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D T Casey - One of the best experts on this subject based on the ideXlab platform.
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measurement of hydrodynamic instability growth during the deceleration of an inertial confinement fusion Implosion
High Energy Density Physics, 2020Co-Authors: L Pickworth, B. A. Hammel, V. A. Smalyuk, D T Casey, H F Robey, C R Weber, D S Clark, A G Macphee, Le S Pape, L BerzakhopkinsAbstract:Abstract This paper presents an exploration of potential mitigation methods for the gas fuel fill tube in Inertial Confinement Fusion (ICF) Implosions at the National Ignition Facility (NIF), and the impact of hydrodynamic growth seeded from other target imperfections using a specialized low convergence Implosion experiment. Enhanced x-ray self- emission of this experiment design allows the impact of hydrodynamic growth through the deceleration phase of the Implosion to be examined. Experiments are presented comparing the perturbation visible during the Implosion deceleration that are seeded by the fill tube, through varying the initial geometry in otherwise similar Implosions. We further extend the experiment to explore the impact of isolated high atomic number 'dots' of 5 and 20 µm diameter. These isolated dots are compared in two different ‘High Density Carbon’ ablator designs in a gold hohlraum. The experiment series finds a correlation to number of high frequency self-emission features observed in deceleration and degradation in total Deuterium-Deuterium neutron yield.
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hotspot parameter scaling with velocity and yield for high adiabat layered Implosions at the national ignition facility
Physical Review E, 2020Co-Authors: K L Baker, M Hohenberger, O. L. Landen, D T Casey, B K Spears, R Nora, C A Thomas, S Khan, D T Woods, J L MilovichAbstract:This paper presents a study on hotspot parameters in indirect-drive, inertially confined fusion Implosions as they proceed through the self-heating regime. The Implosions with increasing nuclear yield reach the burning-plasma regime, hotspot ignition, and finally propagating burn and ignition. These Implosions span a wide range of alpha heating from a yield amplification of 1.7-2.5. We show that the hotspot parameters are explicitly dependent on both yield and velocity and that by fitting to both of these quantities the hotspot parameters can be fit with a single power law in velocity. The yield scaling also enables the hotspot parameters extrapolation to higher yields. This is important as various degradation mechanisms can occur on a given Implosion at fixed Implosion velocity which can have a large impact on both yield and the hotspot parameters. The yield scaling also enables the experimental dependence of the hotspot parameters on yield amplification to be determined. The Implosions reported have resulted in the highest yield (1.73×10^{16}±2.6%), yield amplification, pressure, and Implosion velocity yet reported at the National Ignition Facility.
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an analytic asymmetric piston model for the impact of mode 1 shell asymmetry on icf Implosions
Physics of Plasmas, 2020Co-Authors: O A Hurricane, O. L. Landen, D T Casey, R Nora, A L Kritcher, P K Patel, J E Field, Jim Gaffney, Kelli Humbird, Michael KruseAbstract:For many years, low mode asymmetry in inertially confined fusion (ICF) Implosions has been recognized as a potential performance limiting factor, but analysis has been limited to using simulations and searching for data correlations. Herein, an analytically solvable model based upon the simple picture of an asymmetric piston is presented. Asymmetry of the shell driving the Implosion, as opposed to asymmetry in the hot-spot, is key to the model. The model provides a unifying framework for the action of mode-1 shell asymmetry and the resulting connections between various diagnostic signatures. A key variable in the model is the shell asymmetry fraction, f, which is related to the areal density variation of the shell surrounding the hot-spot. It is shown that f is simply related to the observed hot-spot mode-1 velocity and to the concept of residual energy in an Implosion. The model presented in this paper yields explicit expressions for the hot-spot diameter, stagnation pressure, hot-spot energy, inertial confinement-time, Lawson parameter, hot-spot temperature, and fusion yield under the action of mode-1 asymmetry. Agreement is found between the theory scalings when compared to ICF Implosion data from the National Ignition Facility and to large ensembles of detailed simulations, making the theory a useful tool for interpreting data. The theory provides a basis for setting tolerable limits on asymmetry.
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density determination of the thermonuclear fuel region in inertial confinement fusion Implosions
Journal of Applied Physics, 2020Co-Authors: Pl Volegov, D T Casey, S H Batha, Cr Danly, Fe Merrill, Ch Wilde, Dc Wilson, Verena Geppertkleinrath, D N Fittinghoff, Bd AppelbeAbstract:Understanding of the thermonuclear burn in an inertial confinement fusion Implosion requires knowledge of the local deuterium–tritium (DT) fuel density. Neutron imaging of the core now provides this previously unavailable information. Two types of neutron images are required. The first is an image of the primary 14-MeV neutrons produced by the D + T fusion reaction. The second is an image of the 14-MeV neutrons that leave the Implosion hot spot and are downscattered to lower energy by elastic and inelastic collisions in the fuel. These neutrons are measured by gating the detector to record the 6–12 MeV neutrons. Using the reconstructed primary image as a nonuniform source, a set of linear equations is derived that describes the contribution of each voxel of the DT fuel region to a pixel in the downscattered image. Using the measured intensity of the 14-MeV neutrons and downscattered images, the set of equations is solved for the density distribution in the fuel region. The method is validated against test problems and simulations of high-yield Implosions. The calculated DT density distribution from one experiment is presented.Understanding of the thermonuclear burn in an inertial confinement fusion Implosion requires knowledge of the local deuterium–tritium (DT) fuel density. Neutron imaging of the core now provides this previously unavailable information. Two types of neutron images are required. The first is an image of the primary 14-MeV neutrons produced by the D + T fusion reaction. The second is an image of the 14-MeV neutrons that leave the Implosion hot spot and are downscattered to lower energy by elastic and inelastic collisions in the fuel. These neutrons are measured by gating the detector to record the 6–12 MeV neutrons. Using the reconstructed primary image as a nonuniform source, a set of linear equations is derived that describes the contribution of each voxel of the DT fuel region to a pixel in the downscattered image. Using the measured intensity of the 14-MeV neutrons and downscattered images, the set of equat...
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Density determination of the thermonuclear fuel region in inertial confinement fusion Implosions
'AIP Publishing', 2020Co-Authors: Pl Volegov, D T Casey, S H Batha, Cr Danly, Fe Merrill, Ch Wilde, Dc Wilson, Fittinghoff D, Appelbe BAbstract:Understanding of the thermonuclear burn in an inertial confinement fusion Implosion requires knowledge of the local deuterium–tritium (DT) fuel density. Neutron imaging of the core now provides this previously unavailable information. Two types of neutron images are required. The first is an image of the primary 14-MeV neutrons produced by the D + T fusion reaction. The second is an image of the 14-MeV neutrons that leave the Implosion hot spot and are downscattered to lower energy by elastic and inelastic collisions in the fuel. These neutrons are measured by gating the detector to record the 6–12 MeV neutrons. Using the reconstructed primary image as a nonuniform source, a set of linear equations is derived that describes the contribution of each voxel of the DT fuel region to a pixel in the downscattered image. Using the measured intensity of the 14-MeV neutrons and downscattered images, the set of equations is solved for the density distribution in the fuel region. The method is validated against test problems and simulations of high-yield Implosions. The calculated DT density distribution from one experiment is presented
V. N. Goncharov - One of the best experts on this subject based on the ideXlab platform.
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core conditions for alpha heating attained in direct drive inertial confinement fusion
Physical Review E, 2016Co-Authors: A Bose, S P Regan, V. N. Goncharov, R Betti, A R Christopherson, R Nora, E M Campbell, D Mangino, R L Mccrory, T. C. SangsterAbstract:It is shown that direct-drive Implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the Implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade Implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA Implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF Implosions.
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core conditions for alpha heating attained in direct drive inertial confinement fusion
Physical Review E, 2016Co-Authors: A Bose, S P Regan, R Betti, K. M. Woo, A R Christopherson, R Nora, E M Campbell, D Mangino, R L Mccrory, V. N. GoncharovAbstract:It is shown that direct-drive Implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the Implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade Implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA Implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)10.1103/PhysRevLett.117.025001] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF Implosions.
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three dimensional modeling of direct drive cryogenic Implosions on omega
Physics of Plasmas, 2016Co-Authors: I V Igumenshchev, Yu V Glebov, F. J. Marshall, V. N. Goncharov, E M Campbell, R L Mccrory, J P Knauer, D H Froula, C Forrest, S P ReganAbstract:The effects of large-scale (with Legendre modes ≲10) laser-imposed nonuniformities in direct-drive cryogenic Implosions on the OMEGA Laser System are investigated using three-dimensional hydrodynamic simulations performed using the newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (∼10–20 μm), and imperfect pointing, power balance, and timing of the beams (with typical σrms∼10 μm, 10%, and 5 ps, respectively). Two Implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which an 874-μm-diameter capsule is illuminated by about the same-diameter beams, and a more hydrodynamically efficient “R75” design using a 900-μm-diameter capsule and beams of 75% of this diameter. Simulations show that nonuniformities caused by capsule offsets and beam imbalance have the largest effect on Implosion performance. These nonuniformities lead to significant distortions of Implosion cores, resulting ...
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demonstrating ignition hydrodynamic equivalence in direct drive cryogenic Implosions on omega
Journal of Physics: Conference Series, 2016Co-Authors: V. N. Goncharov, Ronald M Epstein, S P Regan, J. A. Delettrez, R Betti, T. C. Sangster, T R Boehly, D H Edgell, E M Campbell, C J ForrestAbstract:Achieving ignition in a direct-drive cryogenic Implosion at the National Ignition Facility (NIF) requires reaching central stagnation pressures in excess of 100 Gbar, which is a factor of 3 to 4 less than what is required for indirect-drive designs. The OMEGA Laser System is used to study the physics of cryogenic Implosions that are hydrodynamically equivalent to the spherical ignition designs of the NIF. Current cryogenic Implosions on OMEGA have reached 56 Gbar, and Implosions with shell convergence CR 3.5 proceed close to 1-D predictions. Demonstrating hydrodynamic equivalence on OMEGA will require reducing coupling losses caused by cross-beam energy transfer (CBET), minimizing long- wavelength nonuniformity seeded by power imbalance and target offset, and removing target debris occumulated during cryogenic target production.
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first principles equation of state of polystyrene and its effect on inertial confinement fusion Implosions
Physical Review E, 2015Co-Authors: L A Collins, V. N. Goncharov, R L Mccrory, J D Kress, S SkupskyAbstract:Obtaining an accurate equation of state (EOS) of polystyrene (CH) is crucial to reliably design inertial confinement fusion (ICF) capsules using CH/CH-based ablators. With first-principles calculations, we have investigated the extended EOS of CH over a wide range of plasma conditions (ρ=0.1to100g/cm(3) and T=1000 to 4,000,000 K). When compared with the widely used SESAME-EOS table, the first-principles equation of state (FPEOS) of CH has shown significant differences in the low-temperature regime, in which strong coupling and electron degeneracy play an essential role in determining plasma properties. Hydrodynamic simulations of cryogenic target Implosions on OMEGA using the FPEOS table of CH have predicted ∼30% decrease in neutron yield in comparison with the usual SESAME simulations. This is attributed to the ∼5% reduction in Implosion velocity that is caused by the ∼10% lower mass ablation rate of CH predicted by FPEOS. Simulations using CH-FPEOS show better agreement with measurements of Hugoniot temperature and scattered light from ICF Implosions.
S P Regan - One of the best experts on this subject based on the ideXlab platform.
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first observation of cross beam energy transfer mitigation for direct drive inertial confinement fusion Implosions using wavelength detuning at the national ignition facility
Physical Review Letters, 2018Co-Authors: J.a. Marozas, F. J. Marshall, M J Rosenberg, M Hohenberger, T J B Collins, P B Radha, D Turnbull, P W Mckenty, J D Zuegel, S P ReganAbstract:Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and Implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement Implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 A UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.
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first observation of cross beam energy transfer mitigation for direct drive inertial confinement fusion Implosions using wavelength detuning at the national ignition facility
Physical Review Letters, 2018Co-Authors: J.a. Marozas, F. J. Marshall, M J Rosenberg, M Hohenberger, T J B Collins, P B Radha, D Turnbull, P W Mckenty, J D Zuegel, S P ReganAbstract:Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and Implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement Implosions at the National Ignition Facility by detuning the laser-source wavelengths ($\ifmmode\pm\else\textpm\fi{}2.3\text{ }\text{ }\AA{}$ UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.
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measurement of hydrodynamic growth near peak velocity in an inertial confinement fusion capsule Implosion using a self radiography technique
Physical Review Letters, 2016Co-Authors: L Pickworth, S P Regan, O. L. Landen, B. A. Hammel, V. A. Smalyuk, H F Robey, A G Macphee, M A Barrios, H A Scott, M B SchneiderAbstract:First measurements of hydrodynamic growth near peak Implosion velocity in an inertial confinement fusion (ICF) Implosion at the National Ignition Facility were obtained using a self-radiographing technique and a preimposed Legendre mode 40, λ=140 μm, sinusoidal perturbation. These are the first measurements of the total growth at the most unstable mode from acceleration Rayleigh-Taylor achieved in any ICF experiment to date, showing growth of the areal density perturbation of ∼7000×. Measurements were made at convergences of ∼5 to ∼10× at both the waist and pole of the capsule, demonstrating simultaneous measurements of the growth factors from both lines of sight. The areal density growth factors are an order of magnitude larger than prior experimental measurements and differed by ∼2× between the waist and the pole, showing asymmetry in the measured growth factors. These new measurements significantly advance our ability to diagnose perturbations detrimental to ICF Implosions, uniquely intersecting the change from an accelerating to decelerating shell, with multiple simultaneous angular views.
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core conditions for alpha heating attained in direct drive inertial confinement fusion
Physical Review E, 2016Co-Authors: A Bose, S P Regan, V. N. Goncharov, R Betti, A R Christopherson, R Nora, E M Campbell, D Mangino, R L Mccrory, T. C. SangsterAbstract:It is shown that direct-drive Implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the Implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade Implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA Implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF Implosions.
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core conditions for alpha heating attained in direct drive inertial confinement fusion
Physical Review E, 2016Co-Authors: A Bose, S P Regan, R Betti, K. M. Woo, A R Christopherson, R Nora, E M Campbell, D Mangino, R L Mccrory, V. N. GoncharovAbstract:It is shown that direct-drive Implosions on the OMEGA laser have achieved core conditions that would lead to significant alpha heating at incident energies available on the National Ignition Facility (NIF) scale. The extrapolation of the experimental results from OMEGA to NIF energy assumes only that the Implosion hydrodynamic efficiency is unchanged at higher energies. This approach is independent of the uncertainties in the physical mechanism that degrade Implosions on OMEGA, and relies solely on a volumetric scaling of the experimentally observed core conditions. It is estimated that the current best-performing OMEGA Implosion [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)10.1103/PhysRevLett.117.025001] extrapolated to a 1.9 MJ laser driver with the same illumination configuration and laser-target coupling would produce 125 kJ of fusion energy with similar levels of alpha heating observed in current highest performing indirect-drive NIF Implosions.
H F Robey - One of the best experts on this subject based on the ideXlab platform.
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measurement of hydrodynamic instability growth during the deceleration of an inertial confinement fusion Implosion
High Energy Density Physics, 2020Co-Authors: L Pickworth, B. A. Hammel, V. A. Smalyuk, D T Casey, H F Robey, C R Weber, D S Clark, A G Macphee, Le S Pape, L BerzakhopkinsAbstract:Abstract This paper presents an exploration of potential mitigation methods for the gas fuel fill tube in Inertial Confinement Fusion (ICF) Implosions at the National Ignition Facility (NIF), and the impact of hydrodynamic growth seeded from other target imperfections using a specialized low convergence Implosion experiment. Enhanced x-ray self- emission of this experiment design allows the impact of hydrodynamic growth through the deceleration phase of the Implosion to be examined. Experiments are presented comparing the perturbation visible during the Implosion deceleration that are seeded by the fill tube, through varying the initial geometry in otherwise similar Implosions. We further extend the experiment to explore the impact of isolated high atomic number 'dots' of 5 and 20 µm diameter. These isolated dots are compared in two different ‘High Density Carbon’ ablator designs in a gold hohlraum. The experiment series finds a correlation to number of high frequency self-emission features observed in deceleration and degradation in total Deuterium-Deuterium neutron yield.
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hydro instability growth of perturbation seeds from alternate capsule support strategies in indirect drive Implosions on national ignition facility
Physics of Plasmas, 2017Co-Authors: D Martinez, V. A. Smalyuk, D T Casey, J L Milovich, H F Robey, C R Weber, D S Clark, A G Macphee, K C Chen, J CrippenAbstract:Hydrodynamic instability growth of the capsule support membranes (or “tents”) and fill tubes has been studied in spherical, glow discharge polymer plastic capsule Implosions at the National Ignition Facility (NIF) [Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. In NIF Implosions, the capsules are supported by tents because the nominal 10-μm thick fill tubes are not strong enough to support capsules by themselves. After it was recognized that the tents had a significant impact of Implosion stability, new support methods were investigated, including thicker, 30-μm diameter fill tubes and cantilevered fill tubes, as described in this article. A new “sub-scale” version of the existing x-ray radiography platform was developed for measuring growing capsule perturbations in the acceleration phase of Implosions. It was calibrated using hydrodynamic growth measurements of pre-imposed capsule modulations with Legendre modes of 60, 90, 110, and 140 at convergence ratios up to ∼2.4. Subsequent experiments with 3-D ...
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mitigating the impact of hohlraum asymmetries in national ignition facility Implosions using capsule shims
Bulletin of the American Physical Society, 2016Co-Authors: Daniel Clark, V. A. Smalyuk, J L Milovich, Andrea Kritcher, H F Robey, C R Weber, Jay D. SalmonsonAbstract:Current indirect drive Implosion experiments on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] are believed to be strongly impacted by long wavelength perturbations driven by asymmetries in the hohlraum x-ray flux. To address this perturbation source, active efforts are underway to develop modified hohlraum designs with reduced asymmetry imprint. An alternative strategy, however, is to modify the capsule design to be more resilient to a given amount of hohlraum asymmetry. In particular, the capsule may be deliberately misshaped, or “shimmed,” so as to counteract the expected asymmetries from the hohlraum. Here, the efficacy of capsule shimming to correct the asymmetries in two recent NIF Implosion experiments is assessed using two-dimensional radiation hydrodynamics simulations. Despite the highly time-dependent character of the asymmetries and the high convergence ratios of these Implosions, simulations suggest that shims could be highly effective at counteracting current asymmetries and result in factors of a few enhancements in neutron yields. For higher compression designs, the yield improvement could be even greater.
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experimental results of radiation driven layered deuterium tritium Implosions with adiabat shaped drives at the national ignition facility
Physics of Plasmas, 2016Co-Authors: V. A. Smalyuk, D T Casey, J L Milovich, T Doppner, H F Robey, D S Clark, O S Jones, B Bachmann, J L Peterson, K L BakerAbstract:Radiation-driven, layered deuterium-tritium (DT) Implosions were carried out using 3-shock and 4-shock “adiabat-shaped” drives and plastic ablators on the National Ignition Facility (NIF) [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. The purpose of these shots was to gain further understanding on the relative performance of the low-foot Implosions of the National Ignition Campaign [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] versus the subsequent high-foot Implosions [T. Doppner et al., Phys. Rev. Lett. 115, 055001 (2015)]. The neutron yield performance in the experiment with the 4-shock adiabat-shaped drive was improved by factors ∼3 to ∼10, compared to five companion low-foot shots despite large low-mode asymmetries of DT fuel, while measured compression was similar to its low-foot companions. This indicated that the dominant degradation source for low-foot Implosions was ablation-front instability growth, since adiabat shaping significantly stabilized this growth. For the experiment with the low-power 3-shock adiabat-shaped drive, the DT fuel compression was significantly increased, by ∼25% to ∼36%, compared to its companion high-foot Implosions. The neutron yield increased by ∼20%, lower than the increase of ∼50% estimated from one-dimensional scaling, suggesting the importance of residual instabilities and asymmetries. For the experiment with the high-power, 3-shock adiabat-shaped drive, the DT fuel compression was slightly increased by ∼14% compared to its companion high-foot experiments. However, the compression was reduced compared to the lower-power 3-shock adiabat-shaped drive, correlated with the increase of hot electrons that hypothetically can be responsible for reduced compression in high-power adiabat-shaped experiments as well as in high-foot experiments. The total neutron yield in the high-power 3-shock adiabat-shaped shot N150416 was 8.5 × 1015 ± 0.2 × 1015, with the fuel areal density of 0.90 ± 0.07 g/cm2, corresponding to the ignition threshold factor parameter IFTX (calculated without alpha heating) of 0.34 ± 0.03 and the yield amplification due to the alpha heating of 2.4 ± 0.2. The performance parameters were among the highest of all shots on NIF and the closest to ignition at this time, based on the IFTX metric. The follow-up experiments were proposed to continue testing physics hypotheses, to measure Implosion reproducibility, and to improve quantitative understanding on present Implosion results.
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measurement of hydrodynamic growth near peak velocity in an inertial confinement fusion capsule Implosion using a self radiography technique
Physical Review Letters, 2016Co-Authors: L Pickworth, S P Regan, O. L. Landen, B. A. Hammel, V. A. Smalyuk, H F Robey, A G Macphee, M A Barrios, H A Scott, M B SchneiderAbstract:First measurements of hydrodynamic growth near peak Implosion velocity in an inertial confinement fusion (ICF) Implosion at the National Ignition Facility were obtained using a self-radiographing technique and a preimposed Legendre mode 40, λ=140 μm, sinusoidal perturbation. These are the first measurements of the total growth at the most unstable mode from acceleration Rayleigh-Taylor achieved in any ICF experiment to date, showing growth of the areal density perturbation of ∼7000×. Measurements were made at convergences of ∼5 to ∼10× at both the waist and pole of the capsule, demonstrating simultaneous measurements of the growth factors from both lines of sight. The areal density growth factors are an order of magnitude larger than prior experimental measurements and differed by ∼2× between the waist and the pole, showing asymmetry in the measured growth factors. These new measurements significantly advance our ability to diagnose perturbations detrimental to ICF Implosions, uniquely intersecting the change from an accelerating to decelerating shell, with multiple simultaneous angular views.
F. J. Marshall - One of the best experts on this subject based on the ideXlab platform.
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effect of cross beam energy transfer on target offset asymmetry in direct drive inertial confinement fusion Implosions
Physics of Plasmas, 2020Co-Authors: K S Anderson, F. J. Marshall, J.a. Marozas, C J Forrest, D T Michel, O M Mannion, R C Shah, P B Radha, D H EdgellAbstract:The unintentional mispositioning of inertial confinement fusion (ICF) capsules from the center of laser beam convergence has long been shown in simulations to generate large l = 1 asymmetry and significantly degrade Implosion symmetry and fusion yields. Experimental yields on the OMEGA laser system, however, have shown much less sensitivity to this initial target offset. This paper presents simulations of offset ICF Implosions improved by including a physics model of cross-beam energy transfer (CBET), a mechanism of laser energy scattering from one beam to another. Room-temperature OMEGA Implosion experiments with prescribed target offsets are simulated with and without CBET, illustrating that CBET mitigates the l = 1 Implosion asymmetry from the target offset. Comparison of simulations to multiple complementary experimental observables indicates that the addition of CBET physics in offset simulations is necessary to match experimental results.
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first observation of cross beam energy transfer mitigation for direct drive inertial confinement fusion Implosions using wavelength detuning at the national ignition facility
Physical Review Letters, 2018Co-Authors: J.a. Marozas, F. J. Marshall, M J Rosenberg, M Hohenberger, T J B Collins, P B Radha, D Turnbull, P W Mckenty, J D Zuegel, S P ReganAbstract:Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and Implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement Implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 A UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.
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first observation of cross beam energy transfer mitigation for direct drive inertial confinement fusion Implosions using wavelength detuning at the national ignition facility
Physical Review Letters, 2018Co-Authors: J.a. Marozas, F. J. Marshall, M J Rosenberg, M Hohenberger, T J B Collins, P B Radha, D Turnbull, P W Mckenty, J D Zuegel, S P ReganAbstract:Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and Implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement Implosions at the National Ignition Facility by detuning the laser-source wavelengths ($\ifmmode\pm\else\textpm\fi{}2.3\text{ }\text{ }\AA{}$ UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.
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three dimensional modeling of direct drive cryogenic Implosions on omega
Physics of Plasmas, 2016Co-Authors: I V Igumenshchev, Yu V Glebov, F. J. Marshall, V. N. Goncharov, E M Campbell, R L Mccrory, J P Knauer, D H Froula, C Forrest, S P ReganAbstract:The effects of large-scale (with Legendre modes ≲10) laser-imposed nonuniformities in direct-drive cryogenic Implosions on the OMEGA Laser System are investigated using three-dimensional hydrodynamic simulations performed using the newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (∼10–20 μm), and imperfect pointing, power balance, and timing of the beams (with typical σrms∼10 μm, 10%, and 5 ps, respectively). Two Implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which an 874-μm-diameter capsule is illuminated by about the same-diameter beams, and a more hydrodynamically efficient “R75” design using a 900-μm-diameter capsule and beams of 75% of this diameter. Simulations show that nonuniformities caused by capsule offsets and beam imbalance have the largest effect on Implosion performance. These nonuniformities lead to significant distortions of Implosion cores, resulting ...
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inertial confinement fusion Implosions with imposed magnetic field compression using the omega laser
Physics of Plasmas, 2012Co-Authors: M Hohenberger, F. J. Marshall, R Betti, D. D. Meyerhofer, J P Knauer, P Y Chang, F H Seguin, G Fiksel, R D PetrassoAbstract:Experiments applying laser-driven magnetic-flux compression to inertial confinement fusion (ICF) targets to enhance the Implosion performance are described. Spherical plastic (CH) targets filled with 10 atm of deuterium gas were imploded by the OMEGA Laser, compare Phys. Plasmas 18, 056703 or Phys. Plasmas 18, 056309. Before being imploded, the targets were immersed in an 80-kG magnetic seed field. Upon laser irradiation, the high Implosion velocities and ionization of the target fill trapped the magnetic field inside the capsule, and it was amplified to tens of megagauss through flux compression. At such strong magnetic fields, the hot spot inside the spherical target was strongly magnetized, reducing the heat losses through electron confinement. The experimentally observed ion temperature was enhanced by 15%, and the neutron yield was increased by 30%, compared to nonmagnetized Implosions [P. Y. Chang et al., Phys. Rev. Lett. 107, 035006 (2011)]. This represents the first experimental verification of pe...
