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The University of Southampton
Rifi An Enterprise Consultancy Unit

Case Study: Thermal and electrical property measurements of aluminium alloys at cryogenic temperatures

Siemens MRI scanner
Siemens MRI scanner

Objective: To assess potential replacement materials for MRI scanners.

Situation

  • Siemens produce 30% of the world's MRI scanners; the thermal radiation shield is a critical component for the operation of the superconducting magnet.
  • The aluminium (A1) alloy used for the cryogenic thermal radiation shields is soon to be become obsolete.
  • Thermal and electrical properties of new A1 alloys (to define purity) have not been measured at cryogenic temperatures.
  • Bespoke cryogenic testing facilities and expertise was required.
  • What we did

  • Specialist machining of 500 micron thick specimens to minimise the heating and oxidation developed during cutting.
  • Microscopic measurement of the test specimens.
  • Used Physical Property Measurement System (PPMS) to obtain the thermal conductivity and electrical resistivity data in the cryogenic temperature range of 4.2K to 300K (cooled using liquid helium).
  • Analysed the cryogenic transition to evaluate the purity of seven different alloys.
  • Verified modelled results to evaluate the accuracy of the correlation used by Siemens to predict the purity of the A1 alloys.
  • Impact

  • Correlation can be confidently used to identify other potential A1 alloys more efficiently.
  • Siemens can be more selective with experimental testing, which is advantageous in view of the shortages of liquid helium available for experimental research.
  • Siemens has developed a database containing the cryogenic properties of new A1 alloys that is exclusive maintains a competitive advantage.
  • Outstanding customer satisfaction led to further work with Siemens to assess the effect of fabrication processing on the thermal and electrical properties of new A1 alloys.
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