Using Permanent Magnets for Near Perfect Quasi-Symmetry in a Stellarator

Stellarators are very promising magnetic fusion energy confinement devices. Recent developments in stellarator theory, computational methods and the identification of the possibility of using permanent magnets for field shaping in stellarators have enabled a solution for confining energetic particles in stellarator geometry. This project uses tools developed for a recent ARPA-E project to verify that attractive magnet geometries exist.

Sufficient fast particle confinement has been identified as a key research need for stellarators in a recent paper from the National Stellarator Coordinating Committee. In a recent publication, Landreman and Paul demonstrated that a 2-period QA device could confine fast particles efficiently. In fact, good fast particle confinement was demonstrated over a range of magnetic equilibria. These configurations were identified using the newly developed SIMSOPT code. The key to achieving good confinement was the application of precise constraints on the degree of quasi-symmetry.

This work was done using an equilibrium solution constraint called ““fixed-boundary mode.” In this solution mode, external field sources are assumed to exist that provide the appropriate three- dimensional magnetic field. It is now crucial to demonstrate that these assumed highly-precise magnetic fields can be created using realistic field sources. The project will design such sources. This magnetic configuration could be used as the basis for a future experiment.

Dr. David Gates is the head of the Advanced Projects Department of the Princeton Plasma Physics Laboratory and the stellarator physics leader at the laboratory. He has a joint appointment as a senior research scholar at the Andlinger Center for Energy and the Environment. He leads collaborative efforts with the Wendelstein 7-X stellarator in Greifswald, Germany, and also on the Large Helical Device in Toki, Japan. He is currently the Principal Investigator of the project “Stellar Simplification using Permanent magnets.” Prior to taking the role as stellarator leader, he was the leader of the NSTX Advanced Scenarios and Control topical science group as well as head of the Magnetohydrodynamic (MHD) Stability group. He also was a Physics Operator on NSTX.

He completed his undergraduate studies in physics and mathematics at the University of Wisconsin-Madison and his graduate studies at Columbia University where he received his M.S., M. Phil. and Ph.D. in applied physics. He was a research associate at Culham Laboratory in Oxfordshire, England, from 1993–1997 where he worked on the COMPASS-D and START devices. He was a visiting professor at the National Institute for Fusion Science in Toki, Japan, in 2010 and 2011. He became a fellow of the American Physical Society in 2013.