Investigation of methods for screening inhomogeneous quasi-static magnetic fields over large surfaces using scalable structures involving high-temperature superconducting tapes

M. Nicolas Rotheudt will publicly defend his thesis entitled "Investigation of methods for screening inhomogeneous quasi-static magnetic fields over large surfaces using scalable structures involving high-temperature superconducting tapes".

Summary

The unrivalled electrical and magnetic properties of high-temperature superconductors pave the way for high-field, large-scale applications whose performance can greatly surpass that of conventional technologies. However, these engineering applications often generate significant low-frequency, inhomogeneous stray fields over wide surfaces. This thesis, therefore, explores how to design scalable high-temperature superconducting structures (‘magnetic screens’) which are able to attenuate these stray fields, i.e. confine the stray field lines on the device side to protect neighbouring equipment.

Single high-temperature superconducting components cannot be used satisfactorily as scalable magnetic screens: bulk samples are difficult to grow over wide surfaces and coated conductors alone have limited magnetic screening performance. One of the key achievements of this thesis is therefore to demonstrate the remarkable potential of hybrid screens combining a bulk sample with closed loops. This thesis provides a comprehensive study of these hybrid screens, both numerically using finite element modelling and experimentally using a bespoke 3-axis cryogenic Hall probe, in order to optimise them and explain physically their behaviour, the influence of physical and geometric parameters and the possible limitations. Such a study allows a screened surface area that largely overcome the state of the art to be measured (~9 times larger than that obtained with a bulk alone).

Another key achievement of this thesis is to investigate and demonstrate the potential of a scalable high-temperature superconducting screen combining bulk samples and coated conductors when subjected to the field produced, for the first time, by a practical large-scale engineering device. This device is a large superconducting coil which served as a demonstrator for a high-temperature superconducting wind turbine rotor.

The results of this thesis offer promising and exciting prospects regarding the potential of assemblies of superconductors as magnetic screens for next-generation engineering applications.

Practical information

Defence will take place on Thursday 9th  April at 9:00, to all at auditoire R7 - Institut Montefiore, Bât.B28, au Sart Tilman or via PhD Channel.