[1] Univ Wisconsin, Dept Phys, Madison, WI 53706 USA
[2] Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy
[3] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[4] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA
[5] Wheaton Coll, Wheaton, IL 60187 USA