MBAR Shock Measurements in Copper-Doped Beryllium Driven by $\sim$50-EV Methane-Filled Halfraums

Copper-doped beryllium is being examined as a candidate ablator for National Ignition Facility capsules. 850-micron diameter, 30-60 micron thick, beryllium-copper wedges and steps were mounted on 800-micron diameter radiation exit holes of 1.6-mm diameter, 1.2-mm long, gold-wall, methane-filled halfraums. The halfraums were driven by three beams at the OMEGA laser (UR-LLE) to a steady radiation temperature Trad of $\sim $50-eV for up to 3.7 ns. $_{ }$An additional 10 beams, starting at 3.5 ns and ending $\sim $5.7 ns, are used to ramp the holhraums' Trad to $\sim $150 eV. VISAR measurements recorded shocks of approximately 1 Mbar. Measurements by a streaked optical pyrometer indicated that preheat was present for 30-40 micron thick samples within 1-ns of the start of the drive. We will present our data and analysis in comparison to as-shot simulations. *Work performed under U.S. DOE contract W-7405-ENG-36. LA-UR-05-5558