Configuration characteristics of the Chinese First Quasi-axisymmetric Stellarator

The Chinese First Quasi-axisymmetric Stellarator (CFQS) will be the first operational quasi-axially symmetric stellarator in the world. The physical and engineering complexities led to the cancellation of two famous quasi-axisymmetric stellarators, CHS-qa and NCSX. Therefore, the major mission of the CFQS is to experimentally achieve the canonical quasi-axisymmetric configuration. The CFQS has been designed to possess a number of advanced features in fixed and free-boundary equilibria. It is a compact stellarator with an aspect ratio R/a similar to 4.0. The neoclassical diffusion coefficient is similar to that of tokamaks in the collisionless regime. The MHD equilibrium of the CFQS configuration is stable up to volume-averaged normalized pressure beta similar to 1.1%. A region of the second ballooning stability exists in this facility with a large region of plasma, becoming second stable for beta similar to 2.7% in free-boundary equilibria. The gap between the first and second stability boundaries is very narrow, which is greatly beneficial for the CFQS operation in the second stable regime with high beta plasma. A modular coil system with 16 coils is designed which robustly reproduces the standard quasi-axisymmetric magnetic field.

Automated summary

CFQS is the first operational quasi-axially symmetric stellarator in the world, aiming to achieve the canonical quasi-axisymmetric configuration experimentally. It has advanced features, compact design, and high pressure stability.