Engineering design and manufacturing of the modular coil system for the quasi-axisymmetric stellarator CFQS-T

• Engineering design of the modular coil system for the Quasi-axisymmetric Stellarator CFQS-T has been completed. • The validity of the modular coil system was confirmed by stress analysis using ANSYS/Mechanical and Maxwell. • Manufacturing method of the modular coils adopting vacuum pressure impregnation in two steps has been established. • All modular coils could be manufactured and assembled with less than a 2 mm dimension deviation which met an acceptance criterion. The Quasi-axisymmetric Stellarator CFQS has been constructed as an international joint project between the National Institute for Fusion Science in Japan and Southwest Jiaotong University in China. Its physical properties are as follows: toroidal periodic number m = 2 , aspect ratio A p = 4, maximum magnetic field strength B t = 1 T, and major radius of magnetic axis in vacuum R 0 = 1 m. The CFQS employs four different types of 16 modular coils to realize a quasi-axisymmetric magnetic field configuration. The CFQS plasma experiment is planned to have two stages. The first is a 0.09 T long-pulse operation with a simplified modular coil support structure referred to as “CFQS-T”. The second is a 1 T short pulse rated operation known as “CFQS” after reinforcing the modular coil system's support structure against a large electromagnetic force. This paper reports on the finalized engineering design of the modular coil system with simplified coil support structures for CFQS-T, including a validity evaluation result with finite element analysis method software ANSYS. Furthermore, the established manufacturing method of the modular coil system for CFQS-T is described. All modular coils for CFQS-T have been manufactured and its main body assembly, with modular coils and a vacuum vessel, has been completed. Currently the commissioning, including a coil energization test and magnetic field line mapping, is ongoing.