1. General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
2. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
3. Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550-9234, USA
4. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA