Temperature Dependence of Optimal Shape and DC Current Transport Characteristics of 3 T Whole Body REBCO MRI Magnet

This paper reports the optimum design results of REBCO high-temperature superconducting magnets for 3 T-whole-body magnetic resonance imaging (MRI). The REBCO magnet consists of a main coil, compensation coil, and shield coil, and optimum design is carried out using an immunogenetic algorithm. A magnetic field uniformity of 20 ppm was observed in the uniform sphere inside the coil, and a 5-gauss region of 2.67 m in radial length and 4.50 m in axial length was realized. The local magnetic field vector distribution of the designed coil was also calculated for the designed magnet using electromagnetic field analysis, and the local voltage was obtained using the magnetic field/temperature dependence of the electric field vs. current density properties evaluated with the REBCO short sample. Then, the voltage vs. current characteristics of the magnet were evaluated by adding it over the entire coil length. Defining the current load factor (operating current/critical current) of the designed magnet using the above analysis results makes it possible to clarify the relationship between the operating current, optimized magnet shape, and required wire length for the operating temperature. In particular, we found that the required HTS tape length and transport current have a simple linear relationship in the operating temperature range below approximately 50 K.