Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Plasma Physics
Volume 54, Number 15
Monday–Friday, November 2–6, 2009; Atlanta, Georgia
Session BO5: Hohlraum Physics |
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Chair: Mordecai Rosen, Lawrence Livermore National Laboratory Room: Hanover CDE |
Monday, November 2, 2009 9:30AM - 9:42AM |
BO5.00001: Lasnex Calculations of NIF Vacuum Hohlraum Experiments R.E. Olson, L.J. Suter, J.L. Kline, E.A. Williams, S.H. Glenzer, K. Widmann, D.A. Callahan, N.B. Meezan, S.H. Langer Lasnex calculations will be described and the results compared with experimental data for a series of NIF vacuum hohlraum experiments that were among the first targets shot on NIF as part of the facility commissioning. The pre-shot calculations predicted that the 6.40 mm long, 3.55 mm diameter hohlraums would be heated to peak radiation temperatures in the range of 225-275 eV using a 96 beam subset of the NIF laser beams (up to 350 kJ total on-target), and to a peak radiation temperature of 330 eV using all 192 NIF laser beams (700 kJ total). These 2 ns sq pulse, 3w drive energies are 10-20x the on-target energies used in previous hohlraum experiments at the Nova and Omega laser facilities. The new NIF hohlraum calculations and experimental data will be compared with previous (Omega/Nova) hohlraum calculations and data. This data will allow us to validate the Lasnex code and associated physics packages at the increased size and energy regimes now available for hohlraum experiments at the NIF. [Preview Abstract] |
Monday, November 2, 2009 9:42AM - 9:54AM |
BO5.00002: The Hohlraum Energetics experimental campaign on the National Ignition Facility S. Glenzer, J. Atherton, R. Berger, E. Dewald, L. Divol, S. Dixit, E. Dzenitis, D. Hinkel, D. Callahan, D. Kalantar, J. Kline, G. Kyralla, O. Landen, S. LePape, B. MacGowan, N. Meezan, P. Michel, J. Moody, E. Moses, L. Suter, R. Wallace, K. Widmann We will review progress in performing the hohlraum energetics experiments on the National Ignition Facility. The experiments are designed to first activate target diagnostics and to demonstrate target experiments with cryogenic targets. In particular, a series of hohlraum and gas-filled target shots will be fielded to demonstrate performance of the absolutely calibrated soft x-ray spectrometer, Dante, the laser backscatter suite of diagnostics, i.e., the full aperture backscatter station (FABS) and Near Backscatter Imager (NBI) on two cones of the 48 quads of beams, and the absolutely calibrated hard x-ray bremsstrahlung detector, FFLEX. The campaign is designed to demonstrate laser beam intensity and laser conditioning to efficiently heat ignition hohlraums to radiation temperatures required to drive ignition capsules with laser energies in the range of 1-1.5 MJ. In this talk, we will discuss progress towards fielding this campaign on the National Ignition Facility and describe our approach for selecting the radiation temperature for ignition hohlraums. [Preview Abstract] |
Monday, November 2, 2009 9:54AM - 10:06AM |
BO5.00003: Vacuum Hohlraum energetic experiments on the National Ignition Facility John Kline, S. Glenzer, K. Widmann, R. Olson, D. Hinkel, E. Williams, L. Suter, J. Celeste, E. Dewald, S. Dixit, W. Hsing, O. Landen, B. MacGowan, A. Warrick, J. Atherton, R. Berger, D. Callahan, L. Divol, C. Haynam, D. Kalantar, J. Kilkenny, S. Le Pape, D. Larson, N. Meezan, M. Schneider Results from vacuum hohlraum energetics experiments on the National Ignition Facility using a subset of NIF's 192 beams are presented. In these experiments, the scaling of radiation temperature for conventional gold hohlraums as well as gold hohlraums lined with a thin gold-boron liner was measured. These experiments are the first test of hohlraum drive scaling at $\sim $ 70{\%} of full-NIF scale. We show how these results compare with scalings~developed on predecessor facilities at a fraction of the laser energy being used here. In NIF ignition hohlraums, one of the mitigation strategies for SBS is to mix boron into the inner 0.6 $\mu$m of the Au hohlraum wall. These experiments also test if, as predicted by simulations, there is no anomalous degradation of the radiation temperature due to the gold-boron liner. [Preview Abstract] |
Monday, November 2, 2009 10:06AM - 10:18AM |
BO5.00004: High Resolution Integrated Hohlraum-Capsule Simulations for Virtual NIF Ignition Campaign O.S. Jones, M.M. Marinak, C.J. Cerjan, D.S. Clark, M.J. Edwards, S.W. Haan, S.H. Langer, J.D. Salmonson We have undertaken a virtual campaign to assess the viability of the sequence of NIF experiments planned for 2010 that will experimentally tune the shock timing, symmetry, and ablator thickness of a cryogenic ignition capsule prior to the first ignition attempt. The virtual campaign consists of two teams. The ``red team'' creates realistic simulated diagnostic data for a given experiment from the output of a detailed radiation hydrodynamics calculation that has physics models that have been altered in a way that is consistent with probable physics uncertainties. The ``blue team'' executes a series of virtual experiments and interprets the simulated diagnostic data from those virtual experiments. To support this effort we have developed a capability to do very high spatial resolution integrated hohlraum-capsule simulations using the Hydra code. Surface perturbations for all ablator layer surfaces and the DT ice layer are calculated explicitly through mode 30. The effects of the fill tube, cracks in the ice layer, and defects in the ablator are included in models extracted from higher resolution calculations. Very high wave number mix is included through a mix model. We will show results from these calculations in the context of the ongoing virtual campaign. [Preview Abstract] |
Monday, November 2, 2009 10:18AM - 10:30AM |
BO5.00005: NIF Ignition Hohlraum Designs With and Without Laser Entrance Hole Liners Debra Callahan, Denise Hinkel, Siegfried Glenzer, John Lindl, Nathan Meezan, Pierre Michel, Richard Town, Larry Suter The laser entrance hole (LEH) of the NIF ignition hohlraum has typically been lined with a thin ($\sim $ 30 micron) plastic liner. The purpose of this liner is to tamp the motion of the gold blow-off from the LEH lip. This simplifies symmetry optimization but increases the LEH plasma density. Single beam calculations of the expected laser-plasma interactions (LPI) show little gain in this region. However, multiple beam effects may amplify the single beam backscatter in the LEH. Reducing LEH plasma density by removing the liner reduces the multiple beam effects. To compensate for the LEH closure, the initial LEH is larger without the liner. This results in an increase in the laser power and energy required to drive the same capsule. In this talk, we will discuss designs with and without an LEH liner and how we will optimize the design based on the early hohlraum experiments on NIF. [Preview Abstract] |
Monday, November 2, 2009 10:30AM - 10:42AM |
BO5.00006: Tuning Implosion Symmetry on the National Ignition Facility S.V. Weber, D. Callahan, M.J. Edwards, N. Meezan, B. Spears, G. Kyrala, D.C. Wilson Implosion symmetry on the National Ignition Facility (NIF) will be achieved though experiments employing a series of surrogate capsules of increasing fidelity to the ignition target. Initial tuning will employ gas-filled symmetry capsules (SymCaps) of reduced size from the ignition targets. These are tuned to minimize asymmetry of the imploded core x-ray emission by varying hohlraum length, relative powers of the laser beam cones, and cone frequency difference. Later experiments, still at smaller scale, employ dudded-fuel capsules with reduced-deuterium THD ice layers, which are closer surrogates of the ignition capsule. The modest neutron yields of these targets are compatible with our full suite of x-ray diagnostics. Finally, full-size THD capsules will be tested, preparing us for ignition attempts with live DT fuel. Single parameter sensitivity studies have been used to set fabrication tolerances. [Preview Abstract] |
Monday, November 2, 2009 10:42AM - 10:54AM |
BO5.00007: The Use of Symcaps for Symmetry Tuning of Ignition Capsules George Kyrala, S.H. Glenzer, N.B. Meezan, S.V. Weber, L.J. suter, N. Izumi, D.A. Callahan, M.J. Edwards, O.L. Landen Symmetry tuning of the ICF imploding capsule has a great impact on the performance of capsule to eventually reach ignition. We will discuss the technique of using symcap capsules to measure the symmetry. In symcaps the DT is replaced by an equivalent ablator mass, are calculated to mimic the hydrodynamic behavior of the ignition capsule, and their x-ray emission signature correlates well with an ignition capsules' core shape. Due to their low convergence, symcaps have lower sensitivity to irradiation symmetry than ignition capsules. But, they still allow, initially, tuning the symmetry of an ignition capsule, without the complications of yield or cryogenics. We will describe the initial use of symcaps in NIF hohraums to measure the sensitivity of their shape to variations in the fraction of energy in each cone of the incident laser beams, and their use to tune the symmetry of the implosion. [Preview Abstract] |
Monday, November 2, 2009 10:54AM - 11:06AM |
BO5.00008: First re-emit experiments on the National Ignition Facility for early time symmetry tuning of indirect drive ignition implosions Eduard Dewald, Jose Milovich, Cliff Thomas, Steven Glenn, John Kline, Rahul Prasad, Otto Landen In indirect drive ignition experiments on the National Ignition Facility (NIF), the symmetry of the hohlraum radiation drive for the first 2 ns is tuned using the re-emit technique [1] which measures the instantaneous x-ray drive asymmetry based on soft (600-1200 eV) x-ray imaging of the re-emission of a high-Z sphere surrogate capsule. We performed multi-view re-emit symmetry experiments in 90{\%} scale NIF ignition vacuum hohlraums at 90-110 eV NIF foot radiation temperatures at the Omega facility. Compared to [1] these experiments use a less perturbing off-axis stalk rather than a thin CH tent to hold the capsule and have an azimuthal laser beam illumination similar to NIF. We measured radiation symmetry sensitivity to inner/outer beams power balance and we assessed the residual radiation asymmetry of the patched diagnostic holes and missing laser beams. We will also report on the first re-emit experiments performed recently on the National Ignition Facility in full ignition scale gas filled hohlraums. These experiments assess the effects on radiation symmetry and expected uncertainties of the technique due to the additional effects given by the hohlraum gas fill. [1] E.L. Dewald, \textit{et. al.,} Rev. Sci. Instrum. 79, 10E903, 2008. [Preview Abstract] |
Monday, November 2, 2009 11:06AM - 11:18AM |
BO5.00009: 3D studies of the NIF symmetry tuning targets J. Milovich, O. Jones, M. Edwards, S. Weber, E. Dewald, O. Landen, M. Marinak Minimizing radiation drive asymmetries is necessary for a successful ignition campaign. Since the ignition capsule symmetry is most sensitive to the foot (first 2 ns) and the peak of the laser pulse, two different targets will be fielded on the NIF: re-emit and symmetry capsules (Sym-Caps). The first measures the incoming flux asymmetries during the foot by observing the re-radiated flux of a high-Z ball in place of the ignition capsule. The Sym-Caps resemble the ignition target with the frozen DT layer replaced by an equivalent mass of ablator material, thus preserving the hydrodynamic implosion properties. By measuring the x-ray self-emission near peak compression the ignition capsule core shape can be tuned. Simulations with 2D radiation-hydrodynamic simulations codes omit 3D effects in the hohlraum such as diagnostic holes, capsule roughness, shot-to-shot variations caused by laser beam power imbalances and pointing errors. We study these effects by performing 3D simulations using HYDRA and found that tuning the laser pulse using a finite number of shots is not substantially compromised. [Preview Abstract] |
Monday, November 2, 2009 11:18AM - 11:30AM |
BO5.00010: 3-D simulations for assessment of NIF shock timing techniques H.F. Robey, R.E. Olson, O.S. Jones, J.L. Milovich, S.M. Sepke Capsule implosions planned for the National Ignition Facility (NIF) require a series of shocks, which propagate through the ablator and DT ice shell. The strength and timing of these shocks is critical for maintaining the DT fuel on a low adiabat. To meet the requirements, tuning experiments are being planned to measure and adjust the shock timing. These experiments use a modified target geometry that employs a re-entrant Au cone to provide optical access to the shocks in capsule interior. This modified geometry introduces some additional uncertainties, which are intrinsically three-dimensional in nature. Examples of 3D uncertainties include beam-to-beam power balance, pointing, and 3D fabrication features, all of which may have a greater impact on these localized shock timing measurements than they will have on the overall drive symmetry in the hohlraum. In order to assess the effect of these uncertainties, 3D simulations using HYDRA have been performed to test the robustness of the shock timing measurements. [Preview Abstract] |
Monday, November 2, 2009 11:30AM - 11:42AM |
BO5.00011: Optimizing implosion yields using rugby-shaped hohlraums Hye-Sook Park, H. Robey, P. Amendt, F. Philippe, A. Casner, T. Caillaud, J.-L. Bourgade, O. Landoas, C.K. Li, R. Petrasso, F. Seguin, M. Rosenberg, V. Yu. Glebov We present the first experimental results on optimizing capsule implosion experiments by using rugby-shaped hohlraums [1] on the Omega laser, University of Rochester. This campaign compared D$_{2}$-filled capsule performance between standard cylindrical Au hohlraums and rugby-shaped hohlraums for demonstrating the energetics advantages of the rugby geometry. Not only did the rugby-shaped hohlraums show nearly 20{\%} more x-ray drive energy over the cylindrical hohlraums, but also the high-performance design of the capsules provided nearly 20 times more DD neutrons than in any previous Omega hohlraum campaigns, thereby enabling use of neutron temporal diagnostics. Comparison with simulations on neutron burn histories, x-ray core imaging, backscattered laser light and radiation temperature are presented. [1] P. Amendt \textit{et al}., Phys. Plasmas 15, 012702 (2008) [Preview Abstract] |
Monday, November 2, 2009 11:42AM - 11:54AM |
BO5.00012: What measurements of proton self emission tell us about hohlraum fields and yield anomalies R. Petrasso, C. Li, F. Seguin, J. Frenje, M. Rosenberg, H. Rinderknecht, F. Philippe, A. Casner, T. Caillaud, O. Landoas, J.-L. Bourgade, P. Amendt, N. Izumi, J. Koch, O. Landen, J. Milovich, H. Park, H. Robey, R. Robey, R. Town, A. Nikroo, J. Kilkenny Measurements have been made of 14.7-MeV self-emission protons, from reactions of D-3He fuel, for a variety of hohlraums - scale 1 and scale $\raise.5ex\hbox{$\scriptstyle 3$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 3$} $, gold and cocktail hohlraums, vacuum and gas-filled hohlraums, cylindrical and rugby geometries, drive with and without phase plates, drive with different numbers of beams, and implosions with different capsule parameters. The picture that emerges is quite consistent: large anisotropies in the proton fluence pattern are generally observed out the LEH but little if any variations through the hohlraum equator. In addition, we examine whether the scaling of yields from pure D2 to D-3He mixtures is found to deviate from the expected density scaling (i.e. the Rygg Effect), as reported recently for directly driven capsules (1). (1) H. Herrmann \textit{et al}., PoP \textbf{16,} 056312(2009) [Preview Abstract] |
Monday, November 2, 2009 11:54AM - 12:06PM |
BO5.00013: Filamentation in the coronae of imploding ICF capsules F.H. Seguin, C.K. Li, M. Manuel, J.R. Rygg, J.A. Frenje, R.D. Petrasso, R. Betti, F.J. Marshall, D.D. Meyerhofer Electromagnetic fields associated with filamentary structures in the coronae of directly-driven ICF capsules have been studied with charged-particle radiography at the OMEGA laser facility. The time evolution and structures of the fields, including identification of field type, will be described on the basis of complementary radiographs recorded with several particle types as well as Monte-Carlo simulations. The particles include monoenergetic species (15-MeV protons, 3-MeV protons, and 3.6-MeV alpha particles, from laser-driven, imploding-pusher capsules with D$^{3}$He fill) as well as protons with exponential spectra (produced from short-pulse OMEGA-EP laser beams incident on a foil). Possible connections with specific hydrodynamic and/or laser-plasma-interaction instabilities, and implications for implosion physics, will be discussed. This work was performed at the LLE NLUF, and was supported in part by the FSC at U. of R., US DoE, LLNL, and LLE. [Preview Abstract] |
Monday, November 2, 2009 12:06PM - 12:18PM |
BO5.00014: Electromagnetic Fields and Plasma Flow in Laser-Irradiated Hohlraums at OMEGA C.K. Li, F.H. Seguin, J.A. Frenje, M.J. Rosenberg, R.D. Petrasso, P.A. Amendt, R.P.J. Town, O.L. Landen, J.L. Milovich, J.R. Rygg, R. Betti, J. Knauer, D.D. Meyerhofer, J.M. Soures, C.A. Back, J.D. Kilkenny, A. Nikroo We report on the first proton radiography of laser-irradiated hohlraums and of indirectly-driven capsule implosions in inertial confinement fusion (ICF). These experiments resulted in observations of self-generated electric and magnetic fields. Peak values are $\sim $ 10$^{9}$ V m$^{-1}$ and $\sim $ 10$^{6}$ gauss. Time-gated radiographs of monoenergetic protons with discrete energies (15.0 and 3.3 MeV) reveal dynamic pictures of field structures and plasma flow. Near the end of the 1-ns laser drive, a stagnating Au plasma ($\sim $ 10 mg cm$^{-3})$ forms at the center of the hohlraum. This is a consequence of supersonic, radially directed Au jets ($\sim $ 1000 $\mu $m ns$^{-1}$, $\sim $ Mach 4) formed as laser-driven plasma bubbles approach one another. Experimental details will be presented and the physics will be discussed. This work was performed at the LLE NLUF, and was supported in part by the FSC at U. of R., US DoE, LLNL, LLE, and GA. [Preview Abstract] |
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