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Title: The numerical solution of 'quench' in superconducting magnets
Author: Bottura, L.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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The scope of the thesis is the development and application of a model for the analysis of a quench in a large size, force-flow cooled superconducting magnet, i.e. the calculation of the thermal, hydraulic and electrical processes following the local transition of the superconducting material to the normal conducting state. The general problem is presented in Part A, with particular reference to the large size magnets designed for application in fusion experiments of the next generation. The presentation is as general as possible, so that the range of applicability is wide, and it indicates the intrinsically three-dimensional nature of the quench propagation in force-flow cooled magnets of the size considered here. The numerical methods which are necessary for the solution of the quench propagation are reviewed in Part B. A convective-diffusivemodel problem is used to analyze the performance of some of the most popular finite elements algorithms for steady state and transient solution. Amplification factors and phase lag of these algorithms are compared in order to make an optimal choice. A first approach to the solution of the quench propagation, based on a one dimensional model of the superconducting cable, is used in part C to build the basis of the general three dimensional analysis code and to test and validate the numerical against analytical solutions and experimental measurements. Finally, in part D, a fully three dimensional model for the quench propagation is proposed. The model is capable of dealing with arbitrary winding geometries, a wide spectrum of time variable boundary conditions for the flow of the coolant, time changing coil current and magnetic field distribution in the winding pack. At the moment this is the most complete analysis code for superconducting magnetic systems in normal and off-normal quenches (i.e. safety related transients). The 3-D model is tested against experimental results showing good agreement. The substantial work performed to simplify and extend the state equations and transport properties of the helium and of the solid materials used at cryogenic temperatures are reported in Appendices A and B respectively. Appendix C deals with the solution of the current in a general circuit configuration and with the calculation of the magnetic field in a coil of arbitrary shape. Finally, Appendix D presents an example of application to a large force-flow cooled magnet, the NET (Next European Torus) Model Coil, designed as a proof of principle for the NET magnet system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available