1. Laboratory for Laser Energetics, 250 E. River Rd., Rochester, New York 14623, USA
2. Department of Physics and Astronomy, University of Rochester, Rochester, New York 14623, USA
3. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
4. Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada