Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session D1: Experimental Developments I: Pulsed-Power Experiments |
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Chair: Todd Haines, Los Alamos National Laboratory, Marcus Knudson, Sandia National Laboratories Room: Grand E |
Monday, June 15, 2015 2:00PM - 2:30PM |
D1.00001: Obtaining off-Hugoniot equation of state data on solid metals at extreme pressures via pulsed-power driven cylindrical liner implosions Invited Speaker: Raymond Lemke The focus of this talk is on magnetically driven, liner implosion experiments on the Z machine (Z) in which a solid, metal tube is shocklessly compressed to multi-megabar pressure. The goal of the experiments is to collect velocimetry data that can be used in conjunction with a new optimization based analysis technique to infer the principal isentrope of the tube material over a range of pressures. For the past decade, shock impact and ramp loading experiments on Z have used planar platforms exclusively. While producing state-of-the-art results for material science, it is difficult to produce drive pressures greater than 6 Mbar in the divergent planar geometry. In contrast, a cylindrical liner implosion is convergent; magnetic drive pressures approaching 50 Mbar are possible with the available current on Z ($\sim$ 20 MA). In our cylindrical experiments, the liner comprises an inner tube composed of the sample material (e.g., Ta) of unknown equation of state, and an outer tube composed of aluminum (Al) that serves as the current carrying cathode. Internal to the sample are fielded multiple PDV (Photonic Doppler Velocimetry) probes that measure velocity of the inner free surface of the imploding sample. External to the composite liner, at much larger radius, is an Al tube that is the return current anode. VISAR (velocity interferometry system for any reflector) probes measure free surface velocity of the exploding anode. Using the latter, MHD and optimization codes are employed to solve an inverse problem that yields the current driving the liner implosion. Then, the drive current, PDV velocity, MHD and optimization codes, are used to solve another inverse problem that yields pressure vs. density on approximately the principal isentrope of the sample material. Results for Ta, Re, and Cu compressed to $\sim$ 10 Mbar are presented. [Preview Abstract] |
Monday, June 15, 2015 2:30PM - 2:45PM |
D1.00002: Pulsed-Power Driven Liner-On-Target Hydrodynamics Experiments Diagnosed with Proton Radiography using PHELIX D.M. Oro, C.L. Rousculp, W.A. Reass, J.R. Griego, P.J. Turchi, R.E. Reinovsky, A. Saunders, F.G. Mariam, C. Morris The Precision High Energy-density Liner Implosion eXperiment, PHELIX, is a pulsed-power driver capable of delivering multi-mega-ampere currents to cylindrical loads. The pulsed-power system utilizes a high-efficiency transformer to couple a small capacitor bank ($\sim$400 kJ) to a $\sim$5 cm diameter cylindrical Al liner. A peak current of $\sim$4 MA causes the liner to implode in 20 -- 30 $\mu$s and attain speeds of $>$1 km/s. The PHELIX system is designed to be compatible with the Los Alamos proton radiography facility. Initial experiments with PHELIX explore shocked-ejected particle transport into gas in converging geometries. For these experiments a liner-on-target configuration is employed. To control the initial conditions, micron-sized tungsten particles are used in place of shock-formed ejecta. The inner surface of the cylindrical target is coated with a 0.1 mm uniform layer of W powder. The liner impacts the target generating a shock that launches the W particles off the target surface. The time history of the trajectory of the shocked-ejected particulate is captured in 21 proton radiographs recorded during the experiment. Comparison of 3 experiments, one into vacuum, one into Ar at 8.3 bars and one into Xe at 8.3 bars are discussed. Results are compared to simulations. [Preview Abstract] |
Monday, June 15, 2015 2:45PM - 3:00PM |
D1.00003: Initial isentropic compression experiments on the MACH facility S.N. Bland, K.H. Kwek, K. Omar, S. Stafford, J. Winters, G. Wang We report on the first isentropic compression experiments performed on the MACH -- Mega Ampere Compression and Hydrodynamics -- facility at The Institute of Shock Physics. MACH is based around a 2MA, 400ns, ``dry air'' Linear Transformer Driver, which can be readily expanded to higher currents and drive voltages. In these initial experiments strip line loads of varying geometries were used to optimize both the peak magnetic pressure exerted on a target and the uniformity of the drive across samples. The use of a novel ``2 part target'' design was explored to reduce costs; and the ability of the machine to operate without insulator material -- using just `magnetic insulation' in vacuum -- was examined. In all cases multiple point frequency shifted Het-V, and/or line VISAR measurements were used to analyze the results. In a set of proof of principle experiments, the strength of different copper alloys is being explored, and we will then use MACH to examine the effect of micro-structure on the strength of NiTi alloys. We will discuss future experimental plans, including the use of hard X-rays generated by a portable X-pinch driver to perform in-situ diffraction measurements of samples under pressure. [Preview Abstract] |
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