Data on the high-pressure melting temperatures of metals is of great interest in several fields of physics including geophysics. Measuring melt curves is difficult but can be performed in static experiments (with laser-heated diamond-anvil cells for instance) or dynamically (i.e., using shock experiments). However, at the present time, both a Currently at Los Alamos National Laboratory 2 experimental and theoretical results for the melt curve of lead are at too much variance to be considered definitive. As a result, we decided to perform a series of shock experiments designed to provide a measurement of the melt curve of lead up to about 50 GPa in pressure. At the same time, we developed and fielded a new reflectivity diagnostic, using it to make measurements on tin. The results show that the melt curve of lead is somewhat higher than the one previously obtained with static compression and heating techniques.

Oral Session 7A: Fast Z-Pinches -111, Dense Plasma Focus; High Energy Density Using the Los Alamos high explosive pulsed power (HEPP) system, isentropic equation of state (EOS) data may be obtained for a wide range ofmatenals. Current pulses with risetimes of-SO0 ns and curHydrodynamics and Equation of State -rent densities exceeding 400 MNm, create continuous magnetic load-ing of samples at megabar pressures. We will summarize the technique and the problems that had to be overcome to perform the HEPP-ICE experiments at these pressures. We will then present our EOS results obtained with the conventional Lagrangian analysis and the Hayes' "Backwars' integration method', and compare the data with the published principal isentrope of OFHC copper.

We have developed high explosive pulsed power (HEPP) methods to obtain accurate isentropic EOS data with the isentropic compression experiment (ICE)[1] [2]. In the HEPP-ICE experiment, fast rising current pulses (with risetimes from 400 to 600 ns) at current densities of many MA/cm, create continuous magnetic compression of materials to Mbar pressures. The response of materials to this isentropic loading, as determined with VISAR measurements of free surfaces, provides the required isentropic EOS. Experiments on copper will be presented here. The data are analyzed using conventional Lagrangian and Backward [3] techniques. In the present arrangement four samples can be studied at one time, but accurate EOS data can only be obtained from opposing sample pairs, because it is only these pairs that share the same magnetic fields.