1. Institute of Power Engineering, Mory 8, 01-330 Warsaw, Poland
2. Department of Materials Science and Metallurgy, University of Cambridge, 27 Ch. Babbage Road, Cambridge CB3 0FS, UK
3. Department of Physics and Energy, Bernal Institute, University of Limerick, Castletroy, Ireland
4. Siemens MR Magnet Technology, Eynsham, OX29 4BP, UK