1. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
2. Consorzio RFX (CNR, ENEA, INFN, Universita di Padova, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova, Italy
3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
4. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
5. Department of Physics, Auburn University, Auburn, Alabama 36849, USA
6. Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA