Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session NO4: Implosions and Symmetry |
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Chair: Peter Amendt, Lawrence Livermore National Laboratory Room: Plaza D |
Wednesday, November 13, 2013 9:30AM - 9:42AM |
NO4.00001: Performance of DT layered implosions on the NIF Pravesh Patel, Paul Springer, Charles Cerjan, Tammy Ma, Niko Izumi, Daniel Clark, Brian Spears, Michael Key, Nino Landen, John Lindl, John Edwards We describe the performance of indirectly-driven deuterium-tritium (DT) layered target experiments conducted on the National Ignition Facility (NIF) in terms of the experimentally derived thermodynamic properties of the hot spot and dense fuel at stagnation. An isobaric model of the assembled fuel is constructed with data from an array of nuclear and x-ray diagnostics providing absolute, spatial, temporal, and spectral information, and is used to determine the fuel pressure, volume, and energy. The model accounts for the possible presence of CH ablator mixed into the hot spot, which has the signature of enhanced radiation energy loss. This mix mechanism is found to be a principal contributor to the large variation in the neutron yield over clear (YOC) observed across the campaign. Achieving the hot spot conditions necessary for significant alpha heating and ignition requires the efficient conversion of the shell kinetic energy to thermal energy of the DT fuel at stagnation. In high convergence implosions the thermal energy of the fuel at stagnation is inferred to be $\sim$60{\%} of the delivered energy, and energies of $\sim$1.5-1.8 kJ have been achieved in the hot spot, approximately 30-40{\%} of that required for ignition. Performance metrics will be compared across a range of implosions varying in velocity, adiabat, and convergence ratio. [Preview Abstract] |
Wednesday, November 13, 2013 9:42AM - 9:54AM |
NO4.00002: ABSTRACT WITHDRAWN |
Wednesday, November 13, 2013 9:54AM - 10:06AM |
NO4.00003: Indirect cryogenic DT layered implosion performance with high-foot high-adiabat drive Hye-Sook Park, O.A. Hurricane, D.A. Callahan, E.L. Dewald, D.R. Dittrich, T. Doeppner, D.E. Hinkel, L.F. Berzak Hopkins, S. Le Pape, T. Ma, A.J. Mackinnon, P.K. Patel, B.A. Remington, H.F. Robey, J.D. Salmonson, J.L. Kline We are performing cryogenic DT layered implosion experiments on NIF using a 3-shock high-foot (high-adiabat) drive. This platform is designed to give a more robust implosion that is more resistant to high-mode ablation front Rayleigth-Taylor instabilities and is less sensitive (in models) to variations in opacity modeling of the capsule ablator. The initial NIF results show that the performance parameters are very close to 1D predictions and the measured mix-mass was low implying YOC \textgreater\ 50{\%}. In a follow-on shot, low-mode asymmetries in the formation of the DT ice layer degraded the yield by a factor of 2 indicating that the high-foot platform is less subject to the high-mode instabilities but the low-mode plays an important role in the implosion. This paper will present the experimental results of the high-foot DT layered shots from NIF. [Preview Abstract] |
Wednesday, November 13, 2013 10:06AM - 10:18AM |
NO4.00004: Inferring time dependent drive-induced low mode shape asymmetries in NIF implosions Andrea Kritcher, Dan Clark, Richard Town, Brian Spears, Steve Haan, Dave Bradley One of the most challenging tasks in ICF experiments is achieving adequate symmetry of the DT fuel and hot spot at high convergence ratios relevant for ignition. In addition, maintaining symmetry throughout the entire implosion is key for the efficient conversion of kinetic energy to compression and heating of the fuel and hot spot. In the recent shape campaign at NIF there has been an extensive effort to measure low mode asymmetries at various times during the implosion. In this talk, sensitivities of key performance metrics to applied low mode drive asymmetries will be discussed. These calculations have been preformed using the rad-hydro code HYDRA, in capsule only simulations, which enables controlled application of drive asymmetries vs time. This work includes single mode, time varying, and multi-mode perturbations. Post processing of key diagnostics will be presented. Using the predicted responses of these diagnostics, a model for obtaining drive asymmetries vs time that reproduces the recent measurements has been constructed. Prepared by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, November 13, 2013 10:18AM - 10:30AM |
NO4.00005: Diagnosing in-flight $\rho$R implosion asymmetry at low and intermediate mode numbers with charged particles at the NIF A. Zylstra, F. Seguin, C.K. Li, J. Frenje, N. Sinenian, M. Rosenberg, H. Rinderknecht, M. Manuel, M. Gatu Johnson, R. Petrasso, P. Amendt, R. Bionta, D. Bradley, D. Callahan, S. Friedrich, S. Glenn, R. Heeter, D. Hicks, N. Izumi, O. Landen, R. London, A. Mackinnon, N. Meezan, S. Weber J. DELETTREZ, V. GLEBOV, P. RADHA, T. SANGSTER, LLE, R. OLSON, SNL, J. KLINE, G. KYRALA, R. LEEPER, D. WILSON, LANL, J. KILKENNY, A. NIKROO, GA -- The Wedge Range Filter (WRF) proton spectrometers were developed for OMEGA and transferred to the NIF as National Ignition Campaign (NIC) diagnostics. In tuning-campaign implosions containing D and $^{3}$He gas, the WRFs are used to measure the spectrum of protons from D-$^{3}$He reactions. From the measured energy downshift of these protons, the total $\rho $R is inferred through the plasma stopping power. Data from WRFs fielded simultaneously on the pole and equator indicate low-mode polar $\rho $R asymmetries at shock burn. Significant swings in $\rho $R P2/P0 are also observed in the ignition campaign data set, attributed to low-mode x-ray drive inhomogeneity. The data set also allows studies of intermediate mode symmetry. This work was supported in part by the U.S. DOE, LLNL and LLE. [Preview Abstract] |
Wednesday, November 13, 2013 10:30AM - 10:42AM |
NO4.00006: Analysis of pinhole spatially-resolved spectra from Ti-doped implosions at OMEGA Tirtha Joshi, Heather Johns, Daniel Mayes, Tunay Durmaz, Roberto Mancini, Riccardo Tommasini, Sean Regan, Jacques Delettrez, Taisuke Nagayama We discuss the observation and analysis of spectrally-resolved images from direct-drive OMEGA implosions. The targets were deuterium filled, spherical plastic shells of varying thicknesses and gas pressures with a submicron Ti-doped tracer layer at the fuel-shell interface. The Ti spectral signature is primarily observed at the collapse of the implosion and recorded with a streaked spectrometer and three identical gated, multi-monochromatic imager (MMI) instruments fielded along quasi-orthogonal lines-of-sight. Both streaked and gated data show simultaneous emission and absorption spectral features associated with Ti K-shell line transitions. The spectrally-resolved images recorded with MMI were processed to obtain narrow-band images\footnote{T. Nagayama, et al, J. App. Phys. \textbf{109}, 093303 (2011).} and spatially-resolved spectra characteristic of contour regions on the image\footnote{T. Nagayama, et al, Phys. Plasmas \textbf{19}, 082705 (2012).} Two different spectroscopic methods were used to extract electron temperature and density, and mixing of the Ti into the core. Results are presented for experiments performed with different shell thicknesses, filling pressures and laser pulse shapes. [Preview Abstract] |
Wednesday, November 13, 2013 10:42AM - 10:54AM |
NO4.00007: First quantitative measurements of charged-particle stopping and its dependence on electron temperature and density in Inertial-Confinement-Fusion plasmas J. Frenje, C.K. Li, F. S\'eguin, A. Zylstra, H. Rinderknecht, R. Petrasso, J. Delettrez, V. Glebov, T. Sangster We report on the first quantitative measurements of charged-particle stopping in Inertial-Confinement-Fusion (ICF) plasmas at various conditions. In these experiments, four charged fusion products from the DD and D$^{3}$He reactions in D$^{3}$He gas-filled filled implosions were used to determine the stopping power of ICF plasmas at electron temperatures ($T_{e})$, ion temperatures ($T_{i})$, and areal densities ($\rho R)$ in the range of 0.6-4.0 keV, 3-14 keV and 2-10 mg/cm$^{2}$, respectively. The resulting data, in the form of measured energy downshift of the charged fusion products, clearly indicate that the stopping-power function depends strongly on $T_{e}$. It was also observed that the stopping-power function change in characteristics for higher-density implosions in which ions and electrons equilibrate faster, resulting in higher $T_{e}$ relative to $T_{i}$ and higher $\rho R$s. These results will be modelled by Landau-Spitzer theory and contrasted to different stopping-power models. This work was partially supported by the US DOE, NLUF, LLE, and GA. [Preview Abstract] |
Wednesday, November 13, 2013 10:54AM - 11:06AM |
NO4.00008: Simultaneous measurements of the D3He-p and DD-n burn history for studies of species separation in shock-driven implosions at OMEGA H. Sio, M. Rosenberg, A. Zylstra, F. Seguin, H. Rinderknecht, J. Frenje, M. Gatu Johnson, C.K. Li, R. Petrasso, C. Bellei, P. Amendt, S. Wilks, C. Stoeckl, V. Glebov, J. Delettrez, R. Betti, D. Meyerhofer, T. Sangster, N. Hoffman, G. Kagan, K. Molvig Simultaneous measurements of the D3He-p and DD-n burn histories have been conducted for studies of species separation in D3He shock-driven implosions at OMEGA. This measurement was facilitated by the recent upgrade to the Particles Temporal Diagnostic (PTD), which significantly improved the dynamic range and reduced the timing uncertainty. The measured difference between the D3He-p and DD-n bang time is contrasted to single- and multi-fluid 1-D hydro simulations and Particle-In-Cell (PIC) simulations. This work was supported in part by the U.S.LLNL, LLE, and DOE NNSA SSGF. [Preview Abstract] |
Wednesday, November 13, 2013 11:06AM - 11:18AM |
NO4.00009: Status of Ignition Hydro-Equivalent Implosion Performance on OMEGA T.C. Sangster, V.N. Goncharov, P.B. Radha, R. Betti, T.R. Boehly, C.J. Forrest, D.H. Froula, V.Yu Glebov, S.X. Hu, I.V. Igumenshchev, F.J. Marshall, R.L. McCrory, P.W. McKenty, D.D. Meyerhofer, D.T. Michel, C. Stoeckl, J.A. Frenje, M. Gatu-Johnson Demonstrating ignition hydro-equivalence with symmetric implosions on OMEGA is a likely prerequisite for proceeding with a polar-drive--ignition campaign on the National Ignition Facility. Ignition hydro-equivalent performance is defined by using metrics such as the peak pressure in the core, the primary neutron yield, and the fuel areal density during the burn. Hydrodynamic and laser-driven instabilities limit implosion performance with cryogenic DT fuel on OMEGA. Hydro instabilities are seeded by laser imprint and imperfections on the various target surfaces; these perturbation seeds can largely be controlled. Laser-driven instabilities including cross beam and two-plasmon decay reduce the drive pressure and compressibility of the fuel, respectively. Understanding and mitigating these laser--plasma instabilities will be required to reach full-ignition, hydro-equivalent performance on OMEGA. The latest results from cryogenic DT implosions will be presented and discussed in terms of the primary design parameters and current mitigation efforts for hydro and laser-driven instabilities. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, November 13, 2013 11:18AM - 11:30AM |
NO4.00010: A Pressure Diagnostic Based on X-Ray Continuum Images of Compressed Isobaric Hydrogen Implosion Cores R. Epstein, F.J. Marshall, V.N. Goncharov, R. Betti, R. Nora, A.R. Christopherson, I.E. Golovkin, J.J. MacFarlane Pressure is the quantity that best characterizes isobaric implosion cores, and it is a key parameter in quantifying their near-ignition performance. At high spectral energy, where the free--free (FF) emission from an imploded hydrogen core is optically thin, the FF emissivity profile can be obtained from an image by Abel inversion. This emissivity, which can be modeled accurately under hot-core conditions, is strongly temperature and density dependent. With a spectral response function matched to the temperature range anticipated for the hot spot at the time of peak emission, however, the imaged intensity becomes a function of the core pressure profile with very weak temperature dependence. In this way, the measured FF emissivity profile becomes a direct measure of the core pressure profile at the time of peak emission, as well as a test of the isobaric assumption. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Wednesday, November 13, 2013 11:30AM - 11:42AM |
NO4.00011: Search for reaction-in-flight neutrons using thulium activation at the National Ignition Facility Gary Grim, Robert Rundberg, Anton Tonchev, Malcolm Fowler, Jerry Wilhelmy, Tom Archuleta, Richard Bionta, Mitzi Boswell, Julie Gostic, Jeff Griego, Kenn Knittel, Andi Klein, Ken Moody, Dawn Shaughnessy, Carl Wilde, Charles Yeamans We report on measurements of reaction-in-flight (RIF) neutrons at the National Ignition Facility. RIF neutrons are produced in cryogenically layered implision by up-scattered deuterium, or tritium ions that undergo subsequent fusion reactions. The rate of RIF neutron production is proportional to the fuel areal density ($||$R) and ion-stopping length in the dense fuel assembly. Thus, RIF neutrons provide information on charge particle stopping in a strongly coupled plasma, where perturbative modeling breaks down. To measure RIF neutrons, a set of thulium activation foils was placed 50 cm from layered cryogenic implosions at the NIF. The reaction $^{169}$Tm(n,3n)$^{167}$Tm has a neutron kinetic energy threshold of 14.96 MeV. We will present results from initial experiments performed during the spring of 2013. Prepared by LANL under Contract DE-AC-52-06-NA25396, TSPA, LA-UR-13-22085. [Preview Abstract] |
Wednesday, November 13, 2013 11:42AM - 11:54AM |
NO4.00012: Polarization Measurements of Backscatter on NIF David Turnbull, John Moody, Jean-Michel Di Nicola, Laurent Divol, Denise Hinkel, Robert Kirkwood, William Kruer, Brian MacGowan, Ken Manes, Pierre Michel, Joseph Ralph, Ed Williams Time integrated, spatially localized measurements of the polarization of backward Stimulated Brillouin Scattering (SBS) collected by a Full Aperture Backscatter (FABS) diagnostic have been made on the National Ignition Facility (NIF). Early data from a variety of hohlraum experiments reveal that the backscatter polarization can differ significantly from that of the incident beam. Explanations for this include: more divergent backscatter from neighboring beams that have an orthogonal polarization; Crossed Beam Energy Transfer (CBET) from beams in the outer cones on NIF with polarizations that are tilted with respect to the measured beam, or even beams with nearly orthogonal polarizations (normally assumed to be non-interacting) that scatter from the beat waves driven between other pairs of beams (so-called Brillouin enhanced four-wave mixing); and Faraday rotation caused by laser generated magnetic fields within the target plasma. Preliminary analysis indicates that the dominant effect is the wider divergence of neighboring beams' backscatter. We will discuss the measurements and modeling, and also compare with previous results. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, November 13, 2013 11:54AM - 12:06PM |
NO4.00013: The Rocket Equation Improvement under ICF Implosion Experiment Yanbin Wang, Zhijian Zheng The ICF explosion process has been studied in details. The rocket equation has been improved in explosive process by introducing the pressure parameter of fuel. Some methods could be drawn by the improved rocket equation. And the methods could be used to improve ICF target design, driving pulse design and experimental design. The First is to increase ablation pressure. The second is to decrease pressure of fuel. The third is to use larger diameter of target sphere. And the forth is to a shorten driving pulse. [Preview Abstract] |
Wednesday, November 13, 2013 12:06PM - 12:18PM |
NO4.00014: The impact of capsule ``tent'' thickness on interpreting low mode shape S.R. Nagel, J.R. Rygg, L.R. Benedetti, T. Ma, M.A. Barrios, S.W. Haan, B.A. Hammel, T. Doeppner, A.E. Pak, R. Tommasini, O.S. Jones, R.P.J. Town, D.K. Bradley The performance of ICF targets relies on the symmetric implosion of highly compressed fuel. X-ray area-backlit imaging is used to assess in-flight low mode 2D asymmetries of the shell. These time-resolved images of the shell exhibit features that can be related to the lift-off position of the membranes used to hold the capsule within the hohlraum. Here we describe a systematic study of this membrane or ``tent'' thickness and its impact on the measured low modes seen in in-flight and self-emission images. While the low mode amplitudes (particularly P2 and P4) are weakly affected by the tent in time-resolved, backlit data, we observe areal density variations consistent with the membrane. By contrast, time integrated self-emission images along the same axis exhibit a reversal in perceived P4 mode due to the growth of the tent seeded feature, which could explain prior inconsistencies between the in-flight P4 and core P4, leading to a reevaluation of optimum hohlraum length. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-640729 [Preview Abstract] |
Wednesday, November 13, 2013 12:18PM - 12:30PM |
NO4.00015: NIF symmetry capsule modeling S.V. Weber, D.T. Casey, J.E. Pino, D.P. Rowley, V.A. Smalyuk, B.K. Spears, R.E. Tipton NIF CH ablator symmetry capsules are filled with hydrogen or helium gas. SymCaps have more moderate convergence ratios $\sim15$ as opposed to $\sim35$ for ignition capsules with DT ice layers, and better agreement has been achieved between simulations and experimental data. We will present modeling of capsules with CD layers and tritium fill, for which we are able to match the dependence of DT yield on recession distance of the CD layer from the gas. We can also match the performance of CH capsules with $D^3He$ fill. The simulations include surface roughness, drive asymmetry, a mock-up of modulation introduced by the tent holding the capsule, and an empirical prescription for ablator-gas atomic mix. [Preview Abstract] |
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