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Development of a Superconducting Saddle Coil Magnet Mitsubishi Electric Corporation has developed and manufactured superconducting magnets to generate magnetic fields to pull up silicon single crystals as applied to Czochralski type equipment, MCZ. Mitsubishi Electric has succeeded in developing a superconducting magnet whose room temperature bore diameter is about 1.2 m. The magnet uses a pair of saddle type coils whose center magnetic flux density is about 0.5 T, with a maximum flux density of Bmax = 3.2T. See Figures 1 and 2 below. This magnet uses saddle type coils which consist of curved race-track coils paralleling the side of cylinder case, hence, it is much more compact than a conventional round-type two coil system, and can be replaced with a superconducting magnet generating a cusp magnetic field.
Figure 1. Schematic of superconducting curved saddle-type coils used for generating magnetic field to pull up silicon single crystals. Furthermore, there is a magnetic shield which reduces the magnetic flux leakage, and the electromagnetic interaction force with external iron. Although this magnet is cooled by pool-boiling liquid helium, the helium evaporation is reduced by using two cryogenic refrigerators. Even with the magnetic field being cycled on and off, the equipment generally operates for more than a month without re-supplying liquid helium. Chief Katsuyoshi of Toyota of Electric Power & Industrial System Works, Mitsubishi Electric, who participated in this magnet development said, "After this, we would like to aim at development of the same type larger diameter magnets and to meet the business world needs of the crystals for 300mm wafer together with superconducting magnets for cusp magnetic field applications."
Figure 2. The Mitsubishi Electric Corporation magnet system for single crystal silicon fabrication. The warm bore is about 1 m in diameter.
Superconducting Maglev Train Development Extended Five More Years The assessment committee for practical utilization of superconducting magnetically levitated train (Chairperson : Prof. Eisuke Masada at Science University of Tokyo) in the Ministry of Transportation recently met to evaluate the technical performance of the maglev train test runs since April 1997, and to discuss the technological development planning after the year 2000. The committee confirmed that the test runs at Yamanashi experimental line for the last three years has progressed according to the plan, and the technological development necessary for evaluating performance has advanced without troubles. Some of the notable maglev train achievements are: attaining 552 km/h, the highest velocity in the world in a manned run with a 5-coach train; a test run with two on-coming trains passing at a relative velocity of 1003 km/h (see Figure 3 below); and a drastic performance improvement in superconducting magnets. As a result of the assessment in performance necessary for a railway transport system, and the characteristics of this technology, the committee concluded the technological prospects of the practical future application as an ultra-fast mass transportation system look bright, but further development is required. Plans beyond the year 2000 should focus on solving the issues of long range durability, cost reduction, and improvement of the aerodynamic properties in the coach. To become a commercial technology, test runs should be performed on a nearly continuous basis for about five years. In response to this detailed assessment, Mr. Kasai, President of JR Tokai, said, "We are determined that our technological development over about 10 years results in the desired effects, and that they are significant." Mr. Fukushima, Administrative Director of the Railway Technical Research Institute (RTRI), said, "An independent evaluation that Japanese advances are of the highest level gives us great pleasure, and we will endeavor to do the technological development necessary for solving the next level of problems. " In order to solve the problems pointed out by the assessment committee, RTRI and JR Tokai established a five year plan for the future. The plan includes: (1) the verification of reliability and durability : using continuous long-term operation, carry out nonstop high speed test runs of vehicles, high frequency operational tests of power supply division switches etc., to verify reliability and durability; (2) towards reduction of construction and operation cost, develop new methods and make improvements in both equipment and instrumentation, e.g. electrical power converters and power supply systems, guide ways and ground coils for construction and electromagnetic-way equipment, superconducting magnets for vehicle equipment etc., and from year 2001 on, confirm equipment characteristics by test runs, and (3) improve the aerodynamic property of vehicles: use them in test runs from the year 2002, verify the reduction of aerial vibration, noise in vehicles, and vehicle vibration.
Figure 3. Two maglev trains passing in opposite directions at a relative speed of 1003 km/hr. |
