It is widely recognized among stellarator researchers that the minimum distance between the plasma boundary and the middle of the coil (
min) is of great importance for stellarators as it impacts the machine parameters considerably. Techniques for minimizing the radial build have made impressive progress during the first year of the ARIES-CS study. A novel approach has been developed for ARIES-CS where the blanket at the critical area surrounding min has been replaced by a highly efficient WC-based shield. As a result, an appreciable 20-90 cm savings in the radial build has been achieved, reducing the major radius by more than 20%, which is significant. The economic benefit of this approach is yet to be determined and the added engineering problems and complexity will be addressed during the remaining period of the study. This paper covers the details of the radial build optimization process that contributed to the compactness of ARIES-CS. Compared with previous designs, the major radius of ARIES-CS has more than halved, dropping from 24 m to less than 10 m, making a step forward toward the feasibility of a compact stellarator power plant.
