Finite element analysis of the temperature distribution within a Conduction-Cooled, MgB₂-based MRI superconducting...

Area of Science:

• Applied Physics
• Materials Science
• Cryogenics Engineering

Background:

• Superconducting magnets in Magnetic Resonance Imaging (MRI) require minimal temperature gradients to maintain thermal stability and operating current margin.
• Maintaining uniform temperatures within MRI magnet windings is essential for reliable performance and longevity.

Purpose of the Study:

• To calculate the temperature distribution in an MRI segment coil using 3D finite element analysis (FEA), considering conductive and radiative heat transfer.
• To model the thermal property evolution during cool-down and analyze the impact of current lead design on temperature gradients and current margin.

Main Methods:

• Employed 3D FEA simulations in COMSOL Multiphysics, incorporating conductive heat transfer and radiative heating.
• Calculated heat capacity and thermal conductivity using a rule of mixtures and 2D FEA for composite cross-sections.
• Developed a time-dependent 3D coil model to simulate cool-down in a test cryostat, including heat leaks from current leads and cryostat surfaces.

Main Results:

• A maximum coil temperature difference (ΔT) of 5.1 K and a coil current margin (I_margin) of 12.75 A were predicted at steady state with the initial current lead design.
• Optimized current lead designs substantially reduced the steady-state ΔT within the coil.
• Analysis demonstrated the influence of different current lead designs on the coil's I_margin.

Conclusions:

• Optimized current lead designs are effective in minimizing temperature gradients within MRI superconducting coils.
• Reducing temperature gradients directly enhances the operating current margin, improving MRI magnet stability.
• FEA modeling provides a valuable tool for designing and optimizing cryogenic systems for MRI applications.