1. Department of Mechanical and Aerospace Engineering, Princeton University Mechanical and Aerospace 1 , Engineering Room D-209 A/B—Business Center—Engineering Quad Olden Street Princeton, New Jersey 08544-5263, USA
2. Department of Astrophysical Sciences, Princeton University 2 , 4 Ivy Ln, Princeton, New Jersey 08544-5263, USA
3. Princeton Plasma Physics Laboratory, Princeton University 3 , 100 Stellarator Road, Princeton, New Jersey 08540, USA