1. HSX Plasma Lab, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
2. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
3. Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany
4. Max-Planck/Princeton Research Center for Plasma Physics, 17491 Greifswald, Germany
5. Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA