk samples of YBCO are detailed. Different theories of superconductivity in YBCO are addressed, and applications of YBCO superconductors are discussed.
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A critical component of the SSC (Superconducting Super Collider) dipole magnets is superconducting cable. The uniformity and reliability requirements for the dipoles place stringent demands on the cable. These needs have been defi...
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A critical component of the SSC (Superconducting Super Collider) dipole magnets is superconducting cable. The uniformity and reliability requirements for the dipoles place stringent demands on the cable. These needs have been defined as various contract requirements in the material specifications for NbTi alloy, superconducting wire, and cable. A supplier qualification program is being started by the SSC Laboratory (SSCL) with industry to establish reliable sources of superconductor cable. To monitor conductor performance, a computer database is being developed. The database focuses on the understanding and control of variation in the manufacture of wire and cable. A statistical and graphical summary of current data for key performance variables is presented in light of the specification requirement for uniformity. Superconductor material characteristics addressed include wire critical current, copper-to-non-copper ratio, wire diameter, wire piece-length, and cable dimensional control.
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Superconducting magnetic energy storage (SMES) systems are analyzed with respect to the potential impact of advancing materials technology. The effects of increased superconductor current density, magnet operating temperature and ...
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Superconducting magnetic energy storage (SMES) systems are analyzed with respect to the potential impact of advancing materials technology. The effects of increased superconductor current density, magnet operating temperature and structural material strength are evaluated. For relatively low-field (>17-T) coils, NbTi and Nb/sub 3/Sn are used. For higher magnet fields and operating temperatures, the ceramic oxide BiSrCaCuO is anticipated in the near term (within 5-10 years). Advanced structural materials are also considered. These include cryogenic steels, maraging steels, and titanium alloys. Of these, Incoloy 908 (a cryogenic steel) is found to be the most suitable material for a small SMES system. The impact of fiber-reinforced steel composites is also evaluated. If all of the advances discussed become available (increased current density, operating temperature and allowed stress), the net conductor, structure and cryogenic cost of 10-MWh SMES systems may be reduced by over 45% relative to presently available technology.
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The Grenoble Hybrid Magnet produces fields above 30 T in a room temperature bore as big as 50 mm in diameter. It uses superfluid technology and a polyhelix insert. The authors give the main characteristics of this magnet and descr...
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The Grenoble Hybrid Magnet produces fields above 30 T in a room temperature bore as big as 50 mm in diameter. It uses superfluid technology and a polyhelix insert. The authors give the main characteristics of this magnet and describe the operating conditions under which the system is run for scientific use. Only a few modifications have had to be introduced since the magnet became operational in 1986. The resistive part has been subject to two technical improvements to increase water flow and reduce operating temperature, and a fast data acquisition system was added to analyze quench behavior. The superconducting magnet quenched twice and showed a behavior exactly as calculated. No deterioration has been observed in spite of the high discharge voltage of 2.5 kV. The cryogenic system has proven to be quite reliable except for a few problems with the liquefying system and a clogged filter in front of the 1.8/4.2-K heat exchanger.
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