1. Lawrence Livermore National Laboratory, Livermore, California 94551, USA
2. Washington State University, Pullman, Washington 99164, USA
3. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA
4. University of California Berkeley, Berkeley, California 94720, USA
5. Stanford Linear Accelerator Center, Menlo Park, California 94305, USA
6. Institute of Physics, University of Rostock, 18059 Rostock, Germany
7. Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany