1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2. Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
3. CEA, DAM, DIF, F-91297 Arpajon, France.
4. Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA.
5. General Atomics, San Diego, CA 92186, USA.