The static background field in commercial magnetic resonance imaging (MRI) body scanners is generated by superconducting magnets operating in persistent-mode without a power supply. The magnets typically contain more than10 joints between separate lengths of NbTi multifilamentary superconducting wire, each of which must have a resistance <10-13 to enable persistent mode operation. In order to charge the magnet in the first instance, a special joint is needed to form a superconducting switch. On installation of the magnet, the switch is opened to allow current to be driven into the magnet from a power supply and then closed to form a continuous superconducting circuit so the power supply can be removed. Current technology exploits the superconducting/normal transition to drive the switch joint normal during the charging process by heating.
This project, funded by Siemens Heathineers who manufacture ~1/3 of MRI magnets worldwide, will develop a new switch system capable of controlling a high current superconducting circuit through physically demountable superconducting contacts. The project will be co-supervised by A Thomas at Siemens. It will involve investigating and selecting suitable contact materials, and explore the processing techniques for creating suitable interfaces or intermediary layers between the main current carrying superconducting materials. The overall aim is to developing an engineering solution to the design of the contact surfaces. It is anticipated that a wide range of superconducting materials and methods of application will be investigated to determine viable and optimal combinations. The project is intended to take the concept to Technology Readiness Level 4 – offline concept validation.
The student will use the extensive facilities for joint fabrication, microstructural characterisation and testing in the Oxford Centre for Applied Superconductivity (CfAS) to develop materials, and state-of-the art facilities at the nearby Siemens manufacturing facility for measuring the high current persistent behaviour of superconducting joint to evaluate the engineering performance of contacts, including their tolerance to background magnetic fields. This project will give a student interested in the field of applied superconductivity the opportunity to become expert in the fundamental properties of practical superconductors and to apply this understanding to develop an engineering solution to a real industrial problem.
Candidates will be considered in the November 2020 admissions field which has an application deadline of 13 November 2020 and, if the studentship is unfilled, in subsequent admissions fields, the next of which has an application deadline of 22 January 2021.
Any questions concerning the project can be addressed to Professor Chris Grovenor ([Email Address Removed]) or Professor Susie Speller ([Email Address Removed]). General enquiries on how to apply can be made by e mail to [Email Address Removed]. You must complete the standard Oxford University Application for Graduate Studies. Further information and an electronic copy of the application form can be found at http://www.ox.ac.uk/admissions/postgraduate_courses/apply/index.html.
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