Surface cooled, vacuum impregnated superconducting magnet systems : design, construction, applications

This thesis handles about the design and construction of three superconducting magnet systems for applications in the fields of medical imaging, plasma physics and nuclear physics. All three systems have vacuum-impregnated, intrinsically stable coils with cooling at the outer surfaces of the winding package with liquid Helium, and are all coupled in some way to closed cycle cooling systems. General theories are discussed only briefly, as the scope of this thesis is mainly to describe the techniques used in both the design and the construction of the different magnet systems. Special emphasis is given to the use of numerical methods for the calculation of thermal and mechanical properties of superconducting coil systems. In chapter 1, the general lay-out of the coil systems, their cryostats and the related cryogenic supply systems are given as they were published in the early days of these projects. The chapters 2 through 6 describe in more detail the design aspects of the systems like field calculations, aspects of thermal and mechanical stability, quench calculations,conductor design and t he related cryogenic systems. Also some physical properties of materials commonly used in superconducting magnet design are discussed. In the chapters 7 and 8 the final construction of the coils is described and results of the stress calculations are given for the three magnet systems. Different types of interfaces between the coils, cryostats and external systems are described in the chapters 9 and 10. We mention here current leads, transfer lines and control systems. In chapter 11 magnetic stray field problems, especially with respect to the installation of the Delft MR Imaging system are discussed and some possibilities are given to reduce these fields. Finally, the experimental results obtained with the Delft MR Imaging system are described and a few examples are given of images showing sagittal sections of the human head, successfully produced with this system.