Design of compensated solenoid based 1.0 T HTS magnet for extremity MRI

The low-temperature superconductor (LTS) based 1.0 T Extremity Magnetic Resonance Imaging (E-MRI), cooled by liquid helium are commercially available, however, their maintenance is expensive because of the global depletion of helium reserves. So, the helium usage in superconducting MRI scanners should be reduced and it is done by substituting it with liquid nitrogen/sub-cooled liquid nitrogen and the LTS are replaced by High-Temperature Superconductor (HTS). In this paper, a design of a 1.0 T E-MRI magnet with compensated solenoid approach is discussed. The solenoidal magnet consists of 4 mm wide second generation (2G) HTS tape which is wound in the form of double pancakes. The magnet design has been carried out with COMSOL multi-physics. An operating temperature of 65 K was selected for the improvement of the critical current of HTS tape for the generated magnetic field, with additional refrigeration requirement to produce subcooled LN2. A target field homogeneity of less than 50 ppm over a 100 mm diametric spherical volume was chosen for the design. The inner winding diameter of the coil is set as 200 mm and various coil configurations are compared by restricting its outer winding diameter and length to 500 mm and 300 mm respectively, for a fixed length of HTS tape. The design of compensated solenoid based HTS magnet involves the comparison of parameters such as peak axial and radial field, central flux density, field homogeneity and stray field distribution for a better configured E-MRI magnet. (author)