1. Lawrence Livermore National Laboratory, Livermore, California 94551, USA
2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
3. Laboratoire pour L'Utilisation des Lasers Intenses, Ecole Polytechnique, 91128 Palaiseau Cedex, France
4. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14620, USA