Improving confinement in the HSX Stellarator with Permanent Magnets

The field of the stellarator experiment has a “ripple” effect due to discrete coils. The reduction of the ripple is essential, as particle confinement is highly sensitive to small errors in the magnetic field. This project aims to correct toroidal ripple in the confining magnetic field by utilizing permanent magnets to reduce or remove the ripple. The HSX Stellarator is used as a test case for this concept. Several magnet solutions were explored by generating different arrangements, optimizing the magnets’ dipole moments, and assessing the reduction in field error value. It was determined that magnets placed on the inboard side of the stellarator yielded a lower field error. Two magnet arrangements were compared, and it was found that the arrangement with magnets placed on the inboard side resulted in a five times better field error than the one with no present magnets on the inboard side. These results demonstrate the potential for using permanent magnets to reduce field error.

This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.