[1] Gen Atom Co, San Diego, CA 92186 USA
[2] Max Planck Inst Plasma Phys, Garching, Germany
[3] Univ Calif San Diego, San Diego, CA 92103 USA
[4] MIT, Plasma Sci & Fus Ctr, 77 Massachusetts Ave, Cambridge, MA 02139 USA
[5] Oak Ridge Natl Lab, Oak Ridge, TN USA