Bulletin of the American Physical Society
2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005; Denver, Colorado
Session UO1: HEDP Science |
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Chair: Christopher Deeney, Sandia National Laboratories Room: Adam's Mark Hotel Governor's Square 10 |
Friday, October 28, 2005 9:30AM - 9:42AM |
UO1.00001: Equation of State Measurements in Ta$_{2}$O$_{5}$ Foams J.E. Miller, T.R. Boehly, D.D. Meyerhofer, J.H. Eggert, G.W. Collins The equation of state of Ta$_{2}$O$_{5}$ foam was measured using laser-driven shock compression at the OMEGA Laser Facility. Foams with densities in the range of 0.15 to 0.5 g/cc were shock-compressed with pressures of 100 to 400 GPa. Shock velocities and temperatures were measured on subnanosecond time scales. Comparisons between these experimental results and the existing QEOS model for this material will be discussed, as will the characterization of the foam samples. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Friday, October 28, 2005 9:42AM - 9:54AM |
UO1.00002: Novel diagnostic of shock fronts in solid materials M. Koenig, A. Ravasio, A. Benuzzi-Mounaix, N. Ozaki, B. Loupias, M. Borghesi, C. Cecceti, L. Romagnani, A. Schiavi, T. Boehly, A. macKinnon, P. Patel, D. Hicks, H.S. Park, S. Lepape, R. Clark, E. Henry, M. Notley We performed an experiment using high-energy protons and hard X-rays to characterize \textit{in situ }the spatial and temporal evolution of a laser-driven shock propagating through a solid material. Shock strength was inferred from shock velocity measurements using a self-emission diagnostic. The transverse high-energy proton beam was generated using a short intense laser beam on a gold backlighter foil. Due to high level scattering, proton beam was only used on a low Z target (CH or C foam). For higher Z material (aluminum), an hard x-ray ``1D'' backlighter (K-$\alpha $ source of Molybdenum at 17 keV) was obtained using small-edge-on foils. Time evolution of a shock front propagating into both materials C foam and aluminum will be presented. [Preview Abstract] |
Friday, October 28, 2005 9:54AM - 10:06AM |
UO1.00003: MBAR Shock Measurements in Copper-Doped Beryllium Driven by $\sim$50-EV Methane-Filled Halfraums T.E. Tierney, B.G. DeVolder, D.C. Swift, J.A. Cobble, D.L. Paisley, N.M. Hoffman, S.R. Goldman, W. Armstrong, J. Miller, T.R. Boehly, C. Sorce 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 $150 eV. VISAR measurements recorded shocks of approximately 1 Mbar. Measurements by a streaked optical pyrometer indicated that preheat was present for 30-40 micron thick samples within 1-ns of the start of the drive. We will present our data and analysis in comparison to as-shot simulations. *Work performed under U.S. DOE contract W-7405-ENG-36. LA-UR-05-5558 [Preview Abstract] |
Friday, October 28, 2005 10:06AM - 10:18AM |
UO1.00004: Material Strength in Vanadium Stephen Pollaine, Robert Cavallo, Thomas Lorenz, Bruce Remington, Ed Alley, David Bailey Preliminary results of measurements of vanadium strength at 600 kb and 1 Mb, at strain rates between 10$^7$/s and 10$^8$/s, are inconsistent with the Steinberg-Guinan [1] model, which is independent of strain rate, but can be made consistent with other models, such as PTW [2]. We compare several different strength models to the data. \newline \newline [1] DJ.Steinberg, S.G.Cochran, and M.W.Guinan, J. Appl. Phys. 51, 1498 (1980). \newline [2] D.L. Preston, D.L.Tonks, and D.C. Wallace, J. Appl. Phys. 93, 211 (2003). [Preview Abstract] |
Friday, October 28, 2005 10:18AM - 10:30AM |
UO1.00005: Laser-driven flyer impact experiments on LULI 2000 facility Norimasa Ozaki, M. Koenig, A. Benuzzi-Mounaix, T. Vinci, A. Ravasio, S. Le Pape, M. Esposite, W. Nazarov, E. Henry, G. Huser, M. Yoshida, K. Nagai, K.A. Tanaka Laser-driven flyer impact experiments have been performed at the LULI. Powerful lasers can launch much faster projectile than with conventional pulse powers, the impact technique generating extreme conditions in materials. Additionally, recent experiments have demonstrated that the scheme allows us to access very interesting states in material phase space. In present experiments, three types of targets; single flyer, multi-layered, and foam-buffered high-Z metal, were used. Impacted conditions in quartz were measured with rear-side (2 VISARs and SOP) and transverse diagnostics (shadowgraph). In the foam-buffered target, Ta foil was accelerated up to a velocity of 45 km/s. Shock wave gradually accelerated in quartz by flyer impact was generated, and the shock wave passing a distinct boundary to a conductive state was directly observed. This method is a way to produce very unique conditions in EOS diagram of material. [Preview Abstract] |
Friday, October 28, 2005 10:30AM - 10:42AM |
UO1.00006: Optical Measurements of Preheated Polystyrene and Aluminum Layers W. Theobald, J.E. Miller, T.R. Boehly, E. Vianello, I.V. Igumenshchev, V.N. Goncharov, A.V. Maximov, T.C. Sangster We present optical measurements of polystyrene and aluminum layers modified by ionizing radiation within a 100-ps time scale. The experiments were performed at the OMEGA Laser Facility using high-energy, 100-ps, 5 $\times $ 10$^{14}$ W/cm$^{2}$ laser pulses impinging onto a 40-\textit{$\mu $}m plastic ablator in order to generate the preheat radiation. Two temporal resolving optical diagnostics, a velocity interferometer for any reflector (VISAR), and a temperature-calibrated streaked optical pyrometer (SOP) measure the change of the optical properties and the temperature increase of samples mounted on the target's back side. Preheating prior to the arrival of a shock front is observed for the aluminum and plastic layers. Within the laser interaction time, a strong absorption and a frequency shift of the optical probe laser reflecting from the samples are measured with VISAR. The SOP measurement indicates temperatures of up to $\sim $4 eV at the target's back side prior to the shock front arrival. The experimental results are compared to one-dimensional hydrodynamic simulations with the code \textit{LILAC}. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Friday, October 28, 2005 10:42AM - 10:54AM |
UO1.00007: Measurements of $T_{e}$ and $Z$ in Direct-Drive, Shock-Heated Planar Targets H. Sawada, S.P. Regan, T.R. Boehly, I.V. Igumenshchev, V.N. Goncharov, F.J. Marshall, B. Yaakobi, T.C. Sangster, D.D. Meyerhofer, G. Gregori, D.G. Hicks, S.H. Glenzer, O.L. Landen The shell conditions in a direct-drive imploding capsule encompass many states of matter (i.e., Fermi degenerate to strongly coupled and ideal plasmas). Spectrally resolved x-ray scattering is used to infer $T_{e}$ and $Z$ in planar CH foils irradiated with peak intensities up to 1 $\times $ 10$^{15}$ W/cm$^{2}$, generating drive pressures in the 5 to 50 Mbar range. Just after shock breakout, the uniformly compressed portion was irradiated with 9.0 keV x rays from a Zn backlighter. The x rays scattered at either 90\r{ } or 120\r{ } were dispersed with a Bragg crystal and recorded with an x-ray framing camera. The $T_{e}$ and $Z$ inferred from spectral line shapes of the elastic Rayleigh and inelastic Compton components will be presented and compared with other diagnostic techniques. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Friday, October 28, 2005 10:54AM - 11:06AM |
UO1.00008: Spaced Nano-Foil Laser Targets as Bright High-Energy X-ray Sources J.D. Colvin, J.M. McNaney, J.L. Porter, L.E. Ruggles Colvin and Felter (Bull. A.P.S. 48/7. 288, 2003) first showed the feasibility of using very low-density (density $\sim $0.1{\%} solid) pure-metal foams as bright high-energy x-ray sources based on simulations of K-shell x-ray output under high-power laser illumination. They also presented preliminary results of a novel fabrication process for making such very low-density foams (Bull. A.P.S. 49/8, 285, 2004). In this talk we present some results of an intermediate step: fabrication of spaced nano-foil targets, simulations of how these targets turn into a near-homogeneous under-dense plasma when illuminated by a high-power laser, and spectroscopic measurements taken on the Z-Beamlet laser at Sandia National Laboratories. Preliminary results suggest that it may be possible to get a higher x-ray conversion efficiency from these targets than from a solid metal disc under identical illumination conditions. [Preview Abstract] |
Friday, October 28, 2005 11:06AM - 11:18AM |
UO1.00009: Ultrahigh-speed plasma sources and liner compression of high-temperature plasma P.J. Turchi The Open Fire series of multi-megampere experiments\footnote{P.J. Turchi, et al, ``Generation of High Energy X-Radiation Using a Plasma Flow Switch,'' JAP 69 (4), 1999.} on the Shiva Star capacitor bank achieved a megajoule of aluminum and (separately) tungsten ions at flow speeds in excess of 2000 km/s, corresponding to ion energies of 0.54 and 3.7 MeV, respectively. For the same kinematics, and pulser operation, the total flow energy would remain a MJ and the average ion energy for a DT plasma (at 2.5 AMU) would be 50 keV. These values suggest the possibility of ``isothermal'' compression by liner implosion to interesting particle densities at fusion-level temperatures. Based on the Open Fire experiments, the initial plasma density would be 10$^{17}$ cm$^{-3}$ in a volume of 1500 cm$^{3}$ at a temperature of 16 keV (after sharing energy with electrons). A 3-D liner implosion of about 5 MJ could isothermally compress this plasma to 10$^{20}$ cm$^{-3}$, with a dwell time at high density of about a microsecond, providing an n$\tau $-product of 10$^{14}$ s/cm$^{3}$. Such experiments, in which heat-loss actually helps, are within range of present systems, e.g., Shiva Star and Atlas. [Preview Abstract] |
Friday, October 28, 2005 11:18AM - 11:30AM |
UO1.00010: Longitudinal compression of an ion beam in the NDCX experiment Dale Welch, Carston Thoma, Prabir Roy, Enrique Henestroza, Simon Yu, Adam Sefkow Heavy ion fusion and ion-driven high energy density physics require the acceleration, compression, and transverse focusing of an intense ion beam. Neutralized drift compression of an ion beam makes use of a temporal velocity tilt and a neutralizing plasma to achieve small pulse lengths.[1] Here, we consider the neutralized drift compression experiment (NDCX at Lawrence Berkeley National Laboratory) in which a 300 keV, 25-milliamp K$^{+}$ ion beam is given a 150-keV head-to-tail energy variation using a tilt core induction cell. Pulse compression and focusing are achieved in the presence of a neutralizing plasma. Given adequate charge neutralization, the compression ratio is limited only by the accuracy of the applied velocity tilt and longitudinal temperature of the beam. Compression ratios exceeding 50 have been measured in agreement with particle-in-cell simulations. [1] D. R. Welch, D. V. Rose, T. C. Genoni, S. S. Yu and J. J. Barnard, Nucl Instrum. and Meth. Phys. Res. A 544, 236-242 (2005). [Preview Abstract] |
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