Design and cooling properties of high stable field REBCO superconducting magnet for MRI

Research and development for the practical application of a medical-use magnetic resonance imaging system (MRI) superconducting magnet that does not require liquid helium started as the New Energy and Industrial Technology Development Organization's (NEDO) supported project in fiscal 2016. Development of a liquid helium-free medical MRI superconducting magnet has been desired. Another purpose is to reduce the size and weight of high magnetic field magnets. By using the high temperature superconducting coil, it is possible to make the 3T magnet of the same shape, weight, leakage magnetic field as 1.5T magnet. In this project, we are developing a half size active shield-type 3T REBCO coil for MRI. This magnet has active shield coils with a maximum diameter of 1200 mm, and its room bore diameter is 480 mm. This magnet is one of the world's largest magnets using a REBCO wire with an accumulated energy of 1.6 MJ at the rated magnetic field. It generates a magnetic field of high homogeneity and stability necessary for imaging. In this paper, we report the half-size active shield-type 3T coil and its cooling system that can reduce the initial cooling time by thermal switches.