Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session YO5: ICF X-ray Measurements |
Hide Abstracts |
Chair: James Knauer, University of Rochester Room: 552AB |
Friday, November 2, 2012 9:30AM - 9:42AM |
YO5.00001: Using Orthogonal Images to Infer Spatial Variations in Opacity of Remaining Ablator and Fuel Mass in Imploding Capsules Laura Robin Benedetti, David Bradley, Steven Glenn, Nobuhiko Izumi, Shahab Khan, George Kyrala, Tammy Ma, Art Pak, Vladimir Smalyuk, Riccardo Tommasini, Richard Town Experiments at the National Ignition Facility attempt to achieve laser-driven inertial confinement fusion by imploding a capsule of DT fuel. In order to achieve sufficient density and temperature to drive nuclear fusion, the imploding capsule must be both highly convergent and highly symmetric. X-ray self-emission from imploding capsules is imaged for size and symmetry along two orthogonal axes by time-integrated (image plates) and time-resolved (framing cameras) diagnostics. Differences in emission along these axes indicate either an anisotropic hot core or anisotropy in total optical depth of the remaining ablator and fuel mass. We compare integrated emission intensity along a common-line-of-sight to further remove the ambiguity between anisotropy of emission and absorption. While we find good correlation for some recent NIF implosions (indicating isotropic or optically thin remaining mass), we find significant variations for others, suggesting an observable anisotropy in the thickness or density of the remaining mass. These results may help explain observations of asymmetric neutron yield. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, LLNL-ABS-564186. [Preview Abstract] |
Friday, November 2, 2012 9:42AM - 9:54AM |
YO5.00002: Measurements of Peak X-ray Emission of imploding DT capsules using X-ray Diagnostics at the National Ignition Facility Shahab Khan, Andrew MacPhee, Nobuhiko Izumi, Steve Glenn, Joe Kimbrough, Hans Herrmann, Jennifer Church, Perry Bell, David Bradley The absolute time (bang time) and burn width of the x-ray emission from the imploding cores of deuterium-tritium capsules near peak compression are measured by several different but complimentary diagnostic instruments. These instruments report independent measurements for the bang time (BT) and burn width (BW). A summary of the results from recent DT experiments is presented contrasting the BT and BW reported by: SPIDER, an x-ray streak camera; Gamma Ray History, a gamma ray detector; and Hardened X-ray Gated Imager (HGXI), a gated micro-channel plate coupled to film camera. An evaluation of the shielding and design of the instruments is presented in order to compare the spectral sensitivity of the instruments. Simulations of the x-ray emission spectrum are examined with the results reported by these x-ray diagnostics. [Preview Abstract] |
Friday, November 2, 2012 9:54AM - 10:06AM |
YO5.00003: Absolute K-shell emission line brightness measurements of laser-irradiated targets at the National Ignition Facility (NIF) M.A. Barrios, S.P. Regan, K.B. Fournier, M. May, J. Colvin, R. Olson, J. Kane, K. Widmann, D. Bradley, G.W. Collins X-ray K-shell-emission-line sources generated with under-dense laser-irradiated targets, including Ge and Zn pre-pulsed foils, Ge-doped silica aerogel, Kr gas targets, and a stainless-steel-lined cavity, were developed for radiographic and imaging applications on the NIF. Tailored laser pulses delivering up to 750 kJ of 3w light on target with peak laser power ranging from 14 to 150 TW were used to optimize laser-to-x-ray conversion efficiency (CE) for the various targets. The time-integrated, K-shell emission line brightness was measured using an absolutely calibrated, elliptically curved Bragg crystal spectrometer, measuring x rays between 6 and 16 keV. Absolute x-ray yields up to $\sim $10 kJ/sr for the He$_{\alpha }$ plus satellite emission from the mid-Z elements and corresponding CE up to 2.5{\%} into He$_{\alpha }$ and $\sim $6{\%} into 6.4-16 keV emission are reported and compared with simulated spectra. [Preview Abstract] |
Friday, November 2, 2012 10:06AM - 10:18AM |
YO5.00004: Development of Multi-keV X-Ray Backlighters for Implosion Experiments at the National Ignition Facility K.B. Fournier, M.A. Barrios, S.P. Regan, Y.P. Opachich, E. Dewald, R. Olson, J. Kane, K. Widmann, D. Farley, S. Ross, O. Landen, A. MacKinnon For ignition experiments at the National Ignition Facility, it is important to know the trajectory and velocity of the capsule's ablator shell, as well as the mass remaining in the ablator at times near peak compression. To make these measurements, high-photon-energy, bright x-ray backlighters are required. Backlighter targets composed of Zn (Z=30), Ge (Z=32) and Br (Z=35) were optimized as a function of target thickness and laser intensity for specific applications to 1-D streaked and 2-D gated radiography of imploding capsule shells. Work will continue with higher-Z foils, specifically Zr (Z=40) and Mo (Z=42) for radiographs of denser, more opaque material. Targets were driven with up to 2 NIF quads, delivering up to 60 kJ of 3$\omega$ laser energy. Intensity on target ranged from 5x10$^{14}$ to $\approx$1$\times$10$^{16}$ W/cm$^2$. We will present the streaked records of the x-ray power emitted from the target, the spectral content of the backlighter signal, and 2-D images of the backlighter emission. Comparison of the backlighter signal to hohlraum background will also be given. [Preview Abstract] |
Friday, November 2, 2012 10:18AM - 10:30AM |
YO5.00005: Bright X-ray Fe K-shell Source Development at the National Ignition Facility Mark May, K.B. Fournier, J. Colvin, M.A. Barrios, K. Widmann, R. Patterson, M. Schneider, S. Regan High conversion efficiency (CE) K-shell sources are being developed for High Energy Density (HED) experiments for use as backlighters and for the testing of materials exposed to high X-ray fluences. Recently, sources with high CE in the Fe K-shell have been investigated at the National Ignition Facility. These targets were 4.1 mm in diameter 4 mm tall hollow epoxy tubes having a 50 $\mu$m thick wall supporting a tube of 3.5 $\mu$m thick stainless steel. 160 of the NIF laser beams deposited 500 kJ of 3$\omega$ light into the target in a 150 TW 3.3 ns square pulse. This laser configuration sufficiently heated the target to optimize the K-shell emission. The absolute X-ray emission of the source was measured by two calibrated Dantes, which are filtered X-ray spectrometers. Time resolved and time integrated images filtered for the Fe K-shell were recorded to understand the heating of the target. Time integrated high resolution spectra were recorded in the K-shell range. Details of the experiment and CE's will be discussed. This work was done under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and Defense Threat Reduction Agency IACRO no. 11-4551l, ``Research Program for X-Ray Experimentation Cap [Preview Abstract] |
Friday, November 2, 2012 10:30AM - 10:42AM |
YO5.00006: Modeling of bright Fe K-shell emission from laser-irradiated targets and comparison to data J.D. Colvin, M.J. May, K.B. Fournier, M.A. Barrios, J. Kane, K. Widmann, R. Patterson, M. Schneider, S.P. Regan We used the ``high-flux'' model incorporated in a 2D radiation-hydrodynamics code to simulate the Fe K-shell emission from under-dense Fe plasmas created by laser-driven targets on both the Omega laser at the University of Rochester and the National Ignition Facility laser at LLNL. In the high-flux model, independently developed by Colvin et al. (Phys. Plasmas 17, 073111, 2010) and Rosen et al. (HEDP 7, 180, 2011), non-local electron thermal conduction is modeled in the Spitzer-Harm formulation with a large flux limiter, and ionization levels are computed in non-LTE with a Detailed Configuration Accounting atomic model specially constructed for the Fe K-shell. In this presentation we show the simulated emitted x-ray power vs time in several x-ray photon energy bands and the time-integrated emitted spectra, and compare these simulated results to the corresponding data from several actual Omega and NIF shots. [Preview Abstract] |
Friday, November 2, 2012 10:42AM - 10:54AM |
YO5.00007: Engineering of Laser Plasma Interaction for hard X ray source optimization Sebastein le Pape, Laurent Divol, Andrew Mackinnon, Dustin Froula, Tammy Ma, Riccardo Tommasini, Vladimir Glebov, Hans Herrmann, Jim McNanney, Stephan Friedrich, Jim Knauer, Hans Rinderknecht, Andrew Macphee, Joe Kilkenny, Craig Sangster Laser Plasma Interaction at intensities ranging from 7e17 W/cm$^{2}$ to 5 e16 W/cm$^{2}$ have been used on the NIF to increase X ray production above 40 KeV. Timing of nuclear diagnostics on the NIF requires a bright impulse of X rays above 40 KeV. To generate such an impulse we have used 88 ps, 50 to 100 Joules beams all overlapped onto a 2 mm silver disk. Intensity scaling have shown similar saturation trend as Two Plasmon Decay study (TPD) made on the Omega facility. Based on this observation, an experimental campaign has been carried out on Omega and NIF to optimize the hard X ray source by increasing hot electron production through TPD. Results of this campaign will be presented in this talk. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. [Preview Abstract] |
Friday, November 2, 2012 10:54AM - 11:06AM |
YO5.00008: Soft X-Ray Backlighting of Direct-Drive Implosions Using a Narrowband Crystal Imaging System C. Stoeckl, J.A. Delettrez, G. Fiksel, D. Guy, R.K. Jungquist, C. Mileham, P.M. Nilson, T.C. Sangster, M.J. Shoup III, W. Theobald X-ray backlighting of high-energy-density matter is widely used for imaging high-energy density plasmas in hydrodynamic experiments. High-energy petawatt (HEPW) lasers such as OMEGA~EP promise significantly improved backlighting capability by producing enhanced x{\-}ray power and shorter emission times. A narrowband x-ray imager with a spherically bent quartz crystal for the Si He$_{\alpha}$ line at $\sim $1.86 keV has been used to record backlit images of room-temperature direct-drive implosions driven by $\sim $15 kJ of UV (351-nm) laser light with a 1-ns pulse duration. The time-integrated images show a high signal-to-background ratio of $>$10:1 with backlighter laser energies of $\sim $1.5 kJ at a 10-ps pulse duration and a spatial resolution of better than 20 \textit{$\mu $}m. The signal recorded from the backlighter foil is within a factor of 2 of the core emission. Concepts to improve the performance of the imaging system and to adapt it to cryogenic target implosions will be presented. This work was supported by the U.S. Department of Energy under Cooperative Agreement Nos. DE-FC02-04ER54789 and DE-FC52-08NA28302. [Preview Abstract] |
Friday, November 2, 2012 11:06AM - 11:18AM |
YO5.00009: Time-Resolved X-Ray Brightness Measurements from Short-Pulse, Laser-Irradiated Thin Foils B. Eichman, W. Theobald, C. Stoeckl, C. Mileham, T.C. Sangster The production of soft x rays ($\sim $keV) from high-intensity, short-pulse laser plasmas is important for future applications such as backlighting cryogenic targets on OMEGA. The physics of short-pulse laser--plasma interactions and the coupling of laser energy into both the thermal plasma and fast electrons were studied to optimize x-ray production from mass-limited aluminum foil targets. Foil targets of various sizes from 50 to 500 \textit{$\mu $}m were irradiated with picosecond pulse duration laser pulses at intensities similar to OMEGA area backlighter schemes (10$^{18}$ to $>$10$^{19}$ W/cm$^{2})$. The time-resolved x-ray emission was measured with a conically curved crystal coupled with an ultrafast x-ray streak camera. The He$_{\alpha }$ and the Ly$_{\alpha }$ line emission from aluminum foils was spectrally measured and temporally resolved. In addition, the x-ray source was characterized with a calibrated time-integrated spectrograph and spatially resolved images were taken with a spherically curved Bragg crystal. The combination of these measurements allows the brilliance of the x-ray line source to be inferred. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Friday, November 2, 2012 11:18AM - 11:30AM |
YO5.00010: Performance characterization measurements of DIXI, a x-ray framing camera with a $<$10 ps gate Sabrina R. Nagel, P.M. Bell, D.K. Bradley, R.F. Smith, M.J. Ayers, B. Felker, G.W. Collins, T.J. Hilsabeck, J.D. Kilkenny, T. Chung, B. Sammuli, J.D. Hares, A.K.L. Dymoke-Bradshaw Modeling shows that for an igniting ICF capsule the brightness of the x-ray emission at bang time compromises the images around ($\pm$ 20 ps) bang time if gate times are longer than 10 ps. Here we present the latest characterization measurements for DIXI (dilation x-ray imager), a unique instrument that utilizes pulse-dilation technology [1] to achieve x-ray imaging with temporal gate times below 10 ps [2]. Time resolved x-ray measurements were conducted using the COMET laser facility at the Lawrence Livermore National Laboratory (LLNL). Results from these short pulse laser driven plasma experiments, in particular comparison measurements between two gate widths and the linearity along the active area, are given along with comparisons to gated x-ray imagers currently used at the NIF. LLNL is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. Work supported by U.S. Department of Energy under Contract DE-AC52-06NA27279. LLNL-ABS-564118\\[4pt] [1] T. J. Hilsabeck et. al., Rev. Sci. Instrum., 81, 10E317, (2010)\\[0pt] [2] S. R. Nagel et al., Rev. Sci. Instrum., accepted (2012) [Preview Abstract] |
Friday, November 2, 2012 11:30AM - 11:42AM |
YO5.00011: Quantitative K$\alpha$ line spectroscopy for energy transport in ultra-intense laser plasma interaction Z. Zhang, H. Nishimura, T. Namimoto, S. Fujioka, Y. Arikawa, M. Nakai, M. Koga, H. Shiraga, S. Kojima, H. Azechi, T. Ozaki, H. Chen, J. Pakr, G.J. Williams, M. Nishikino, T. Kawachi, A. Sagisaka, S. Orimo, K. Ogura, A. Pirozhkov, A. Yogo, H. Kiriyama, K. Kondo, Y. Okano X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes, for the detectors and crystal respectively. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for Au K$\alpha$ x-ray line emissions, is derived as a consequence of this work. By considering the hot electron temperature, the transfer efficiency from LFEX laser to Au plate target is about 8\% to 10\%. [Preview Abstract] |
Friday, November 2, 2012 11:42AM - 11:54AM |
YO5.00012: Optimization of 4.7keV X-ray Titanium Sources Driven by 100-ps Laser Pulse Jun Xiong, Jiaqing Dong, Guo Jia, Wei Wang, Sizu Fu, Wudi Zheng Experiment with thin titanium foils irradiated by two pulses delayed in time is conducted on the Shenguang-II laser facility. The prepulse induces an underdense plasma, after 2ns, the main pulse (\textit{$\lambda $}$_{L}$=0.35$\mu$m, $E_{L}\approx $120J, \textit{$\tau $}$_{L}\approx $100ps) is injected into the underdense and produced strong line emission from titanium $K-$shell (i.e., He$_{\alpha }$ at 4.7 keV). Data show that 4.7-keV x-ray emission with the prepulse is approximately two times more intense than that without the prepulse, and can be used as a backlighting source satisfying the diagnostic requirements for dense plasma probing. High quality plasma images are obtained with the backlighting 4.7 keV x-rays in a Rayleigh-Taylor hydrodynamic instability experiment. [Preview Abstract] |
Friday, November 2, 2012 11:54AM - 12:06PM |
YO5.00013: A Consistency Study for Manganese-He$_\alpha$ Emission with Z-Beamlet Matthias Geissel, Carlos Cox, I.C. Smith, J.E. Shores, V.H. Bigman, F.W. Long, B.W. Atherton Sandia National Laboratories' Z-Backlighter Facility is using a monochromatic X-ray crystal imaging concept at the Manganese He$_\alpha$ energy of 6.151\,keV to backlight HEDP experiments on the Z-Acelerator [1]. We will report on the first campaign dedicated to study and optimize the consistency of image brightness with respect to varying target and laser properties. It will be explained how physical insights and mechanical improvements are contributing to the continuous development of the backlighting capabilities and how they will feed back into the planning of the next optimization campaigns.\\[4pt] [1] D.B. Sinars, G.R. Bennett, D.F. Wenger et al.: Rev. Sci. Instrum., {\bf 75}/10, 3672 (2004) [Preview Abstract] |
Friday, November 2, 2012 12:06PM - 12:18PM |
YO5.00014: Experimental Investigation of X-ray Sources for Use in X-ray Thomson Scattering E.C. Harding, T. Ao, J.E. Bailey, S.B. Hansen, A.B. Sefkow, M.P. Desjarlais, R.W. Lemke, L.P. Mix, D.B. Sinars, I.C. Smith, G. Gregori X-ray Thomson Scattering (XRTS) measurements demand high-brightness x-ray probes due to the small scattering cross-sections of most materials. Using the Z-Beamlet laser we investigated several x-ray sources, and endeavored to determine the conditions of the emitting plasma so that we may optimize the x-ray production. The relative line intensities from measured spectra, as well as HYDRA simulations, were used to diagnose the temperature and density of the plasma. Future XRTS experiments on Z will require the use of a foam target in order to create a spatially resolvable scattering signal. In preparation for these experiments several undriven foam scattering experiments were conducted. These results as well as plans for the upcoming Z experiment will be presented. [Preview Abstract] |
Friday, November 2, 2012 12:18PM - 12:30PM |
YO5.00015: Improved Structure Factors for Modeling XRTS Experiments Liam Stanton, Michael Murillo, John Benage, Frank Graziani Characterizing warm dense matter (WDM) has gained renewed interest due to advances in powerful lasers and next generation light sources. Because WDM is strongly coupled and moderately degenerate, we must often rely on simulations, which are necessarily based on ions interacting through a screened potential that must be determined. Given such a potential, ionic radial distribution functions (RDFs) and structure factors (SFs) can be calculated and related to XRTS data and EOS quantities. While many screening models are available, such as the Debye- (Yukawa-) potential, they are known to over-screen and are unable capture accurate bound state effects, which have been shown to contribute to both scattering data from XRTS as well as the short-range repulsion in the RDF. Here, we present a model which incorporates an improvement to the screening length in addition to a consistent treatment of the core electrons. This new potential improves the accuracy of both bound state and screening effects without contributing to the computational complexity of Debye-like models. Calculations of ionic RDFs and SFs are compared to experimental data and quantum molecular dynamics simulations for Be, Na, Mg and Al in the WDM and liquid metal regime. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700