5. Status of Physics Design of Ouasi-Axisymmetric Stellarators 5.2 Physics and Engineering Design of CHS-qa

A Iow aspect ratio helical device CHS-qa has been designed based on the quasi-axisymmetric configuration which is one of the new advanced stellarator concepts. As the basic necessary conditions for the new confinement experiment, ideal MHD stability has been examined for the Mercier, ballooning and kink stability criteria. A good quasi-axisymmetry was also realized keeping the good stability condition. As well as making efforts to reduce the neoclassical transport based on the quasi-axisymmetry, various considerations were made with respect to the experimental study of the improved confinement of helical systems from the viewpoint of the anomalous transport. In addition to the main modular coils, auxiliary coil systems are designed to give flexibility of the magnetic field configuration in CHS-qa, which are important to make good experimental study of the confinement physics.