1. Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA
2. Princeton Plasma Physics Laboratory, 100 Stellarator Road, Princeton, New Jersey 08543, USA
3. The University of Texas at Austin, Austin, Texas 78712, USA
4. Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
5. Max Planck Institute for Plasma Physics, Boltzmannstr. 2, D-85748 Garching, Germany