Engineering design of the Chinese First Quasi-Axisymmetric Stellarator (CFQS)

The Chinese First Quasi-Axisymmetric Stellarator (CFQS) is being constructed as an international joint project between the National Institute for Fusion Science in Japan and Southwest Jiaotong University in China. It is being designed as a low-aspect-ratio quasi-axisymmetric stellarator with a modular coil system in a CHS-qa configuration. The physics design is almost finished, and we are now proceeding with the engineering design. Its physical properties are as follows: toroidal periodic number m = 2, aspect ratio A_p = 4, magnetic field strength B_t = 1 T, major radius R₀ = 1 m, and typical rotational transform iota-bar = 0.4 in the all-radial region. We are currently evaluating the design's technical feasibility and manufacturability using a 3D CAD system, together with structural and electromagnetic analysis software. This paper reports on the CFQS's feasibility from an engineering design viewpoint. We are currently targeting 16 normal conducting modular coils, divided into four types, and a total current of 5 MAT. Each coil has a rectangular cross section of 132×69 mm², and is composed of 72 hollow copper conductors with water-cooling holes. These conductors carry currents of 4.3 kA, with a current density of 74 A/mm². (author)