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A study of the one-dimensional isentropic compression experiment (ICE), performed with High Explosive Pulsed Power (HEPP), has demonstrated that accurate, high stress, isentropic Equations of State (EOS) data may be obtained with this technique. The physics and accuracy of electromagnetic loading in the ICE technique are presented. It is shown that the HEPP-ICE load configuration is capable of producing magnetic stresses that are uniform to 1 part in 1000 over the central 87% of the sample faces, and that HEPP-ICE provides exact matching of the stresses between opposing samples. This magnetic uniformity, the exact matching, and the large sample sizes possible with HEPP-ICE, are necessary for the highest accuracy isentropic EOS data. The results for tungsten and copper demonstrate the inaccuracy of the technique, which may be as low as 0.2% in stress. [ABSTRACT FROM AUTHOR]

We have developed high explosive pulsed power (HEPP) methods to obtain accurate isentropic EOS data with the isentropic compression experiment (ICE). 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 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. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We are developing a prototype high explosive pulsed power (HEPP) system to obtain isentropic Equation of State (EOS) data with the Asay technique. Our prototype system comprises a flat-plate explosive driven magnetic flux compression generator (FCG), an explosively formed fuse (EFF) opening switch, and a series of explosively-actuated closing switches. The FCG is capable of producing ∼10 MA into suitable loads, and, at a length of 216 mm, the EFF will sustain voltages in excess of 200 kV. The load has an inductance of ∼3 to 10 nH, allowing up to ∼7 MA to be delivered in times of ∼0.5 μs. This prototype will produce isentropic compression profiles in excess of 2 Mbar in a material such as tungsten. We will obtain isentropic EOS data for copper at pressures up to ∼1.5 Mbar with the prototype system, immediately after this conference; eventually we plan to reach several tens of Mbar with larger, more advanced systems. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report on a pulsed power experiment performed at the Los Alamos National Laboratory Pegasus facility which was designed to measure material flow at metal interfaces driven to high relative velocities. Material motion at and near four flat Ta/Al(6061) interfaces was measured using flash radiographic techniques. A series of fine Pb wires (407 micron diameter) was implanted in the Al normal to the interfaces. The motion of these markers under shock loading provided a picture of material motion in the Al interfacial region. The surface roughness of the interfaces was varied between 32 and 125 micro-inches. We discuss the implications of these measurements for constitutive models of high speed friction and interfacial morphological change. [ABSTRACT FROM AUTHOR]

Experiments on the Pegasus pulsed power facility have investigated material failure and the growth of sinusoidal perturbations machined on the free inner surface of both A1 1100 and A1 6061-T6 samples undergoing shocked acceleration. The material behind the free surface exhibits massive microspall resulting in a volume of low-density material. Rapid pattern growth in the failed material and subsequent pattern growth on the surface, including jetting in some cases, were seen. Shock pressures were 15 GPa and 50 GPa. [ABSTRACT FROM AUTHOR]