1. The Johns Hopkins University, Department of Physics and Astronomy, The Plasma Spectroscopy Group, Bloomberg Center, 3400 N. Charles Street, Baltimore, Maryland 21218
2. Associazione ENEA-EURATOM sulla Fusione, ENEA, Frascati, Italy
3. Princeton University Plasma Physics Laboratory, Princeton, New Jersey 08543
4. Columbia University, New York, New York 10027