Composite bulk superconducting magnets for high field applications

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The RE-Ba-Cu-O (where RE= rare earth element such as Y, Nd, Sm, Gd, etc.) family of bulk, melt processed high temperature superconductors [(RE)BCO] is the subject of extensive world-wide research due primarily to their potential to trap large magnetic fields. This has been demonstrated spectacularly by the Cambridge Bulk Superconductivity Group, which recently set a new world record trapped field of 17.6 T at 26 K using these materials, breaking the previous world record that had stood for more than 10 years. The Cambridge Group has been at the forefront of research in this area for the past 20 years and, in addition to funding from EPSRC and other government sources, has attracted substantial and sustained industry funding. Bulk (RE)BCO superconductors have reached an important and critical stage in their research and development. Their spectacular field generating properties have high potential for a range of sustainable engineering applications, including flywheel energy storage, motors and generators, magnetic separators, bio-medical applications and magnetic levitation devices. This proposal is for a unique and timely combination of fundamental materials research and the development of practical assemblies to generate practical magnetic fields using bulk superconductors that can be used routinely and commercially in engineering devices for the first time. The main objective of the project will be to shape the magnetic field at low temperatures (50 K and 30 K), where critical current, and hence field generating capability, is significantly higher than at 77 K. Materials to improve the mechanical strength and the thermal conductivity for incorporation in the sample and assembly structures will be developed to obtain optimum performance in high field for samples and assemblies magnetised specifically by pulse magnetisation. It is becoming increasingly likely that rapidly developing cryo-cooler technology will enable practical applications at temperatures below 77 K, and this will drive the development of improved materials and new structures. The single grain, (RE)BCO bulk superconductors developed with improved mechanical strength and thermal conductivity will be incorporated into assemblies of different composite shapes of different (RE)BCO materials to enable the control of magnetic field strength and distribution. The properties and performance of these assemblies will be compared with larger sized, individual samples of comparable surface areas at 77 K where the requirement for mechanical strength is relatively modest. Capability developed during our current EPSRC grant on multi-seeding will further enable the fabrication of multi-seeded, quasi-single grains, whose properties will be compared with an assembly of smaller, closely packed samples of similar sizes. The trapped field and levitation force of assemblies of different (RE)BCO superconductors arranged in different orders will be measured at 77 K and compared with the properties of conventional, single grains of the same size.The project, which will continue to support outreach in UK school, colleges and universities, benefits from strong financial support of major international industrial collaborators, including the Boeing Company, Siemens and Bio-med (UK).