Nova-driven winds in globular clusters

NASA Technical Reports Server (NTRS)

Scott, E. H.; Durisen, R. H.

1978-01-01

Recent sensitive searches for H-alpha emission from ionized intracluster gas in globular clusters have set upper limits that conflict with theoretical predictions. It is suggested that nova outbursts heat the gas, producing winds that resolve this discrepancy. The incidence of novae in globular clusters, the conversion of kinetic energy of the nova shell to thermal energy of the intracluster gas, and the characteristics of the resultant winds are discussed. Calculated emission from the nova-driven models does not conflict with any observations to date. Some suggestions are made concerning the most promising approaches for future detection of intracluster gas on the basis of these models. The possible relationship of nova-driven winds to globular cluster X-ray sources is also considered.

Systematic Fuel Cavity Asymmetries in Directly Driven Inertial Confinement Fusion Implosions

DOE PAGES

Shah, Rahul C.; Haines, Brian Michael; Wysocki, Frederick Joseph; ...

2017-03-30

Here, we present narrow-band self-emission x-ray images from a titanium tracer layer placed at the fuel-shell interface in 60-laser-beam implosion experiments at the OMEGA facility. The images are acquired during deceleration with inferred convergences of ~9-14. Novel here is that a systematically observed asymmetry of the emission is linked, using full sphere 3D implosion modeling, to performance-limiting low mode asymmetry of the drive.

Zonal flow generation in inertial confinement fusion implosions

DOE PAGES

Peterson, J. L.; Humbird, K. D.; Field, J. E.; ...

2017-03-06

A supervised machine learning algorithm trained on a multi-petabyte dataset of inertial confinement fusion simulations has identified a class of implosions that robustly achieve high yield, even in the presence of drive variations and hydrodynamic perturbations. These implosions are purposefully driven with a time-varying asymmetry, such that coherent flow generation during hotspot stagnation forces the capsule to self-organize into an ovoid, a shape that appears to be more resilient to shell perturbations than spherical designs. Here this new class of implosions, whose configurations are reminiscent of zonal flows in magnetic fusion devices, may offer a path to robust inertial fusion.

Zonal flow generation in inertial confinement fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, J. L.; Humbird, K. D.; Field, J. E.

A supervised machine learning algorithm trained on a multi-petabyte dataset of inertial confinement fusion simulations has identified a class of implosions that robustly achieve high yield, even in the presence of drive variations and hydrodynamic perturbations. These implosions are purposefully driven with a time-varying asymmetry, such that coherent flow generation during hotspot stagnation forces the capsule to self-organize into an ovoid, a shape that appears to be more resilient to shell perturbations than spherical designs. Here this new class of implosions, whose configurations are reminiscent of zonal flows in magnetic fusion devices, may offer a path to robust inertial fusion.

Simulation of alternate hohlraum shapes for improved inner beam propagation in indirectly-driven ICF implosions

NASA Astrophysics Data System (ADS)

Robey, H. F.; Berzak Hopkins, L. F.

2017-10-01

Recent indirectly-driven ICF experiments performed on the National Ignition Facility have shown that the propagation of the inner beam cones is impeded late in the laser pulse by the growth of a gold bubble, which is initiated at the location where the outer beams hit the hohlraum wall and which expands radially inward into the hohlraum as the implosion progresses. Late in time, this gold bubble intercepts a significant portion of the inner beams reducing the available energy reaching the waist of the hohlraum and affecting the implosion symmetry. Integrated hohlraum simulations of alternate hohlraum shapes using HYDRA are performed to explore options for reducing the impact of the gold bubble on inner beam propagation. The simulations are based on recent NIF implosions using High-Density Carbon (HDC) ablators, which have shown good performance, but which could benefit from improved inner beam propagation. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

Multi-Fluid Interpenetration Mixing in X-ray and Directly Laser driven ICF Capsule Implosions

NASA Astrophysics Data System (ADS)

Wilson, Douglas

2003-10-01

Mix between a surrounding shell and the fuel leads to degradation in ICF capsule performance. Both indirectly (X-ray) and directly laser driven implosions provide a wealth of data to test mix models. One model, the multi-fluid interpenetration mix model of Scannapieco and Cheng (Phys. Lett. A., 299, 49, 2002), was implemented in an ICF code and applied to a wide variety of experiments (e.g. J. D. Kilkenny et al., Proc. Conf Plasm. Phys. Contr. Nuc. Fus. Res. 3, 29(1988), P. Amendt, R. E. Turner, O. L. Landen, Phy. Rev. Lett., 89, 165001 (2002), or Li et al., Phy. Rev. Lett, 89, 165002 (2002)). With its single adjustable parameter fixed, it replicates well the yield degradation with increasing convergence ratio for both directly and indirectly driven capsules. Often, but not always the ion temperatures with mixing are calculated to be higher than in an unmixed implosion, agreeing with observations. Comparison with measured directly driven implosion yield rates ( from the neutron temporal diagnostic or NTD) shows mixing increases rapidly during the burn. The model also reproduces the decrease of the fuel "rho-r" with fill gas pressure, measured by observing escaping deuterons or secondary neutrons. The mix model assumes fully atomically mixed constituents, but when experiments with deuterated plastic layers and 3He fuel are modeled, less that full atomic mix is appropriate. Applying the mix model to the ablator - solid DT interface in indirectly driven ignition capsules for the NIF or LMJ suggests that the capsules will ignite, but that burn after ignition may be somewhat degraded. Situations in which the Scannapieco and Cheng model fails to agree with experiments can guide us to improvements or the development of other models. Some directly driven symmetric implosions suggest that in highly mixed situations, a higher value of the mix parameter may needed. Others show the model underestimating the fuel burn temperature. This work was performed by the Los Alamos National Laboratory under DOE contract number W-7405-Eng-36.

Proton Radiography of Spontaneous Fields, Plasma Flows and Dynamics in X-Ray Driven Inertial-Confinement Fusion Implosions

NASA Astrophysics Data System (ADS)

Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rosenberg, M.; Zylstra, A. B.; Rinderknecht, H. G.; Petrasso, R. D.; Amendt, P. A.; Landen, O. L.; Town, R. P. J.; Betti, R.; Knauer, J. P.; Meyerhofer, D. D.; Back, C. A.; Kilkenny, J. D.; Nikroo, A.

2010-11-01

Backlighting of x-ray-driven implosions in empty hohlraums with mono-energetic protons on the OMEGA laser facility has allowed a number of important phenomena to be observed. Several critical parameters were determined, including plasma flow, three types of spontaneous electric fields and megaGauss magnetic fields. These results provide insight into important issues in indirect-drive ICF. Even though the cavity is effectively a Faraday cage, the strong, local fields inside the hohlraum can affect laser-plasma instabilities, electron distributions and implosion symmetry. They are of fundamental scientific importance for a range of new experiments at the frontiers of high-energy-density physics. Future experiments designed to characterize the field formation and evolution in low-Z gas fill hohlraums will be discussed.

Hard x-ray (>100 keV) imager to measure hot electron preheat for indirectly driven capsule implosions on the NIF.

PubMed

Döppner, T; Dewald, E L; Divol, L; Thomas, C A; Burns, S; Celliers, P M; Izumi, N; Kline, J L; LaCaille, G; McNaney, J M; Prasad, R R; Robey, H F; Glenzer, S H; Landen, O L

2012-10-01

We have fielded a hard x-ray (>100 keV) imager with high aspect ratio pinholes to measure the spatially resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions and are a source of preheat to the deuterium-tritium fuel. First measurements show that hot electron preheat does not limit obtaining the fuel areal densities required for ignition and burn.

Implosion of multilayered cylindrical targets driven by intense heavy ion beams.

PubMed

Piriz, A R; Portugues, R F; Tahir, N A; Hoffmann, D H H

2002-11-01

An analytical model for the implosion of a multilayered cylindrical target driven by an intense heavy ion beam has been developed. The target is composed of a cylinder of frozen hydrogen or deuterium, which is enclosed in a thick shell of solid lead. This target has been designed for future high-energy-density matter experiments to be carried out at the Gesellschaft für Schwerionenforschung, Darmstadt. The model describes the implosion dynamics including the motion of the incident shock and the first reflected shock and allows for calculation of the physical conditions of the hydrogen at stagnation. The model predicts that the conditions of the compressed hydrogen are not sensitive to significant variations in target and beam parameters. These predictions are confirmed by one-dimensional numerical simulations and thus allow for a robust target design.

Data driven models of the performance and repeatability of NIF high foot implosions

NASA Astrophysics Data System (ADS)

Gaffney, Jim; Casey, Dan; Callahan, Debbie; Hartouni, Ed; Ma, Tammy; Spears, Brian

2015-11-01

Recent high foot (HF) inertial confinement fusion (ICF) experiments performed at the national ignition facility (NIF) have consisted of enough laser shots that a data-driven analysis of capsule performance is feasible. In this work we use 20-30 individual implosions of similar design, spanning laser drive energies from 1.2 to 1.8 MJ, to quantify our current understanding of the behavior of HF ICF implosions. We develop a probabilistic model for the projected performance of a given implosion and use it to quantify uncertainties in predicted performance including shot-shot variations and observation uncertainties. We investigate the statistical significance of the observed performance differences between different laser pulse shapes, ablator materials, and capsule designs. Finally, using a cross-validation technique, we demonstrate that 5-10 repeated shots of a similar design are required before real trends in the data can be distinguished from shot-shot variations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-674957.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robey, H. F.; MacGowan, B. J.; Landen, O. L.

Indirectly driven capsule implosions on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] are being performed with the goal of compressing a layer of cryogenic deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain the self-propagating burn wave that is required for fusion power gain greater than unity. These implosions are driven with a temporally shaped laser pulse that is carefully tailored to keep the DT fuel on a low adiabat (ratio of fuel pressure to the Fermi degenerate pressure). In this report, the impact of variations in the laser pulse shapemore » (both intentionally and unintentionally imposed) on the in-flight implosion adiabat is examined by comparing the measured shot-to-shot variations in ρR from a large ensemble of DT-layered ignition target implosions on NIF spanning a two-year period. A strong sensitivity to variations in the early-time, low-power foot of the laser pulse is observed. It is shown that very small deviations (∼0.1% of the total pulse energy) in the first 2 ns of the laser pulse can decrease the measured ρR by 50%.« less

Diagnosing radiative shocks from deuterium and tritium implosions on NIF.

PubMed

Pak, A; Divol, L; Weber, S; Döppner, T; Kyrala, G A; Kilne, J; Izumi, N; Glenn, S; Ma, T; Town, R P; Bradley, D K; Glenzer, S H

2012-10-01

During the recent ignition tuning campaign at the National Ignition Facility, layered cryogenic deuterium and tritium capsules were imploded via x-ray driven ablation. The hardened gated x-ray imager diagnostic temporally and spatially resolves the x-ray emission from the core of the capsule implosion at energies above ~8 keV. On multiple implosions, ~200-400 ps after peak compression a spherically expanding radiative shock has been observed. This paper describes the methods used to characterize the radial profile and rate of expansion of the shock induced x-ray emission.

A near one-dimensional indirectly driven implosion at convergence ratio 30

NASA Astrophysics Data System (ADS)

MacLaren, S. A.; Masse, L. P.; Czajka, C. E.; Khan, S. F.; Kyrala, G. A.; Ma, T.; Ralph, J. E.; Salmonson, J. D.; Bachmann, B.; Benedetti, L. R.; Bhandarkar, S. D.; Bradley, P. A.; Hatarik, R.; Herrmann, H. W.; Mariscal, D. A.; Millot, M.; Patel, P. K.; Pino, J. E.; Ratledge, M.; Rice, N. G.; Tipton, R. E.; Tommasini, R.; Yeamans, C. B.

2018-05-01

Inertial confinement fusion cryogenic-layered implosions at the National Ignition Facility, while successfully demonstrating self-heating due to alpha-particle deposition, have fallen short of the performance predicted by one-dimensional (1D) multi-physics implosion simulations. The current understanding, from experimental evidence as well as simulations, suggests that engineering features such as the capsule tent and fill tube, as well as time-dependent low-mode asymmetry, are to blame for the lack of agreement. A short series of experiments designed specifically to avoid these degradations to the implosion are described here in order to understand if, once they are removed, a high-convergence cryogenic-layered deuterium-tritium implosion can achieve the 1D simulated performance. The result is a cryogenic layered implosion, round at stagnation, that matches closely the performance predicted by 1D simulations. This agreement can then be exploited to examine the sensitivity of approximations in the model to the constraints imposed by the data.

Progress of LMJ-relevant implosions experiments on OMEGA

NASA Astrophysics Data System (ADS)

Casner, A.; Philippe, F.; Tassin, V.; Seytor, P.; Monteil, M.-C.; Gauthier, P.; Park, H. S.; Robey, H.; Ross, J.; Amendt, P.; Girard, F.; Villette, B.; Reverdin, C.; Loiseau, P.; Caillaud, T.; Landoas, O.; Li, C. K.; Petrasso, R.; Seguin, F.; Rosenberg, M.; Renaudin, P.

2013-11-01

In preparation of the first ignition attempts on the Laser Mégajoule (LMJ), an experimental program is being pursued on OMEGA to investigate LMJ-relevant hohlraums. First, radiation temperature levels close to 300 eV were recently achieved in reduced-scale hohlraums with modest backscatter losses. Regarding the baseline target design for fusion experiments on LMJ, an extensive experimental database has also been collected for scaled implosions experiments in both empty and gas-filled rugby-shaped hohlraums. We acquired a full picture of hohlraum energetics and implosion dynamics. Not only did the rugby hohlraums show significantly higher x-ray drive energy over the cylindrical hohlraums, but symmetry control by power balance was demonstrated, as well as high-performance D2 implosions enabling the use of a complete suite of neutrons diagnostics. Charged particle diagnostics provide complementary insights into the physics of these x-ray driven implosions. An overview of these results demonstrates our ability to control the key parameters driving the implosion, lending more confidence in extrapolations to ignition-scale targets.

The I-Raum: A new shaped hohlraum for improved inner beam propagation in indirectly-driven ICF implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Robey, H. F.; Berzak Hopkins, L.; Milovich, J. L.; Meezan, N. B.

2018-01-01

Recent work in indirectly-driven inertial confinement fusion implosions on the National Ignition Facility has indicated that late-time propagation of the inner cones of laser beams (23° and 30°) is impeded by the growth of a "bubble" of hohlraum wall material (Au or depleted uranium), which is initiated by and is located at the location where the higher-intensity outer beams (44° and 50°) hit the hohlraum wall. The absorption of the inner cone beams by this "bubble" reduces the laser energy reaching the hohlraum equator at late time driving an oblate or pancaked implosion, which limits implosion performance. In this article, we present the design of a new shaped hohlraum designed specifically to reduce the impact of this bubble by adding a recessed pocket at the location where the outer cones hit the hohlraum wall. This recessed pocket displaces the bubble radially outward, reducing the inward penetration of the bubble at all times throughout the implosion and increasing the time for inner beam propagation by approximately 1 ns. This increased laser propagation time allows one to drive a larger capsule, which absorbs more energy and is predicted to improve implosion performance. The new design is based on a recent National Ignition Facility shot, N170601, which produced a record neutron yield. The expansion rate and absorption of laser energy by the bubble is quantified for both cylindrical and shaped hohlraums, and the predicted performance is compared.

Hybrid strategy for increasing fusion performance and stagnation pressure in x-ray driven inertially confined fusion implosions on the NIF

NASA Astrophysics Data System (ADS)

Hurricane, O. A.; Callahan, D. A.; Edwards, M. J.; Casey, D.; Doeppner, T.; Hohenberger, M.; Hinkel, D.; Berzak Hopkins, L.; Le Pape, S.; MacLaren, S.; Masse, L.; Thomas, C.; Zylstra, A.

2017-10-01

Post NIC (2012), more stable and lower convergence implosions were developed and used as part of a `basecamp' strategy to identify obstacles to further performance. From 2013-2015 by probing away from a conservative working implosion in-steps towards conditions of higher velocity and compression, `Fuel Gain' and alpha-heating were obtained. In the process, performance cliffs unrelated to `mix' were identified the most impactful of which were symmetry control of the implosion and hydro seeded by engineering features. From 2015-2017 we focused on mitigating poor symmetry control and engineering improvements on fill-tubes and capsule mounting techniques. The results were more efficient implosions that can obtain the same performance levels as the earlier implosions, but with less laser energy. Presently, the best of these implosions is poised to step into a burning plasma state. Here, we describe the next step in our strategy that involves using the data we've acquired across parameter space to make a step to the largest symmetric implosions that can be fielded on NIF with the energy available. We describe the key principles that form the foundation of this approach. Performed under the auspices of U.S. Dept. of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Berzak Hopkins, L. F.; Ma, T.; Ralph, J. E.; Albert, F.; Benedetti, L. R.; Celliers, P. M.; Döppner, T.; Goyon, C. S.; Izumi, N.; Jarrott, L. C.; Khan, S. F.; Kline, J. L.; Kritcher, A. L.; Kyrala, G. A.; Nagel, S. R.; Pak, A. E.; Patel, P.; Rosen, M. D.; Rygg, J. R.; Schneider, M. B.; Turnbull, D. P.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

2016-11-01

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4 ×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robey, H. F.; Smalyuk, V. A.; Milovich, J. L.

A series of indirectly driven capsule implosions has been performed on the National Ignition Facility to assess the relative contributions of ablation-front instability growth vs. fuel compression on implosion performance. Laser pulse shapes for both low and high-foot pulses were modified to vary ablation-front growth and fuel adiabat, separately and controllably. Three principal conclusions are drawn from this study: (1) It is shown that reducing ablation-front instability growth in low-foot implosions results in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. (2) It is shown that reducing the fuel adiabat in high-foot implosions results inmore » a significant (36%) increase in fuel compression together with a small (10%) increase in neutron yield. (3) Increased electron preheat at higher laser power in high-foot implosions, however, appears to offset the gain in compression achieved by adiabat-shaping at lower power. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results.« less

Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility.

PubMed

Hinkel, D E; Berzak Hopkins, L F; Ma, T; Ralph, J E; Albert, F; Benedetti, L R; Celliers, P M; Döppner, T; Goyon, C S; Izumi, N; Jarrott, L C; Khan, S F; Kline, J L; Kritcher, A L; Kyrala, G A; Nagel, S R; Pak, A E; Patel, P; Rosen, M D; Rygg, J R; Schneider, M B; Turnbull, D P; Yeamans, C B; Callahan, D A; Hurricane, O A

2016-11-25

Analyses of high foot implosions show that performance is limited by the radiation drive environment, i.e., the hohlraum. Reported here are significant improvements in the radiation environment, which result in an enhancement in implosion performance. Using a longer, larger case-to-capsule ratio hohlraum at lower gas fill density improves the symmetry control of a high foot implosion. Moreover, for the first time, these hohlraums produce reduced levels of hot electrons, generated by laser-plasma interactions, which are at levels comparable to near-vacuum hohlraums, and well within specifications. Further, there is a noteworthy increase in laser energy coupling to the hohlraum, and discrepancies with simulated radiation production are markedly reduced. At fixed laser energy, high foot implosions driven with this improved hohlraum have achieved a 1.4×increase in stagnation pressure, with an accompanying relative increase in fusion yield of 50% as compared to a reference experiment with the same laser energy.

On the importance of minimizing "coast-time" in x-ray driven inertially confined fusion implosions

NASA Astrophysics Data System (ADS)

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.; Landen, O.; Patel, P. K.; Springer, P. T.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Hinkel, D. E.; Berzak Hopkins, L. F.; Kline, J.; Le Pape, S.; Ma, T.; MacPhee, A. G.; Moore, A.; Pak, A.; Park, H.-S.; Ralph, J.; Salmonson, J. D.; Widmann, K.

2017-09-01

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400 × , making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, toff, well before bang-time, tBT, for a coast-time of t coast = t B T - t o f f > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnation pressure and fusion yield. Herein we show that the ablation pressure, pabl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing tcoast boosts pabl by as much as ˜ 2 × prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after toff to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ˜ 15 % higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small ( ˜ 5 % - 10 %) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ˜ 2 × as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Finally, we show how the high-foot implosion data is consistent with the above mentioned picture.

On the importance of minimizing “coast-time” in x-ray driven inertially confined fusion implosions

DOE PAGES

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.; ...

2017-09-01

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400×, making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, t off, well before bang-time, t BT, for a coast-time of t coast = t BT – t off > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnationmore » pressure and fusion yield. Herein we show that the ablation pressure, p abl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing t coast boosts p abl by as much as ~2× prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after t off to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ~15% higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small (~5%–10%) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ~2× as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Lastly, we show how the high-foot implosion data is consistent with the above mentioned picture.« less

On the importance of minimizing “coast-time” in x-ray driven inertially confined fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A.; Kritcher, A.; Callahan, D. A.

By the time an inertially confined fusion (ICF) implosion has converged a factor of 20, its surface area has shrunk 400×, making it an inefficient x-ray energy absorber. So, ICF implosions are traditionally designed to have the laser drive shut off at a time, t off, well before bang-time, t BT, for a coast-time of t coast = t BT – t off > 1 ns. High-foot implosions on NIF showed a strong dependence of many key ICF performance quantities on reduced coast-time (by extending the duration of laser power after the peak power is first reached), most notably stagnationmore » pressure and fusion yield. Herein we show that the ablation pressure, p abl, which drives high-foot implosions, is essentially triangular in temporal shape, and that reducing t coast boosts p abl by as much as ~2× prior to stagnation thus increasing fuel and hot-spot compression and implosion speed. One-dimensional simulations are used to track hydrodynamic characteristics for implosions with various coast-times and various assumed rates of hohlraum cooling after t off to illustrate how the late-time conditions exterior to the implosion can impact the fusion performance. A simple rocket model-like analytic theory demonstrates that reducing coast-time can lead to a ~15% higher implosion velocity because the reduction in x-ray absorption efficiency at late-time is somewhat compensated by small (~5%–10%) ablator mass remaining. Together with the increased ablation pressure, the additional implosion speed for short coast-time implosions can boost the stagnation pressure by ~2× as compared to a longer coast-time version of the same implosion. Four key dimensionless parameters are identified and we find that reducing coast-time to as little as 500 ps still provides some benefit. Lastly, we show how the high-foot implosion data is consistent with the above mentioned picture.« less

Polar-Direct-Drive Defect Implosions at OMEGA inPreparation for Experiments at NIF

NASA Astrophysics Data System (ADS)

Cobble, J. A.; Schmitt, M. J.; Murphy, T. J.; Tregillis, I. L.; Wysocki, F. J.; Obrey, K. D.; Magelssen, G. R.; Glebov, V.; Bradley, P. A.; Hsu, S. C.; Krasheninnikova, N. V.; Batha, S. H.

2011-10-01

The Defect-Implosion (DIME) campaign involves compressing perturbed spherical capsules with polar direct drive (PDD). For direct-drive implosions at NIF, PDD will be used. We have done simulations and experiments at OMEGA to test our modeling capability for equatorial-plane defects in fusion capsules and for PDD at NIF. Since PDD is anisotropic, we show the results of 0th hydrodynamics of implosions and perturbation-driven features near stagnation. Later presentations discuss defect-induced mix and neutronics, and laser pointing for NIF experiments. Prototype OMEGA shots used 865- μm diameter CH shells filled with 5 atm of D2. Machined channels 30- μm wide and up to 9- μm deep formed the defects. This work has been performed under the auspices of the US DOE, contract number DE-AC52-06NA25396.

Precision shock tuning on the national ignition facility.

PubMed

Robey, H F; Celliers, P M; Kline, J L; Mackinnon, A J; Boehly, T R; Landen, O L; Eggert, J H; Hicks, D; Le Pape, S; Farley, D R; Bowers, M W; Krauter, K G; Munro, D H; Jones, O S; Milovich, J L; Clark, D; Spears, B K; Town, R P J; Haan, S W; Dixit, S; Schneider, M B; Dewald, E L; Widmann, K; Moody, J D; Döppner, T D; Radousky, H B; Nikroo, A; Kroll, J J; Hamza, A V; Horner, J B; Bhandarkar, S D; Dzenitis, E; Alger, E; Giraldez, E; Castro, C; Moreno, K; Haynam, C; LaFortune, K N; Widmayer, C; Shaw, M; Jancaitis, K; Parham, T; Holunga, D M; Walters, C F; Haid, B; Malsbury, T; Trummer, D; Coffee, K R; Burr, B; Berzins, L V; Choate, C; Brereton, S J; Azevedo, S; Chandrasekaran, H; Glenzer, S; Caggiano, J A; Knauer, J P; Frenje, J A; Casey, D T; Johnson, M Gatu; Séguin, F H; Young, B K; Edwards, M J; Van Wonterghem, B M; Kilkenny, J; MacGowan, B J; Atherton, J; Lindl, J D; Meyerhofer, D D; Moses, E

2012-05-25

Ignition implosions on the National Ignition Facility [J. D. Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with the goal of compressing deuterium-tritium fuel to a sufficiently high areal density (ρR) to sustain a self-propagating burn wave required for fusion power gain greater than unity. These implosions are driven with a very carefully tailored sequence of four shock waves that must be timed to very high precision to keep the fuel entropy and adiabat low and ρR high. The first series of precision tuning experiments on the National Ignition Facility, which use optical diagnostics to directly measure the strength and timing of all four shocks inside a hohlraum-driven, cryogenic liquid-deuterium-filled capsule interior have now been performed. The results of these experiments are presented demonstrating a significant decrease in adiabat over previously untuned implosions. The impact of the improved shock timing is confirmed in related deuterium-tritium layered capsule implosions, which show the highest fuel compression (ρR~1.0 g/cm(2)) measured to date, exceeding the previous record [V. Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)] by more than a factor of 3. The experiments also clearly reveal an issue with the 4th shock velocity, which is observed to be 20% slower than predictions from numerical simulation.

Calibration of Hydrophone Stations: Lessons Learned from the Ascension Island Experiment

DTIC Science & Technology

2000-09-01

source based on the implosion of a glass sphere for future long-range calibrations. RESEARCH ACCOMPLISHED The J.C. Ross, an icebreaker class...waters around Ascension Island. The blow - ups show the track in the immediate vicinity of the three hydrophones and plots their nominal location. The...used has practical and cost-driven limitations. Small implosive sources such as lightbulbs have been used from ships as hydrophone calibration sources

Preconditioned wire array Z-pinches driven by a double pulse current generator

NASA Astrophysics Data System (ADS)

Wu, Jian; Lu, Yihan; Sun, Fengju; Li, Xingwen; Jiang, Xiaofeng; Wang, Zhiguo; Zhang, Daoyuan; Qiu, Aici; Lebedev, Sergey

2018-07-01

Suppression of the core-corona structure and wire ablation in wire array Z-pinches is investigated using a novel double pulse current generator ‘Qin-1’ facility. The ‘Qin-1’ facility allows coupling a ∼10 kA 20 ns prepulse generator with a ∼0.8 MA 160 ns main current generator. The tailored prepulse current preheats wires to a gaseous state and the time interval between the prepulse and the main current pulse allows formation of a more uniform mass distribution for the implosion. The implosion of a gasified two aluminum-wire array showed no ablation phase and allowed all array mass to participate in the implosion. The initial perturbations formed from the inhomogeneous ablation were suppressed, however, the magneto Rayleigh–Taylor (MRT) instability during the implosion was still significant and further researches on the generation and development of the MRT instabilities of this gasified wire array are needed.

Exploration of kinetic and multiple-ion-fluids effects in D3He and T3He gas-filled ICF implosions using multiple nuclear reaction histories

NASA Astrophysics Data System (ADS)

Sio, Hong; Rinderknecht, Hans; Rosenberg, Michael; Zylstra, Alex; Séguin, Fredrick; Gatu Johnson, Maria; Li, Chikang; Petrasso, Richard; Hoffman, Nelson; Kagan, Krigory; Molvig, Kim; Amendt, Peter; Bellei, Claudio; Wilks, Scott; Stoeckl, Christian; Glebov, Vladimir; Betti, Riccardo; Sangster, Thomas; Katz, Joseph

2014-10-01

To explore kinetic and multi-ion-fluid effects in D3He and T3He gas-filled shock-driven implosions, multiple nuclear reaction histories were measured using the upgraded Particle Temporal Diagnostic (PTD) on OMEGA. For D3He gas-filled implosions, the relative timing of the DD and D3He reaction histories were measured with 20 ps precision. For T3He gas-filled implosions (with 1-2% deuterium), the relative timing of the DT and D3He reaction histories were measured with 10 ps precision. The observed differences between the reaction histories on these two OMEGA experiments are contrasted to 1-D single-ion hydro simulations for different gas-fill pressure and gas mixture. This work is supported in part by the U.S. DOE, LLNL, LLE, and NNSA SSGF.

Ion temperature measurements of indirect-drive implosions with the neutron time-of-flight detector on SG-III laser facility

NASA Astrophysics Data System (ADS)

Chen, Zhongjing; Zhang, Xing; Pu, Yudong; Yan, Ji; Huang, Tianxuan; Jiang, Wei; Yu, Bo; Chen, Bolun; Tang, Qi; Song, Zifeng; Chen, Jiabin; Zhan, Xiayu; Liu, Zhongjie; Xie, Xufei; Jiang, Shaoen; Liu, Shenye

2018-02-01

The accuracy of the determination of the burn-averaged ion temperature of inertial confinement fusion implosions depends on the unfold process, including deconvolution and convolution methods, and the function, i.e., the detector response, used to fit the signals measured by neutron time-of-flight (nToF) detectors. The function given by Murphy et al. [Rev. Sci. Instrum. 68(1), 610-613 (1997)] has been widely used in Nova, Omega, and NIF. There are two components, i.e., fast and slow, and the contribution of scattered neutrons has not been dedicatedly considered. In this work, a new function, based on Murphy's function has been employed to unfold nToF signals. The contribution of scattered neutrons is easily included by the convolution of a Gaussian response function and an exponential decay. The ion temperature is measured by nToF with the new function. Good agreement with the ion temperature determined by the deconvolution method has been achieved.

Comparison and analysis of the results of direct-driven targets implosion

NASA Astrophysics Data System (ADS)

Demchenko, N. N.; Dolgoleva, G. V.; Gus'kov, S. Yu; Kuchugov, P. A.; Rozanov, V. B.; Stepanov, R. V.; Zmitrenko, N. V.; Yakhin, R. A.

2017-10-01

The article presents calculation results, which were received for the implosion of the typical cryogenic thermonuclear direct-drive targets that are intended for use at the OMEGA facility, NIF and Russian laser facility. The compression and burning characteristics, which were obtained using various numerical codes of different scientific groups, are compared. The data indicate good agreement between the numerical results. Various sources of target irradiation inhomogeneity and their influence on the implosion parameters are considered. The nominal scales of these disturbances for various facilities are close to each other. The main negative effect on the efficiency of compression and burning is due to the accidental offset of the target from the center of the chamber.

Performance of High-Convergence, Layered DT Implosions on Power-Scaling Experiments at National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smalyuk, V. A.; Atherton, L. J.; Benedetti, L. R.

The radiation-driven, low-adiabat, cryogenic DT layered plastic capsule implosions were carried out on the National Ignition Facility (NIF) to study the sensitivity of performance to peak power and drive duration. An implosion with extended drive and at reduced peak power of 350 TW achieved the highest compression with fuel areal density of ~1.3±0.1 g/cm 2, representing a significant step from previously measured ~1.0 g/cm 2 toward a goal of 1.5 g/cm 2. Moreover, for future experiments will focus on understanding and mitigating hydrodynamic instabilities and mix, and improving symmetry required to reach the threshold for thermonuclear ignition on NIF.

Performance of High-Convergence, Layered DT Implosions on Power-Scaling Experiments at National Ignition Facility

DOE PAGES

Smalyuk, V. A.; Atherton, L. J.; Benedetti, L. R.; ...

2013-10-19

The radiation-driven, low-adiabat, cryogenic DT layered plastic capsule implosions were carried out on the National Ignition Facility (NIF) to study the sensitivity of performance to peak power and drive duration. An implosion with extended drive and at reduced peak power of 350 TW achieved the highest compression with fuel areal density of ~1.3±0.1 g/cm 2, representing a significant step from previously measured ~1.0 g/cm 2 toward a goal of 1.5 g/cm 2. Moreover, for future experiments will focus on understanding and mitigating hydrodynamic instabilities and mix, and improving symmetry required to reach the threshold for thermonuclear ignition on NIF.

Numerical modeling of the sensitivity of x-ray driven implosions to low-mode flux asymmetries.

PubMed

Scott, R H H; Clark, D S; Bradley, D K; Callahan, D A; Edwards, M J; Haan, S W; Jones, O S; Spears, B K; Marinak, M M; Town, R P J; Norreys, P A; Suter, L J

2013-02-15

The sensitivity of inertial confinement fusion implosions, of the type performed on the National Ignition Facility (NIF) [1], to low-mode flux asymmetries is investigated numerically. It is shown that large-amplitude, low-order mode shapes (Legendre polynomial P(4), resulting from low-order flux asymmetries, cause spatial variations in capsule and fuel momentum that prevent the deuterium and tritium (DT) "ice" layer from being decelerated uniformly by the hot spot pressure. This reduces the transfer of implosion kinetic energy to internal energy of the central hot spot, thus reducing the neutron yield. Furthermore, synthetic gated x-ray images of the hot spot self-emission indicate that P(4) shapes may be unquantifiable for DT layered capsules. Instead the positive P(4) asymmetry "aliases" itself as an oblate P(2) in the x-ray images. Correction of this apparent P(2) distortion can further distort the implosion while creating a round x-ray image. Long wavelength asymmetries may be playing a significant role in the observed yield reduction of NIF DT implosions relative to detailed postshot two-dimensional simulations.

Pulsed-power-driven cylindrical liner implosions of laser preheated fuel magnetized with an axial field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, S. A.; Herrmann, M. C.; Vesey, R. A.

2010-05-15

The radial convergence required to reach fusion conditions is considerably higher for cylindrical than for spherical implosions since the volume is proportional to r{sup 2} versus r{sup 3}, respectively. Fuel magnetization and preheat significantly lowers the required radial convergence enabling cylindrical implosions to become an attractive path toward generating fusion conditions. Numerical simulations are presented indicating that significant fusion yields may be obtained by pulsed-power-driven implosions of cylindrical metal liners onto magnetized (>10 T) and preheated (100-500 eV) deuterium-tritium (DT) fuel. Yields exceeding 100 kJ could be possible on Z at 25 MA, while yields exceeding 50 MJ could bemore » possible with a more advanced pulsed power machine delivering 60 MA. These implosions occur on a much shorter time scale than previously proposed implosions, about 100 ns as compared to about 10 mus for magnetic target fusion (MTF) [I. R. Lindemuth and R. C. Kirkpatrick, Nucl. Fusion 23, 263 (1983)]. Consequently the optimal initial fuel density (1-5 mg/cc) is considerably higher than for MTF (approx1 mug/cc). Thus the final fuel density is high enough to axially trap most of the alpha-particles for cylinders of approximately 1 cm in length with a purely axial magnetic field, i.e., no closed field configuration is required for ignition. According to the simulations, an initial axial magnetic field is partially frozen into the highly conducting preheated fuel and is compressed to more than 100 MG. This final field is strong enough to inhibit both electron thermal conduction and the escape of alpha-particles in the radial direction. Analytical and numerical calculations indicate that the DT can be heated to 200-500 eV with 5-10 kJ of green laser light, which could be provided by the Z-Beamlet laser. The magneto-Rayleigh-Taylor (MRT) instability poses the greatest threat to this approach to fusion. Two-dimensional Lasnex simulations indicate that the liner walls must have a substantial initial thickness (10-20% of the radius) so that they maintain integrity throughout the implosion. The Z and Z-Beamlet experiments are now being planned to test the various components of this concept, e.g., the laser heating of the fuel and the robustness of liner implosions to the MRT instability.« less

Hybrid-drive implosion system for ICF targets

DOEpatents

Mark, James W.

1988-08-02

Hybrid-drive implosion systems (20,40) for ICF targets (10,22,42) are described which permit a significant increase in target gain at fixed total driver energy. The ICF target is compressed in two phases, an initial compression phase and a final peak power phase, with each phase driven by a separate, optimized driver. The targets comprise a hollow spherical ablator (12) surroundingly disposed around fusion fuel (14). The ablator is first compressed to higher density by a laser system (24), or by an ion beam system (44), that in each case is optimized for this initial phase of compression of the target. Then, following compression of the ablator, energy is directly delivered into the compressed ablator by an ion beam driver system (30,48) that is optimized for this second phase of operation of the target. The fusion fuel (14) is driven, at high gain, to conditions wherein fusion reactions occur. This phase separation allows hydrodynamic efficiency and energy deposition uniformity to be individually optimized, thereby securing significant advantages in energy gain. In additional embodiments, the same or separate drivers supply energy for ICF target implosion.

Hybrid-drive implosion system for ICF targets

DOEpatents

Mark, James W.

1988-01-01

Hybrid-drive implosion systems (20,40) for ICF targets (10,22,42) are described which permit a significant increase in target gain at fixed total driver energy. The ICF target is compressed in two phases, an initial compression phase and a final peak power phase, with each phase driven by a separate, optimized driver. The targets comprise a hollow spherical ablator (12) surroundingly disposed around fusion fuel (14). The ablator is first compressed to higher density by a laser system (24), or by an ion beam system (44), that in each case is optimized for this initial phase of compression of the target. Then, following compression of the ablator, energy is directly delivered into the compressed ablator by an ion beam driver system (30,48) that is optimized for this second phase of operation of the target. The fusion fuel (14) is driven, at high gain, to conditions wherein fusion reactions occur. This phase separation allows hydrodynamic efficiency and energy deposition uniformity to be individually optimized, thereby securing significant advantages in energy gain. In additional embodiments, the same or separate drivers supply energy for ICF target implosion.

Hybrid-drive implosion system for ICF targets

DOEpatents

Mark, J.W.K.

1987-10-14

Hybrid-drive implosion systems for ICF targets are described which permit a significant increase in target gain at fixed total driver energy. The ICF target is compressed in two phases, an initial compression phase and a final peak power phase, with each phase driven by a separate, optimized driver. The targets comprise a hollow spherical ablator surroundingly disposed around fusion fuel. The ablator is first compressed to higher density by a laser system, or by an ion beam system, that in each case is optimized for this initial phase of compression of the target. Then, following compression of the ablator, energy is directly delivered into the compressed ablator by an ion beam driver system that is optimized for this second phase of operation of the target. The fusion fuel is driven, at high gain, to conditions wherein fusion reactions occur. This phase separation allows hydrodynamic efficiency and energy deposition uniformity to be individually optimized, thereby securing significant advantages in energy gain. In additional embodiments, the same or separate drivers supply energy for ICF target implosion. 3 figs.

Imaging and spectroscopy of copper dopant migration of indirectly driven Beryllium capsule implosion on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Kyrala, George; Zylstra, A.; Yi, S. A.; Klline, J. L.; Shah, R. C.; Lopez, F. E.; Batha, S. A.; Doppner, T.; Thorn, D. B.; MacLaren, S.; Masters, N.; Callahan, D.; Hurricane, O.; Rice, N.; Huang, H.; Krauland, C. M.; MacDonald, M.

2017-10-01

Using beryllium, as an ablator material for indirectly driven inertial fusion, requires the use of a Copper dopant to block preheat from the hohlraum M-band radiation. However, due to the microstructure and imperfections of the capsule, some of the copper may be injected into the core of the implosion, affecting the yield and performance. Alternatively, the copper dopant may blow into the ablated plasma affecting the hohlraum performance as well. We will present some of data on time integrated imaging of the copper dopant into the core of the capsule using either the 2-dimensional multiple monochromatic imaging of the implosion, as well as the 1D spectrally resolved imaging of the copper dopant emission. In either case we found that the copper did migrate to the hot core, while fewer copper ions ablated into the hohlraum. This work performed under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396, and by LLNL under Contract DE-AC52-07NA27344.

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemke, R. W., E-mail: rwlemke@sandia.gov; Dolan, D. H.; Dalton, D. G.

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemke, R. W.; Dolan, D. H.; Dalton, D. G.

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ~1000 GPa is achieved in all cases. Lastly, these experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

DOE PAGES

Lemke, R. W.; Dolan, D. H.; Dalton, D. G.; ...

2016-01-07

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as itmore » implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ~1000 GPa is achieved in all cases. Lastly, these experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.« less

Development of new platforms for hydrodynamic instability and asymmetry measurements in deceleration phase of indirectly-driven implosions on NIF

NASA Astrophysics Data System (ADS)

Pickworth, Louisa

2017-10-01

Hydrodynamic instabilities and asymmetries are a major obstacle in the quest to achieve ignition as they cause pre-existing capsule perturbations to grow and ultimately quench the fusion burn in experiments at the National Ignition Facility (NIF). This talk will review recent developments of the experimental platforms and techniques to measure high-mode instabilities and low-mode asymmetries in the deceleration phase of implosions. These new platforms provide a natural link between the acceleration-phase experiments and neutron performance of layered deuterium-tritium implosions. In one innovative technique, self-emission from the hot spot was enhanced with argon dopant to ``self-backlight'' the shell in-flight around peak compression. Experiments with pre-imposed 2-D perturbations measured instability growth factors, while experiments with 3-D, ``native-roughness'' perturbations measured shell integrity in the deceleration phase of implosions. In a complimentary technique, the inner surface of the shell, along with its low-mode asymmetries and high-mode perturbations were visualized in implosions using x-ray emission of a high-Z dopant added to the inner surface of the capsule. These new measurements were instrumental in revealing unexpected surprises and providing improved understanding of the role of instabilities and asymmetries on implosion performance. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Symmetry Tuning with Cone Powers for Defect Induced Mix Experiment Implosions

NASA Astrophysics Data System (ADS)

Krasheninnikova, N.; Schmitt, M.; Murphy, T.; Cobble, J.; Tregillis, I.; Kyrala, G.; Bradley, P.; Hakel, P.; Hsu, S.; Kanzleiter, R.; Obrey, K.; Baumgaertel, J.; Batha, S.; DIME Team

2013-10-01

Recent DIME campaigns have demonstrated the effectiveness of cone power tuning to control the implosion symmetry in PDD configuration. DIME aims to assess the effects of mix on thermonuclear burn during a thin-shell capsule implosion. Plastic shell capsules doped with mid-Z material and filled with 5 atm of DD, are ablatively driven in a PDD laser configuration to a CR of ~7. Time-gated, spectrally and spatially resolved, dopant emission images characterize mix and temperature morphology during the implosion, while neutron diagnostics concurrently give the information about burn. Symmetry should be maintained throughout the implosions to achieve high neutron yield and optimum spectroscopic signal. 2D and 3D computer simulations using code HYDRA were performed to validate and optimize implosion symmetry using cone power tuning. In particular, Omega campaign confirmed P2 tunability with cone powers while experiments on NIF demonstrated that by reducing the energy in polar cones P2 was reduced to <1%. However, during NIF campaigns, self-emission images revealed a complex internal structure around the equator, which was not seen in HYDRA simulations and could be attributed to LPI effects. Subsequent DIME campaigns on NIF were able to eliminate this equatorial feature by reducing the laser drive substantiating the LPI hypothesis. Work performed by LANL under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the USDoE.

Studies of multi-ion-fluid yield anomaly in shock-driven implosions

NASA Astrophysics Data System (ADS)

Rinderknecht, H. G.; Rosenberg, M. J.; Li, C. K.; Zylstra, A. B.; Sio, H.; Gatu Johnson, M.; Frenje, J. A.; Séguin, F. H.; Petrasso, R. D.; Amendt, P. A.; Bellei, C.; Wilks, S. C.; Zimmerman, G.; Hoffman, N. M.; Kagan, G.; Molvig, K.; Glebov, V. Yu.; Stoeckl, C.; Marshall, F. J.; Seka, W.; Delettrez, J. A.; Sangster, T. C.; Betti, R.; Goncharov, V. N.; Meyerhofer, D. D.

2014-10-01

A. NIKROO, GA - Anomalously reduced yields relative to hydrodynamically calculated values have been observed for mixtures of D:3He compared to pure D2 gas-filled implosions in a series of shock-driven implosions at OMEGA. An extensive suite of measurements including temporal and spatial measurements of both the DD- and D3He-fusion reactions were obtained to identify the origin and physics behind this anomalous yield reduction. Measured spectral linewidths of fusion products suggest that the D ions are not thermalized to 3He during the burn, contributing to the reduced yield. The hypothesis that ion-species separation due to diffusive processes contributes to the observed yield reduction is explored using hydrodynamic simulations incorporating ion diffusion. Recent observations by Rosenberg et al. of a yield reduction with increased ion-ion mean free path do not explain the observed anomalous yield trend. Future work that will directly probe species separation with high-precision relative fusion reaction rate measurements between DD-neutrons and D3He-protons using the DualPTD instrument is discussed. This work was supported in part by the U.S. DOE, NLUF, LLE, and LLNL.

Increased shell entropy as an explanation for observed decreased shell areal densities in OMEGA implosions

NASA Astrophysics Data System (ADS)

Hoffman, Nelson; Herrmann, Hans; Kim, Yongho

2014-10-01

A reduced ion-kinetic (RIK) model used in hydrodynamic simulations has had some success in explaining time- and space-averaged observables characterizing the fusion fuel in hot low-density ICF capsule implosions driven by 1-ns 60-beam laser pulses at OMEGA. But observables characterizing the capsule shell, e.g., the areal density of 12C in a plastic shell, have proved harder to explain. Recently we have found that assuming the shell has higher entropy than expected in a 1D laser-driven RIK simulation allows an explanation of the observed values of 12C areal density, and its dependence on initial shell thickness in a set of DT-filled plastic capsules. If, for example, a 15- μm CH shell implodes on an adiabat two to three times higher than predicted in a typical unmodified RIK simulation, the calculated burn-averaged shell areal density decreases from ~80 mg/cm2 in the unmodified simulation to the observed value of ~25 mg/cm2. We discuss possible mechanisms that could lead to increased entropy in such implosions. Research supported by U.S. Department of Energy under Contract DE-AC52-06NA25396.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

DOE PAGES

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; ...

2018-03-30

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

NASA Astrophysics Data System (ADS)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; Palastro, J. P.; Short, R. W.; Froula, D. H.

2018-03-01

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ˜0.7 % laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. This allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Recent results from the first polar direct drive plastic capsule implosions on NIF

NASA Astrophysics Data System (ADS)

Schmitt, Mark J.

2012-10-01

Polar direct drive (PDD) offers a simplified platform for conducting strongly driven implosions on NIF to investigate mix, hydro-burn and ignition-relevant physics. Its successful use necessitates a firm understanding and predictive capability of its implosion characteristics including hydro performance, symmetry and yield. To assess this capability, the first two PDD implosions of deuterium filled CH capsules were recently conducted at NIF. The P2 Legendre mode symmetry seen in these implosions agreed with pre-shot predictions even though the 700kJ drive energy produced intensities that far exceeded thresholds for both Raman and Brillouin stimulated scattering. These shots were also the first to employ image backlighting driven by two laser quads. Preliminary results indicate that the yield from the uncoated 2.25 mm diameter, 42 μm thick, CH shells was reduced by about a factor of two owing to as-shot laser drive asymmetries. Similarly, a small (sim50 μm) centroid offset between the upper and lower shell hemispheres seen in the first shot appears to be indicative of the laser quad energies. Overall, the implosion trajectories agreed with pre-shot predictions of bangtime. The second shot incorporated an 80 ?m wide,10 ?m deep depression encircling the equator of the capsule. This engineered feature was imposed to test our capability to predict the effect of high-mode features on yield and mix. A predicted yield reduction factor of 3 was not observed.[4pt] In collaboration with P. A. Bradley, J. A. Cobble, P. Hakel, S. C. Hsu, N. S. Krasheninnikova, G. A. Kyrala, G. R. Magelssen, T. J. Murphy, K. A. Obrey, R. C. Shah, I. L. Tregillis and F. J. Wysocki of Los Alamos National Laboratory; M. Marinak, R. Wallace, T. Parham, M. Cowan, S. Glenn, R. Benedetti and the NIF Operations Team of Lawrence Livermore National Laboratory; R. S. Craxton and P. W. McKenty of the Univ. Rochester; P. Fitzsimmons and A. Nikroo of General Atomics; H. Rinderknecht, M. Rosenberg, and M. G. Johnson, MIT; Work supported by US DOE/NNSA, performed at LANL, operated by LANS LLC under contract DE-AC52-06NA25396.

Recent advances in theoretical and numerical studies of wire array Z-pinch in the IAPCM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Ning, E-mail: ding-ning@iapcm.ac.cn; Zhang, Yang, E-mail: ding-ning@iapcm.ac.cn; Xiao, Delong, E-mail: ding-ning@iapcm.ac.cn

2014-12-15

Fast Z-pinch has produced the most powerful X-ray radiation source in laboratory and also shows the possibility to drive inertial confinement fusion (ICF). Recent advances in wire-array Z-pinch researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper. A typical wire array Z-pinch process has three phases: wire plasma formation and ablation, implosion and the MRT instability development, stagnation and radiation. A mass injection model with azimuthal modulation coefficient is used to describe the wire initiation, and the dynamics of ablated plasmas of wire-array Z-pinches in (r, θ) geometry is numerically studied. In the implosionmore » phase, a two-dimensional(r, z) three temperature radiation MHD code MARED has been developed to investigate the development of the Magneto-Rayleigh-Taylor(MRT) instability. We also analyze the implosion modes of nested wire-array and find that the inner wire-array is hardly affected before the impaction of the outer wire-array. While the plasma accelerated to high speed in the implosion stage stagnates on the axis, abundant x-ray radiation is produced. The energy spectrum of the radiation and the production mechanism are investigated. The computational x-ray pulse shows a reasonable agreement with the experimental result. We also suggest that using alloyed wire-arrays can increase multi-keV K-shell yield by decreasing the opacity of K-shell lines. In addition, we use a detailed circuit model to study the energy coupling between the generator and the Z-pinch implosion. Recently, we are concentrating on the problems of Z-pinch driven ICF, such as dynamic hohlraum and capsule implosions. Our numerical investigations on the interaction of wire-array Z-pinches on foam convertors show qualitative agreements with experimental results on the “Qiangguang I” facility. An integrated two-dimensional simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of wire-array plasma acceleration, shock generation and production, hohlraum formation, radiation ablation and fuel compression.« less

Energy research: accelerator builders eager to aid fusion work.

PubMed

Metz, W D

1976-10-15

Useful fusion energy may be generated by means of heavy ion accelerator driven implosions if the contraints dictated by the physics and economics of thermonuclear targets and reactors can be satisfied.

Ion Thermal Decoupling and Species Separation in Shock-Driven Implosions

DOE PAGES

Rinderknecht, Hans G.; Rosenberg, M. J.; Li, C. K.; ...

2015-01-14

Here, anomalous reduction of the fusion yields by 50% and anomalous scaling of the burn-averaged ion temperatures with the ion-species fraction has been observed for the first time in D 3He-filled shock-driven inertial confinement fusion implosions. Two ion kinetic mechanisms are used to explain the anomalous observations: thermal decoupling of the D and 3He populations and diffusive species separation. The observed insensitivity of ion temperature to a varying deuterium fraction is shown to be a signature of ion thermal decoupling in shock-heated plasmas. The burn-averaged deuterium fraction calculated from the experimental data demonstrates a reduction in the average core deuteriummore » density, as predicted by simulations that use a diffusion model. Accounting for each of these effects in simulations reproduces the observed yield trends.« less

Laser imprint reduction for the critical-density foam buffered target driven by a relatively strong foot pulse at early stage of laser implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J. W., E-mail: li-jiwei@iapcm.ac.cn; He, X. T.; Institute of Applied Physics and Computational Mathematics, P. O. Box 8009, Beijing 100094

In order to reduce the effect of laser imprint in direct-drive ignition scheme a low-density foam buffered target has been proposed. This target is driven by a laser pulse with a low-intensity foot at the early stage of implosion, which heats the foam and elongates the thermal conduction zone between the laser absorption region and ablation front, increasing the thermal smoothing effect. In this paper, a relatively strong foot pulse is adopted to irradiate the critical-density foam buffered target. The stronger foot, near 1 × 10{sup 14 }W/cm{sup 2}, is able to drive a radiative shock in the low-density foam, which helps smoothmore » the shock and further reduce the effect of laser imprint. The radiative shock also forms a double ablation front structure between the two ablation fronts to further stabilize the hydrodynamics, achieving the similar results to a target with a high-Z dopant in the ablator. 2D analysis shows that for the critical-density foam buffered target irradiated by the strong foot pulse, the laser imprint can be reduced due to the radiative shock in the foam and an increased thermal smoothing effect. It seems viable for the critical-density foam buffered target to be driven by a relatively strong foot pulse with the goal of reducing the laser imprint and achieving better implosion symmetry in the direct-drive laser fusion.« less

Recent results of the Defect-Induced Mix Experiments (DIME) on NIF

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Bradley, P. A.; Cobble, J. A.; Hakel, P.; Hsu, S. C.; Krasheninnikova, N. S.; Kyrala, G. A.; Murphy, T. J.; Obrey, K. A.; Shah, R. C.; Tregillis, I. L.; Craxton, S. C.; McKenty, P. W.; Mancini, R. C.; Johns, H. M.; Joshi, Tirtha; Mayes, Daniel

2012-10-01

Investigations of directly driven implosions have been performed including experiments on Omega, and more recently NIF, to deduce the extent and uniformity of 4π and defect-induced mix near the shell/gas interface of plastic (CH) capsules filled with 5 atm D2 gas. Imaging diagnostics are used to measure the spatial variation of mix caused by the growth of non-uniformities in both capsule and laser drive characteristics. Thin (2μm) layers containing 1-2% (atomic) mid-Z dopants are imaged spectrally at late time in the implosion using multiple monochromatic imaging of H-like and He-like atomic line emission. Areal image backlighting of the capsules provides both r(t) and the symmetry of the implosion. Recent results will be shown including inferred 4π mix width, laser imprint induced mix, and mix from capsule variations.

Evolution of shock through a void in foam

NASA Astrophysics Data System (ADS)

Kim, Y.; Smidt, J. M.; Murphy, T. J.; Douglass, M. R.; Devolder, B. G.; Fincke, J. R.; Schmidt, D. W.; Cardenas, T.; Newman, S. G.; Hamilton, C. E.; Sedillo, T. J.; Los Alamos, NM 87544 Team

2016-10-01

Marble implosion is an experimental campaign intended to study the effects of heterogeneous mix on fusion burn. A spherical capsule is composed of deuterated plastic foam of controlled pore (or void) size with tritium fill in pores. As capsule implosion evolves, the initially separated deuterium and tritium will mix, producing DT yields. Void evolution during implosion is of interest for the Marble campaign. A shock tube, driven by the laser at Omega, was designed to study the evolution of a shock through a foam-filled ``void'' and subsequent void evolution. Targets were comprised of a 100 mg/cc CH foam tube containing a 200-µm diameter, lower density doped foam sphere. High-quality, radiographic images were obtained from both 2% iodine-doped in plastic foam and 15% tin-doped in aerogel foam. These experiments will be used to inform simulations.

Implosion symmetry and ρR measurements on the National Ignition Facility from nascent 27-31 MeV tertiary protons (invited) (abstract)

NASA Astrophysics Data System (ADS)

Petrasso, Richard D.

1997-01-01

Tertiary protons with birth energies from ˜27 to 30.8 MeV result from the implosion of ignition-scale inertial confinement fusion targets, such as those planned for the National Ignition Facility (NIF). Measurement of the tertiaries' slowing can provide a determination of the imploded areal density of the fuel capsule, as well as implosion asymmetry that results from anisotropy of the areal density and plasma temperature. In order to determine the utility of tertiaries for all phases of the NIF, we analyze three representative cases: a gas capsule (0.7 kJ yield); a cryogenic fuel capsule that fails to ignite (15 kJ); and a cryogenic fuel capsule that ignites and burns (13 000 kJ). In each case, tertiaries escape from the capsule and convey critical information about implosion dynamics. In addition, we show that for some gas-capsule implosions anticipated on OMEGA, tertiaries may be the only species of energetic charged particles that can determine the fuel areal density. Presently, we are building a charge-coupled device (CCD)-based charged particle spectrometer for OMEGA and for NOVA. In addition to the tertiaries, the spectrometers are sensitive to a variety of the energetic charged particles, such as knock-on protons, deuterons, and tritons, and 3He-burnup protons. In fact the latter set of charged particles will usually be the dominant signal. We will describe the basic features of the spectrometers and the measured response of the CCDs to 1-5 MeV protons, 1-5 MeV alphas, and 14 MeV neutrons (and associated gammas), the latter constitute the principal source of noise. This work is done in collaboration with C. K. Li, D. Hicks, and F. Seguin of MIT; with B. Burke of LL/MIT; with M. Cable, S. Pollaine, S. Haan, T. Bernat, T. Phillips, and J. Kilkenny of LLNL; with J, Knauer, S. Cremer, C. Verdon, and B. Kremens of University of Rochester; and with C. Ruiz and R. Leeper of SNL. This work is supported in part by LLNL Subcontract B313875 and University of Rochester Subcontract 410025-G.

Mitigating the impact of hohlraum asymmetries in National Ignition Facility implosions using capsule shims

DOE PAGES

Clark, D. S.; Weber, C. R.; Smalyuk, V. A.; ...

2016-07-22

Here, current indirect drive implosion experiments on the National Ignition Facility (NIF) 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 inmore » 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.« less

Demonstration of High Performance in Layered Deuterium-Tritium Capsule Implosions in Uranium Hohlraums at the National Ignition Facility.

PubMed

Döppner, T; Callahan, D A; Hurricane, O A; Hinkel, D E; Ma, T; Park, H-S; Berzak Hopkins, L F; Casey, D T; Celliers, P; Dewald, E L; Dittrich, T R; Haan, S W; Kritcher, A L; MacPhee, A; Le Pape, S; Pak, A; Patel, P K; Springer, P T; Salmonson, J D; Tommasini, R; Benedetti, L R; Bond, E; Bradley, D K; Caggiano, J; Church, J; Dixit, S; Edgell, D; Edwards, M J; Fittinghoff, D N; Frenje, J; Gatu Johnson, M; Grim, G; Hatarik, R; Havre, M; Herrmann, H; Izumi, N; Khan, S F; Kline, J L; Knauer, J; Kyrala, G A; Landen, O L; Merrill, F E; Moody, J; Moore, A S; Nikroo, A; Ralph, J E; Remington, B A; Robey, H F; Sayre, D; Schneider, M; Streckert, H; Town, R; Turnbull, D; Volegov, P L; Wan, A; Widmann, K; Wilde, C H; Yeamans, C

2015-07-31

We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a "high-foot" laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shape closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching 10^{16} neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel.

Mitigating the impact of hohlraum asymmetries in National Ignition Facility implosions using capsule shims

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Weber, C. R.; Smalyuk, V. A.

2016-07-15

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 ofmore » 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.« less

Demonstration of High Performance in Layered Deuterium-Tritium Capsule Implosions in Uranium Hohlraums at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Döppner, T.; Callahan, D. A.; Hurricane, O. A.

We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a “highfoot” laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shapemore » closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching 10 16 neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel.« less

Demonstration of High Performance in Layered Deuterium-Tritium Capsule Implosions in Uranium Hohlraums at the National Ignition Facility

DOE PAGES

Döppner, T.; Callahan, D. A.; Hurricane, O. A.; ...

2015-07-28

We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a “highfoot” laser pulse that were fielded in depleted uranium hohlraums at the National Ignition Facility. Recently, high-foot implosions have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium hohlraums provide a higher albedo and thus an increased drive equivalent to an additional 25 TW laser power at the peak of the drive compared to standard gold hohlraums leading to higher implosion velocity. Additionally, we observe an improved hot-spot shapemore » closer to round which indicates enhanced drive from the waist. In contrast to findings in the National Ignition Campaign, now all of our highest performing experiments have been done in uranium hohlraums and achieved total yields approaching 10 16 neutrons where more than 50% of the yield was due to additional heating of alpha particles stopping in the DT fuel.« less

Implosion of Cylindrical Cavities via Short Duration Impulsive Loading

NASA Astrophysics Data System (ADS)

Huneault, Justin; Higgins, Andrew

2014-11-01

An apparatus has been developed to study the collapse of a cylindrical cavity in gelatin subjected to a symmetric impact-driven impulsive loading. A gas-driven annular projectile is accelerated to approximately 50 m/s, at which point it impacts a gelatin casting confined by curved steel surfaces that allow a transition from an annular geometry to a cylindrically imploding motion. The implosion is visualized by a high-speed camera through a window which forms the top confining wall of the implosion cavity. The initial size of the cavity is such that the gelatin wall is two to five times thicker than the impacting projectile. Thus, during impact the compression wave which travels towards the cavity is closely followed by a rarefaction resulting from the free surface reflection of the compression wave in the projectile. As the compression wave in the gelatin reaches the inner surface, it will also reflect as a rarefaction wave. The interaction between the rarefaction waves from the gelatin and projectile free surfaces leads to large tensile stresses resulting in the spallation of a relatively thin shell. The study focuses on the effect of impact parameters on the thickness and uniformity of the imploding shell formed by the cavitation in the imploding gelatin cylinder.

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Hohlraum-Driven Ignition-Like Double-Shell Implosion Experiments on Omega: Analysis and Interpretation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amendt, P; Robey, H F; Park, H-S

2003-08-22

An experimental campaign to study hohlraum-driven ignition-like double-shell target performance using the Omega laser facility has begun. These targets are intended to incorporate as many ignition-like properties of the proposed National Ignition Facility (NIF) double-shell ignition design [1,2] as possible, given the energy constraints of the Omega laser. In particular, this latest generation of Omega double-shells is nominally predicted to produce over 99% of the (clean) DD neutron yield from the compressional or stagnation phase of the implosion as required in the NIF ignition design. By contrast, previous double-shell experience on Omega [3] was restricted to cases where a significantmore » fraction of the observed neutron yield was produced during the earlier shock convergence phase where the effects of mix are deemed negligibly small. These new targets are specifically designed to have optimized fall-line behavior for mitigating the effects of pusher-fuel mix after deceleration onset and, thereby, providing maximum neutron yield from the stagnation phase. Experimental results from this recent Omega ignition-like double-shell implosion campaign show favorable agreement with two-dimensional integrated hohlraum simulation studies when enhanced (gold) hohlraum M-band (2-5 keV) radiation is included at a level consistent with observations.« less

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE PAGES

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.; ...

2016-11-11

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Exploration of the Transition from the Hydrodynamic-like to the Strongly Kinetic Regime in Shock-Driven Implosions

DOE PAGES

Rosenberg, M. J.; Rinderknecht, H. G.; Hoffman, N. M.; ...

2014-05-05

Clear evidence of the transition from hydrodynamiclike to strongly kinetic shock-driven implosions is, for the first time, revealed and quantitatively assessed. Implosions with a range of initial equimolar D 3He gas densities show that as the density is decreased, hydrodynamic simulations strongly diverge from and increasingly over-predict the observed nuclear yields, from a factor of ~2 at 3.1 mg/cm 3 to a factor of 100 at 0.14 mg/cm 3. (The corresponding Knudsen number, the ratio of ion mean-free path to minimum shell radius, varied from 0.3 to 9; similarly, the ratio of fusion burn duration to ion diffusion time, anothermore » figure of merit of kinetic effects, varied from 0.3 to 14.) This result is shown to be unrelated to the effects of hydrodynamic mix. As a first step to garner insight into this transition, a reduced ion kinetic (RIK) model that includes gradient-diffusion and loss-term approximations to several transport processes was implemented within the framework of a one-dimensional radiation-transport code. After empirical calibration, the RIK simulations reproduce the observed yield trends, largely as a result of ion diffusion and the depletion of the reacting tail ions.« less

X-ray driven implosions at ignition relevant velocities on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meezan, N. B.; MacKinnon, A. J.; Hicks, D. G.

2013-05-15

Backlit convergent ablator experiments on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] are indirect drive implosions that study the inflight dynamics of an imploding capsule. Side-on, backlit radiography provides data used by the National Ignition Campaign to measure time-dependent properties of the capsule ablator including its center of mass radius, velocity, and unablated mass. Previously, Callahan [D. A. Callahan et al., Phys. Plasmas 19, 056305 (2012)] and Hicks [D. H. Hicks et al., Phys. Plasmas 19, 122702 (2012)] reported backlit convergent ablator experiments demonstrating velocities approaching those required for ignition. This paper focusesmore » on implosion performance data in the “rocket curve” plane, velocity vs. ablator mass. These rocket curve data, along with supporting numerical simulations, show that the nominal 195 μm-thick ignition capsule would reach the ignition velocity goal V = 370 km/s with low ablator mass remaining–below the goal of M = 0.25 mg. This finding led to experiments with thicker capsule ablators. A recent symmetry capsule experiment with a 20 μm thicker capsule driven by 520 TW, 1.86 MJ laser pulse (along with a companion backlit convergent ablator experiment) appears to have demonstrated V≥350 km/s with ablator mass remaining above the ignition goal.« less

High density laser-driven target

DOEpatents

Lindl, John D.

1981-01-01

A high density target for implosion by laser energy composed of a central quantity of fuel surrounded by a high-Z pusher shell with a low-Z ablator-pusher shell spaced therefrom forming a region filled with low-density material.

Measurements of an ablator-gas atomic mix in indirectly driven implosions at the National Ignition Facility.

PubMed

Smalyuk, V A; Tipton, R E; Pino, J E; Casey, D T; Grim, G P; Remington, B A; Rowley, D P; Weber, S V; Barrios, M; Benedetti, L R; Bleuel, D L; Bradley, D K; Caggiano, J A; Callahan, D A; Cerjan, C J; Clark, D S; Edgell, D H; Edwards, M J; Frenje, J A; Gatu-Johnson, M; Glebov, V Y; Glenn, S; Haan, S W; Hamza, A; Hatarik, R; Hsing, W W; Izumi, N; Khan, S; Kilkenny, J D; Kline, J; Knauer, J; Landen, O L; Ma, T; McNaney, J M; Mintz, M; Moore, A; Nikroo, A; Pak, A; Parham, T; Petrasso, R; Sayre, D B; Schneider, M B; Tommasini, R; Town, R P; Widmann, K; Wilson, D C; Yeamans, C B

2014-01-17

We present the first results from an experimental campaign to measure the atomic ablator-gas mix in the deceleration phase of gas-filled capsule implosions on the National Ignition Facility. Plastic capsules containing CD layers were filled with tritium gas; as the reactants are initially separated, DT fusion yield provides a direct measure of the atomic mix of ablator into the hot spot gas. Capsules were imploded with x rays generated in hohlraums with peak radiation temperatures of ∼294  eV. While the TT fusion reaction probes conditions in the central part (core) of the implosion hot spot, the DT reaction probes a mixed region on the outer part of the hot spot near the ablator-hot-spot interface. Experimental data were used to develop and validate the atomic-mix model used in two-dimensional simulations.

Metal liner-driven quasi-isentropic compression of deuterium

NASA Astrophysics Data System (ADS)

Weinwurm, Marcus; Bland, Simon N.; Chittenden, Jeremy P.

2013-09-01

Properties of degenerate hydrogen and deuterium (D) at pressures of the order of terapascals are of key interest to Planetary Science and Inertial Confinement Fusion. In order to recreate these conditions in the laboratory, we present a scheme, where a metal liner drives a cylindrically convergent quasi-isentropic compression in a D fill. We first determined an external pressure history for driving a self-similar implosion of a D shell from a fictitious flow simulation [D. S. Clark and M. Tabak, Nucl. Fusion 47, 1147 (2007)]. Then, it is shown that this D implosion can be recreated inside a beryllium liner by shaping the current pulse. For a peak current of 10.8 MA cold and nearly isochoric D is assembled at around 12 500 kg/m3. Finally, our two-dimensional Gorgon simulations show the robustness of the implosion method to the magneto-Rayleigh-Taylor instability when using a sufficiently thick liner.

LLE Review Quarterly Report (January-March 2002). Volume 90

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donaldson, William R.

2002-03-01

This volume of the LLE Review, covering January-March 2002, features “First Results from Cryogenic Target Implosions on OMEGA” by C. Stoeckl et al. (p. 49). This article describes initial results from direct-drive spherical cryogenic target implosions on the 60-beam OMEGA laser system. These experiments are part of the scientific base leading to direct-drive ignition implosions planned for the National Ignition Facility (NIF). Results shown include neutron yield, secondary-neutron and proton yields, the time of peak neutron emission, and both time-integrated and time-resolved x-ray images of the imploding core. The experimental values are compared with 1-D numerical simulations. The target withmore » an ice-layer nonuniformity of srms = 9 mm showed 30% of the 1-D predicted neutron yield. These initial results are encouraging for future cryogenic implosions on OMEGA and the NIF. Other articles in this issue are titled the following: Equation-of-State Measurements of Porous Materials on OMEGA: Numerical Modeling; Observations of Modulated Shock Waves in Solid Targets Driven by Spatially Modulated Laser Beams; Time-Dependent Electron Thermal Flux Inhibition in direct-Drive Laser Implosions; Precision Spectral Sculpting of Broadband FM Pulses Amplified in a Narrowband Medium; Electric-Field-Induced Motion of Polymer Cholesteric Liquid Crystal Flakes in a Moderately Conductive Fluid; and, Femtosecond Response of a Freestanding LT-GaAs Photoconductive Switch.« less

Modeling, measuring, and mitigating instability growth in liner implosions on Z

NASA Astrophysics Data System (ADS)

Peterson, Kyle

2015-11-01

Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. In this talk, we will discuss the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. We present simulations that show electro-thermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent magneto-Rayleigh-Taylor (MRT) instability growth. We discuss measurement results from experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electro-thermal instability growth on well-characterized initially solid aluminum or beryllium rods driven with a 20 MA, 100 ns risetime current pulse. These measurements show good agreement with electro-thermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone. Recent experiments have confirmed simulation predictions of dramatically reduced instability growth in solid metallic rods when thick dielectric coatings are used to mitigate density perturbations arising from the electro-thermal instability. These results provide further evidence that the inherent surface roughness of the target is not the dominant seed for the MRT instability, in contrast with most inertial confinement fusion approaches. These results suggest a new technique for substantially reducing the integral MRT growth in magnetically driven implosions. Indeed, recent results on the Z facility with 100 km/s Al and Be liner implosions show substantially reduced growth. These new results include axially magnetized, CH-coated beryllium liner radiographs in which the inner liner surface is observed to be remarkably straight and uniform at a radius of about 120 microns (convergence ratio ~20). Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

Mitigating the impact of hohlraum asymmetries in National Ignition Facility implosions using capsule shims

NASA Astrophysics Data System (ADS)

Clark, Daniel; Weber, Christopher; Smalyuk, Vladimir; Robey, Harry; Kritcher, Andrea; Milovich, Jose; Salmonson, Jay

2016-10-01

Current indirect drive implosion experiments on the National Ignition Facility (NIF) 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. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Influence and measurement of mass ablation in ICF implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spears, B K; Hicks, D; Velsko, C

2007-09-05

Point design ignition capsules designed for the National Ignition Facility (NIF) currently use an x-ray-driven Be(Cu) ablator to compress the DT fuel. Ignition specifications require that the mass of unablated Be(Cu), called residual mass, be known to within 1% of the initial ablator mass when the fuel reaches peak velocity. The specifications also require that the implosion bang time, a surrogate measurement for implosion velocity, be known to +/- 50 ps RMS. These specifications guard against several capsule failure modes associated with low implosion velocity or low residual mass. Experiments designed to measure and to tune experimentally the amount ofmore » residual mass are being developed as part of the National Ignition Campaign (NIC). Tuning adjustments of the residual mass and peak velocity can be achieved using capsule and laser parameters. We currently plan to measure the residual mass using streaked radiographic imaging of surrogate tuning capsules. Alternative techniques to measure residual mass using activated Cu debris collection and proton spectrometry have also been developed. These developing techniques, together with bang time measurements, will allow us to tune ignition capsules to meet NIC specs.« less

Numerical Modeling of the Sensitivity of X-Ray Driven Implosions to Low-Mode Flux Asymmetries

DOE PAGES

Scott, R. H. H.; Clark, D. S.; Bradley, D. K.; ...

2013-02-01

In this study, the sensitivity of inertial confinement fusion implosions of the type performed on the National Ignition Facility (NIF) [1] to low-mode flux asymmetries has been investigated numerically. It is shown that large-amplitude, low-order mode shapes (Legendre polynomial P4), resulting from associated low order flux asymmetries, cause spatial variations in capsule and fuel momentum that prevent the DT “ice” layer from being decelerated uniformly by the hot spot pressure. This reduces the transfer of kinetic to internal energy of the central hot spot, thus reducing neutron yield. Furthermore, synthetic gated x-ray images indicate that the P4 component of hotmore » spot self-emission shape is insensitive to P4 hot spot shapes, and a positive P4 asymmetry aliases itself as a negative or oblate P2 in these images. Correction of this apparent P2 distortion can further distort the implosion while creating a round x-ray image. Long wavelength asymmetries may be playing a significant role in the observed yield reduction of NIF DT implosions relative to detailed post-shot 2D simulations.« less

Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums

DOE PAGES

Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; ...

2015-06-02

High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a DT layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightlymore » oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 x 10¹⁵ neutrons, 40% of the 1D simulated yield.« less

ICF Implosions, Space-Charge Electric Fields, and Their Impact on Mix and Compression

NASA Astrophysics Data System (ADS)

Knoll, Dana; Chacon, Luis; Simakov, Andrei

2013-10-01

The single-fluid, quasi-neutral, radiation hydrodynamics codes, used to design the NIF targets, predict thermonuclear ignition for the conditions that have been achieved experimentally. A logical conclusion is that the physics model used in these codes is missing one, or more, key phenomena. Two key model-experiment inconsistencies on NIF are: 1) a lower implosion velocity than predicted by the design codes, and 2) transport of pusher material deep into the hot spot. We hypothesize that both of these model-experiment inconsistencies may be a result of a large, space-charge, electric field residing on the distinct interfaces in a NIF target. Large space-charge fields have been experimentally observed in Omega experiments. Given our hypothesis, this presentation will: 1) Develop a more complete physics picture of initiation, sustainment, and dissipation of a current-driven plasma sheath / double-layer at the Fuel-Pusher interface of an ablating plastic shell implosion on Omega, 2) Characterize the mix that can result from a double-layer field at the Fuel-Pusher interface, prior to the onset of fluid instabilities, and 3) Quantify the impact of the double-layer induced surface tension at the Fuel-Pusher interface on the peak observed implosion velocity in Omega.

Effects of alpha stopping power modelling on the ignition threshold in a directly-driven inertial confinement fusion capsule

DOE PAGES

Temporal, Mauro; Canaud, Benoit; Cayzac, Witold; ...

2017-05-25

The alpha-particle energy deposition mechanism modifies the ignition conditions of the thermonuclear Deuterium-Tritium fusion reactions, and constitutes a key issue in achieving high gain in Inertial Confinement Fusion implosions. One-dimensional hydrodynamic calculations have been performed with the code Multi-IFE to simulate the implosion of a capsule directly irradiated by a laser beam. The diffusion approximation for the alpha energy deposition has been used to optimize three laser profiles corresponding to different implosion velocities. A Monte-Carlo package has been included in Multi-IFE to calculate the alpha energy transport, and in this case the energy deposition uses both the LP and themore » BPS stopping power models. Homothetic transformations that maintain a constant implosion velocity have been used to map out the transition region between marginally-igniting and high-gain configurations. Furthermore, the results provided by the two models have been compared and it is found that – close to the ignition threshold – in order to produce the same fusion energy, the calculations performed with the BPS model require about 10% more invested energy with respect to the LP model.« less

Observation of a reflected shock in an indirectly driven spherical implosion at the national ignition facility.

PubMed

Le Pape, S; Divol, L; Berzak Hopkins, L; Mackinnon, A; Meezan, N B; Casey, D; Frenje, J; Herrmann, H; McNaney, J; Ma, T; Widmann, K; Pak, A; Grimm, G; Knauer, J; Petrasso, R; Zylstra, A; Rinderknecht, H; Rosenberg, M; Gatu-Johnson, M; Kilkenny, J D

2014-06-06

A 200  μm radius hot spot at more than 2 keV temperature, 1  g/cm^{3} density has been achieved on the National Ignition Facility using a near vacuum hohlraum. The implosion exhibits ideal one-dimensional behavior and 99% laser-to-hohlraum coupling. The low opacity of the remaining shell at bang time allows for a measurement of the x-ray emission of the reflected central shock in a deuterium plasma. Comparison with 1D hydrodynamic simulations puts constraints on electron-ion collisions and heat conduction. Results are consistent with classical (Spitzer-Harm) heat flux.

Fast heating of ultrahigh-density plasma as a step towards laser fusion ignition.

PubMed

Kodama, R; Norreys, P A; Mima, K; Dangor, A E; Evans, R G; Fujita, H; Kitagawa, Y; Krushelnick, K; Miyakoshi, T; Miyanaga, N; Norimatsu, T; Rose, S J; Shozaki, T; Shigemori, K; Sunahara, A; Tampo, M; Tanaka, K A; Toyama, Y; Yamanaka, T; Zepf, M

2001-08-23

Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 108 K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves, but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately; however, this 'fast ignitor' approach also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.

Backlighting Direct-Drive Cryogenic DT Implosions on OMEGA

NASA Astrophysics Data System (ADS)

Stoeckl, C.

2016-10-01

X-ray backlighting has been frequently used to measure the in-flight characteristics of an imploding shell in both direct- and indirect-drive inertial confinement fusion implosions. These measurements provide unique insight into the early time and stagnation stages of an implosion and guide the modeling efforts to improve the target designs. Backlighting a layered DT implosion on OMEGA is a particular challenge because the opacity of the DT shell is low, the shell velocity is high, the size and wall thickness of the shell is small, and the self-emission from the hot core at the onset of burn is exceedingly bright. A framing-camera-based crystal imaging system with a Si Heα backlighter at 1.865keV driven by 10-ps short pulses from OMEGA EP was developed to meet these radiography challenges. A fast target inserter was developed to accurately place the Si backlighter foil at a distance of 5 mm to the implosion target following the removal of the cryogenic shroud and an ultra-stable triggering system was implemented to reliably trigger the framing camera coincident with the arrival of the OMEGA EP pulse. This talk will report on a series of implosions in which the DT shell is imaged for a range of convergence ratios and in-flight aspect ratios. The images acquired have been analyzed for low-mode shape variations, the DT shell thickness, the level of ablator mixing into the DT fuel (even 0.1% of carbon mix can be reliably inferred), the areal density of the DT shell, and the impact of the support stalk. The measured implosion performance will be compared with hydrodynamic simulations that include imprint (up to mode 200), cross-beam energy transfer, nonlocal thermal transport, and initial low-mode perturbations such as power imbalance and target misalignment. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

A near one-dimensional 2-shock indirectly driven implosion at convergence ratio 30

NASA Astrophysics Data System (ADS)

MacLaren, Steve

2017-10-01

Inertial confinement fusion implosions at the National Ignition Facility, while successfully demonstrating self-heating due to alpha-particle deposition, have fallen short of the performance predicted by one-dimensional multi-physics implosion simulations. The current understanding, based on simulations as well as experimental evidence, suggests that the principle reason for the disagreement is a breeching of the cold fuel assembly at stagnation which would otherwise completely confine the hot spot. 3-D simulations indicate a combination of low-mode symmetry swings and ablation-front hydrodynamic instability seeded by engineering features such as the capsule tent and fill tube lead to localized thinning and perforation of the stagnated fuel, resulting in a loss of hot spot pressure and energy. We describe a short series of experiments on the NIF designed specifically to avoid these issues in order to understand if, once they are removed, a suspended-fuel-layer deuterium-tritium implosion can achieve 1-D simulated performance. The particular implosion system combines a thick capsule shell with an elevated initial ablation temperature to minimize the ablation front perturbations from the engineering features, and incorporates a large ratio of hohlraum-to-capsule radius as a means to permit a higher degree of control over implosion symmetry. The resulting implosion at a convergence ratio of 30 was not perfectly spherically symmetric as observed by both neutron and time-resolved x-ray imaging diagnostics. However, the stagnation observables match closely the performance predicted by 1D simulations, including, when some hot spot motion is accounted for, the apparent ion temperature. We present this result along with the design for an upcoming 2-shock experiment to test whether this level of agreement with the 1D model can be achieved in the self-heating regime. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

First liquid-layer implosion experiments at the NIF

NASA Astrophysics Data System (ADS)

Zylstra, Alex

2017-10-01

Replacing the standard ice layer in an ignition design with a liquid layer allows fielding the target with a higher central vapor pressure, leading to reduced implosion convergence ratio (CR). At lower CR, the implosions are expected to be more robust to instabilities and asymmetries than standard ice-layer designs, and are also unique in that the hot spot can be primarily formed from material originating in the central fuel vapor. The first liquid-layer implosions on the National Ignition Facility (NIF) have been performed by wicking the liquid fuel into a supporting foam that lines the inside surface of the capsule. A series of shots has been conducted between CR of 12 and 20 using a HDC ablator driven by a 3-shock pulse in a near-vacuum Au hohlraum. At the lowest CR the implosion performance is well predicted by 2-D radiation-hydrodynamics calculations. However, as the CR is increased the nominal simulations do not capture the experimentally observed trends. Data-based models suggest that the hot spot formation is unexpectedly suppressed at higher convergence. The data could be explained by reduced hydrodynamic coupling efficiency, or an anomalously enhanced thermal conductivity in the mixed DT/foam material. We show that the latter hypothesis can explain observed trends in several experimental metrics, including the yield, ion temperature, and burn duration. This work was performed under the auspices of the U.S. DoE by LANL under contract DE-AC52-06NA52396.

Laser-induced damage and fracture in fused silica vacuum windows

NASA Astrophysics Data System (ADS)

Campbell, John H.; Hurst, Patricia A.; Heggins, Dwight D.; Steele, William A.; Bumpas, Stanley E.

1997-05-01

Laser induced damage, that initiates catastrophic fracture, has been observed in large, fused silica lenses that also serve as vacuum barriers in high-fluence positions on the Nova and Beamlet lasers. In nearly all cases damage occurs on the vacuum side of the lens. The damage can lead to catastrophic crack growth if the flaw size exceeds the critical flaw size for SiO2. If the elastic stored energy in the lens in high enough, the lens will fracture into many pieces resulting in an implosion. The consequences of such an implosion can be severe, particularly for large vacuum systems. Three parameters control the degree of fracture in the vacuum barrier window: (1) the elastic stored energy, (2) the ratio of the window thickness to flaw depth and (3) secondary crack propagation. Fracture experiments have ben carried our on 15-cm diameter fused silica windows that contain surface flaws caused by laser damage. The results of these experiments, combined with data from window failures on Beamlet and Nova have been sued to develop design criteria for a 'fail-safe' lens. Specifically the window must be made thick enough such that the peak tensile stress is less than 500 psi and the corresponding ratio of the thickness to critical flaw size is less than 6. Under these conditions a properly mounted window, upon failure, will break into only tow pieces and will not implode. One caveat to these design criteria is that the air leak through the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments 'lock' in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase leading to further crack growth.

Different structures formed at HII boundaries

NASA Astrophysics Data System (ADS)

Miao, Jingqi; Cornwall, Paul; Kinnear, Tim

2015-03-01

Hydrodynamic simulations on the evolution of molecular clouds (MCs) at HII boundaries are used to show that radiation driven implosion (RDI) model can create almost all of the different morphological structures, such as a single bright-rimmed cloud (BRC), fragment structure and multiple elephant trunk (ET) structures.

``Green's function'' approach & low-mode asymmetries

NASA Astrophysics Data System (ADS)

Masse, Laurent; Clark, Dan; Salmonson, Jay; MacLaren, Steve; Ma, Tammy; Khan, Shahab; Pino, Jesse; Ralph, Jo; Czajka, C.; Tipton, Robert; Landen, Otto; Kyrala, Georges; 2 Team; 1 Team

2017-10-01

Long wavelength, low mode asymmetries are believed to play a leading role in limiting the performance of current ICF implosions on NIF. These long wavelength modes are initiated and driven by asymmetries in the x-ray flux from the hohlraum; however, the underlying hydrodynamics of the implosion also act to amplify these asymmetries. The work presented here aim to deepen our understanding of the interplay of the drive asymmetries and the underlying implosion hydrodynamics in determining the final imploded configuration. This is accomplished through a synthesis of numerical modeling, analytic theory, and experimental data. In detail, we use a Green's function approach to connect the drive asymmetry seen by the capsule to the measured inflight and hot spot symmetries. The approach has been validated against a suite of numerical simulations. Ultimately, we hope this work will identify additional measurements to further constrain the asymmetries and increase hohlraum illumination design flexibility on the NIF. The technique and derivation of associated error bars will be presented. LLC, (LLNS) Contract No. DE-AC52-07NA27344.

Radiation characteristics and implosion dynamics of Z-pinch dynamic hohlraums performed on PTS facility

NASA Astrophysics Data System (ADS)

Huang, Xian Bin; Ren, Xiao Dong; Dan, Jia Kun; Wang, Kun Lun; Xu, Qiang; Zhou, Shao Tong; Zhang, Si Qun; Cai, Hong Chun; Li, Jing; Wei, Bing; Ji, Ce; Feng, Shu Ping; Wang, Meng; Xie, Wei Ping; Deng, Jian Jun

2017-09-01

The preliminary experimental results of Z-pinch dynamic hohlraums conducted on the Primary Test Stand (PTS) facility are presented herein. Six different types of dynamic hohlraums were used in order to study the influence of load parameters on radiation characteristics and implosion dynamics, including dynamic hohlraums driven by single and nested arrays with different array parameters and different foams. The PTS facility can deliver a current of 6-8 MA in the peak current and 60-70 ns in the 10%-90% rising time to dynamic hohlraum loads. A set of diagnostics monitor the implosion dynamics of plasmas, the evolution of shock waves in the foam and the axial/radial X-ray radiation, giving the key parameters characterizing the features of dynamic hohlraums, such as the trajectory and related velocity of shock waves, radiation temperature, and so on. The experimental results presented here put our future study on Z-pinch dynamic hohlraums on the PTS facility on a firm basis.

Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meezan, N. B., E-mail: meezan1@llnl.gov; Hopkins, L. F. Berzak; Pape, S. Le

2015-06-15

High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape.more » Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 10{sup 15} neutrons, 40% of the 1D simulated yield.« less

Constraints on the neutrino flux in NOvA using the near detector data

DOE PAGES

Maan, Kuldeep K.

2016-12-19

NOvA, a long-baseline neutrino oscillation experiment at Fermilab, is designed to measure electron-neutrino appearance and muon-neutrino disappearance in the NuMI beam. NOvA comprises of two finely segmented liquid scintillator detectors at 14 mrad off-axis in the NuMI beam. An accurate prediction of the neutrino flux is needed for precision oscillation and cross-section measurements. Data from the hadron-production experiments and, importantly, from the NOvA Near Detector provide powerful constraints on the muon-neutrino and electron-neutrino fluxes. In particular, the measurement of the neutrino-electron elastic scattering provides an in situ constraint on the absolute flux. Lastly, this poster presents the data-driven predictions ofmore » the NOvA muonneutrino and electron-neutrino flux, and outlines future improvements in the flux determination.« less

Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares

NASA Technical Reports Server (NTRS)

Sakai, Jun-Ichi

1992-01-01

We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic field during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion phase of the current sheets, which is driven by the converging flow derived from the magnetohydrodynamic equations. It is shown that both protons and electrons can be promptly (within 1 second) accelerated to approximately 70 MeV and approximately 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares.

Impeding hohlraum plasma stagnation in inertial-confinement fusion.

PubMed

Li, C K; Séguin, F H; Frenje, J A; Rosenberg, M J; Rinderknecht, H G; Zylstra, A B; Petrasso, R D; Amendt, P A; Landen, O L; Mackinnon, A J; Town, R P J; Wilks, S C; Betti, R; Meyerhofer, D D; Soures, J M; Hund, J; Kilkenny, J D; Nikroo, A

2012-01-13

This Letter reports the first time-gated proton radiography of the spatial structure and temporal evolution of how the fill gas compresses the wall blowoff, inhibits plasma jet formation, and impedes plasma stagnation in the hohlraum interior. The potential roles of spontaneously generated electric and magnetic fields in the hohlraum dynamics and capsule implosion are discussed. It is shown that interpenetration of the two materials could result from the classical Rayleigh-Taylor instability occurring as the lighter, decelerating ionized fill gas pushes against the heavier, expanding gold wall blowoff. This experiment showed new observations of the effects of the fill gas on x-ray driven implosions, and an improved understanding of these results could impact the ongoing ignition experiments at the National Ignition Facility.

Integration of the Super Nova early warning system with the NOvA Trigger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habig, Alec; Zirnstein, Jan

The NOvA experiment, with a baseline of 810km, samples Fermilab’s upgraded NuMI beam with a Near Detector on-site and a Far Detector (FD) at Ash River, MN, to observe oscillations of muon neutrinos. The 344,064 liquid scintillator-filled cells of the 14 kton FD provide high granularity of a large detector mass and enable us to also study non-accelerator based neutrinos with our Data Driven Trigger framework. This paper will focus on the real time integration of the SNEWS with the NOvA Trigger where we have set up an XML-RPC based messaging system to inject the SNEWS signal directly into ourmore » trigger. In conclusion, this presents a departure from the E-Mail based notification mechanism used by SNEWS in the past and allows NOvA more control over propagation and transmission timing.« less

Integration of the Super Nova early warning system with the NOvA Trigger

DOE PAGES

Habig, Alec; Zirnstein, Jan

2015-12-23

The NOvA experiment, with a baseline of 810km, samples Fermilab’s upgraded NuMI beam with a Near Detector on-site and a Far Detector (FD) at Ash River, MN, to observe oscillations of muon neutrinos. The 344,064 liquid scintillator-filled cells of the 14 kton FD provide high granularity of a large detector mass and enable us to also study non-accelerator based neutrinos with our Data Driven Trigger framework. This paper will focus on the real time integration of the SNEWS with the NOvA Trigger where we have set up an XML-RPC based messaging system to inject the SNEWS signal directly into ourmore » trigger. In conclusion, this presents a departure from the E-Mail based notification mechanism used by SNEWS in the past and allows NOvA more control over propagation and transmission timing.« less

A Numerical Model for Two-Plasmon-Decay Hot-Electron Production and Mitigation in Direct-Drive Implosions

NASA Astrophysics Data System (ADS)

Myatt, J. F.; Shaw, J. G.; Solodov, A. A.; Maximov, A. V.; Short, R. W.; Seka, W.; Follett, R. K.; Edgell, D. H.; Froula, D. H.; Goncharov, V. N.

2015-11-01

Hot-electron preheat, caused by laser-plasma instabilities, can impair the performance of inertial confinement fusion implosions. It is therefore imperative to understand processes that can generate hot electrons and to design mitigation strategies should preheat be found to be excessive at the ignition scale (laser-plasma interactions do not follow hydrodynamic scaling). For this purpose, a new 3-D model [laser-plasma simulation environment (LPSE)] has been constructed that computes hot-electron generation in direct-drive plasmas based on the assumption that two-plasmon decay is the dominant, hot-electron-producing instability. It uses an established model of TPD-driven turbulence together with a new GPU based hybrid particle method of hot-electron production. The time-dependent hot-electron power, total energy, and energy spectrum are computed and compared with data from recent OMEGA implosion experiments that have sought to mitigate TPD by the use of multilayered (mid- Z) ablators. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

High-adiabat high-foot inertial confinement fusion implosion experiments on the national ignition facility.

PubMed

Park, H-S; Hurricane, O A; Callahan, D A; Casey, D T; Dewald, E L; Dittrich, T R; Döppner, T; Hinkel, D E; Berzak Hopkins, L F; Le Pape, S; Ma, T; Patel, P K; Remington, B A; Robey, H F; Salmonson, J D; Kline, J L

2014-02-07

This Letter reports on a series of high-adiabat implosions of cryogenic layered deuterium-tritium (DT) capsules indirectly driven by a "high-foot" laser drive pulse at the National Ignition Facility. High-foot implosions have high ablation velocities and large density gradient scale lengths and are more resistant to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot. Indeed, the observed hot spot mix in these implosions was low and the measured neutron yields were typically 50% (or higher) of the yields predicted by simulation. On one high performing shot (N130812), 1.7 MJ of laser energy at a peak power of 350 TW was used to obtain a peak hohlraum radiation temperature of ∼300  eV. The resulting experimental neutron yield was (2.4±0.05)×10(15) DT, the fuel ρR was (0.86±0.063)  g/cm2, and the measured Tion was (4.2±0.16)  keV, corresponding to 8 kJ of fusion yield, with ∼1/3 of the yield caused by self-heating of the fuel by α particles emitted in the initial reactions. The generalized Lawson criteria, an ignition metric, was 0.43 and the neutron yield was ∼70% of the value predicted by simulations that include α-particle self-heating.

P2 Asymmetry of Au's M-band Flux and its smoothing effect due to high-Z ablator dopants

NASA Astrophysics Data System (ADS)

Li, Yongsheng; Zhai, Chuanlei; Ren, Guoli; Gu, Jianfa; Huo, Wenyi; Meng, Xujun; Ye, Wenhua; Lan, Ke; Zhang, Weiyan

2017-10-01

X-ray drive asymmetry is one of the main seeds of low-mode implosion asymmetry that blocks further improvement of the nuclear performance of ``high-foot'' experiments on the National Ignition Facility. More particularly, the P2 asymmetry of Au's M-band flux can also severely influence the implosion performance. Here we study the smoothing effect of mid- and/or high-Z dopants in ablator on M-band flux asymmetries, by modeling and comparing the implosion processes of a Ge-doped and a Si-doped ignition capsule driven by x-ray sources with asymmetric M-band flux. As the results, (1) mid- or high-Z dopants absorb M-band flux and re-emit isotropically, helping to smooth M-band flux arriving at the ablation front, therefore reducing the P2 asymmetries of the imploding shell and hot spot; (2) the smoothing effect of Ge-dopant is more remarkable than Si-dopant due to its higher opacity than the latter in Au's M-band; and (3) placing the doped layer at a larger radius in ablator is more efficient. Applying this effect may not be a main measure to reduce the low-mode implosion asymmetry, but might be of significance in some critical situations such as Inertial Confinement Fusion (ICF) experiments very near the performance cliffs of asymmetric x-ray drives.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milovich, J. L., E-mail: milovich1@llnl.gov; Robey, H. F.; Clark, D. S.

Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm{sup 2}, but with significantly lower total neutron yields (between 1.5 × 10{sup 14} and 5.5 × 10{sup 14}) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the “high-foot” experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expensemore » of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3–10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm{sup 2}. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.« less

Effects of alpha stopping power modelling on the ignition threshold in a directly-driven inertial confinement fusion capsule

NASA Astrophysics Data System (ADS)

Temporal, Mauro; Canaud, Benoit; Cayzac, Witold; Ramis, Rafael; Singleton, Robert L.

2017-05-01

The alpha-particle energy deposition mechanism modifies the ignition conditions of the thermonuclear Deuterium-Tritium fusion reactions, and constitutes a key issue in achieving high gain in Inertial Confinement Fusion implosions. One-dimensional hydrodynamic calculations have been performed with the code Multi-IFE [R. Ramis, J. Meyer-ter-Vehn, Comput. Phys. Commun. 203, 226 (2016)] to simulate the implosion of a capsule directly irradiated by a laser beam. The diffusion approximation for the alpha energy deposition has been used to optimize three laser profiles corresponding to different implosion velocities. A Monte-Carlo package has been included in Multi-IFE to calculate the alpha energy transport, and in this case the energy deposition uses both the LP [C.K. Li, R.D. Petrasso, Phys. Rev. Lett. 70, 3059 (1993)] and the BPS [L.S. Brown, D.L. Preston, R.L. Singleton Jr., Phys. Rep. 410, 237 (2005)] stopping power models. Homothetic transformations that maintain a constant implosion velocity have been used to map out the transition region between marginally-igniting and high-gain configurations. The results provided by the two models have been compared and it is found that - close to the ignition threshold - in order to produce the same fusion energy, the calculations performed with the BPS model require about 10% more invested energy with respect to the LP model.

Experiments and Simulations on Magnetically Driven Implosions in High Repetition Rate Dense Plasma Focus

NASA Astrophysics Data System (ADS)

Caballero Bendixsen, Luis; Bott-Suzuki, Simon; Cordaro, Samuel; Krishnan, Mahadevan; Chapman, Stephen; Coleman, Phil; Chittenden, Jeremy

2015-11-01

Results will be shown on coordinated experiments and MHD simulations on magnetically driven implosions, with an emphasis on current diffusion and heat transport. Experiments are run at a Mather-type dense plasma focus (DPF-3, Vc: 20 kV, Ip: 480 kA, E: 5.8 kJ). Typical experiments are run at 300 kA and 0.33 Hz repetition rate with different gas loads (Ar, Ne, and He) at pressures of ~ 1-3 Torr, usually gathering 1000 shots per day. Simulations are run at a 96-core HP blade server cluster using 3GHz processors with 4GB RAM per node.Preliminary results show axial and radial phase plasma sheath velocity of ~ 1x105 m/s. These are in agreement with the snow-plough model of DPFs. Peak magnetic field of ~ 1 Tesla in the radial compression phase are measured. Electron densities on the order of 1018 cm-3 anticipated. Comparison between 2D and 3D models with empirical results show a good agreement in the axial and radial phase.

Down-Bore Two-Laser Heterodyne Velocimetry of an Implosion-Driven Hypervelocity Launcher

NASA Astrophysics Data System (ADS)

Hildebrand, Myles; Huneault, Justin; Loiseau, Jason; Higgins, Andrew J.

2015-06-01

The implosion-driven launcher uses explosives to shock-compress helium, driving well-characterized projectiles to velocities exceeding 10 km/s. The masses of projectiles range between 0.1 - 10 g, and the design shows excellent scalability, reaching similar velocities across different projectile sizes. In the past, velocity measurements have been limited to muzzle velocity obtained via a high-speed videography upon the projectile exiting the launch tube. Recently, Photonic Doppler Velocimetry (PDV) has demonstrated the ability to continuously measure in-bore velocity, even in the presence of significant blow-by of high temperature helium propellant past the projectile. While a single-laser PDV is limited to approximately 8 km/s, a two-laser PDV system is developed that uses two lasers operating near 1550 nm to provide velocity measurement capabilities up to 16 km/s. The two laser PDV system is used to obtain a continuous velocity history of the projectile throughout the entire launch cycle. These continuous velocity data are used to validate models of the launcher cycle and compare different advanced concepts aimed at increasing the projectile velocity to well beyond 10 km/s.

Magnetized Plasma Compression for Fusion Energy

NASA Astrophysics Data System (ADS)

Degnan, James; Grabowski, Christopher; Domonkos, Matthew; Amdahl, David

2013-10-01

Magnetized Plasma Compression (MPC) uses magnetic inhibition of thermal conduction and enhancement of charge particle product capture to greatly reduce the temporal and spatial compression required relative to un-magnetized inertial fusion (IFE)--to microseconds, centimeters vs nanoseconds, sub-millimeter. MPC greatly reduces the required confinement time relative to MFE--to microseconds vs minutes. Proof of principle can be demonstrated or refuted using high current pulsed power driven compression of magnetized plasmas using magnetic pressure driven implosions of metal shells, known as imploding liners. This can be done at a cost of a few tens of millions of dollars. If demonstrated, it becomes worthwhile to develop repetitive implosion drivers. One approach is to use arrays of heavy ion beams for energy production, though with much less temporal and spatial compression than that envisioned for un-magnetized IFE, with larger compression targets, and with much less ambitious compression ratios. A less expensive, repetitive pulsed power driver, if feasible, would require engineering development for transient, rapidly replaceable transmission lines such as envisioned by Sandia National Laboratories. Supported by DOE-OFES.

Investigation of Spheromak Plasma Cooling through Metallic Liner Spallation during Compression

NASA Astrophysics Data System (ADS)

Ross, Keeton; Mossman, Alex; Young, William; Ivanov, Russ; O'Shea, Peter; Howard, Stephen

2016-10-01

Various magnetic-target fusion (MTF) reactor concepts involve a preliminary magnetic confinement stage, followed by a metallic liner implosion that compresses the plasma to fusion conditions. The process is repeated to produce a pulsed, net-gain energy system. General Fusion, Inc. is pursuing one scheme that involves the compression of spheromak plasmas inside a liner formed by a collapsing vortex of liquid Pb-Li. The compression is driven by focused acoustic waves launched by gas-driven piston impacts. Here we describe a project to exploring the effects of possible liner spallation during compression on the spheromaks temperature, lifetime, and stability. We employ a 1 J, 10 ns pulsed YAG laser at 532nm focused onto a thin film of Li or Al to inject a known quantity of metallic impurities into a spheromak plasma and then measure the response. Diagnostics including visible and ultraviolet spectrometers, ion Doppler, B-probes, and Thomson scattering are used for plasma characterization. We then plan to apply the trends measured under these controlled conditions to evaluate the role of wall impurities during `field shots', where spheromaks are compressed through a chemically driven implosion of an aluminum flux conserver. The hope is that with further study we could more accurately include the effect of wall impurities on the fusion yield of a reactor-scale MTF system. Experimental procedures and results are presented, along with their relation to other liner-driven, MTF schemes. -/a

Dynamic symmetry of indirectly driven inertial confinement fusion capsules on the National Ignition Facilitya)

NASA Astrophysics Data System (ADS)

Town, R. P. J.; Bradley, D. K.; Kritcher, A.; Jones, O. S.; Rygg, J. R.; Tommasini, R.; Barrios, M.; Benedetti, L. R.; Berzak Hopkins, L. F.; Celliers, P. M.; Döppner, T.; Dewald, E. L.; Eder, D. C.; Field, J. E.; Glenn, S. M.; Izumi, N.; Haan, S. W.; Khan, S. F.; Kline, J. L.; Kyrala, G. A.; Ma, T.; Milovich, J. L.; Moody, J. D.; Nagel, S. R.; Pak, A.; Peterson, J. L.; Robey, H. F.; Ross, J. S.; Scott, R. H. H.; Spears, B. K.; Edwards, M. J.; Kilkenny, J. D.; Landen, O. L.

2014-05-01

In order to achieve ignition using inertial confinement fusion it is important to control the growth of low-mode asymmetries as the capsule is compressed. Understanding the time-dependent evolution of the shape of the hot spot and surrounding fuel layer is crucial to optimizing implosion performance. A design and experimental campaign to examine sources of asymmetry and to quantify symmetry throughout the implosion has been developed and executed on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. We have constructed a large simulation database of asymmetries applied during different time intervals. Analysis of the database has shown the need to measure and control the hot-spot shape, areal density distribution, and symmetry swings during the implosion. The shape of the hot spot during final stagnation is measured using time-resolved imaging of the self-emission, and information on the shape of the fuel at stagnation can be obtained from Compton radiography [R. Tommasini et al., Phys. Plasmas 18, 056309 (2011)]. For the first time on NIF, two-dimensional inflight radiographs of gas-filled and cryogenic fuel layered capsules have been measured to infer the symmetry of the radiation drive on the capsule. These results have been used to modify the hohlraum geometry and the wavelength tuning to improve the inflight implosion symmetry. We have also expanded our shock timing capabilities by the addition of extra mirrors inside the re-entrant cone to allow the simultaneous measurement of shock symmetry in three locations on a single shot, providing asymmetry information up to Legendre mode 4. By diagnosing the shape at nearly every step of the implosion, we estimate that shape has typically reduced fusion yield by about 50% in ignition experiments.

Is drag luminosity effective in recurrent novae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, Mariko; Hachisu, Izumi

1991-06-01

A study has been made of the efficiency of frictional processes in common envelope phase at outbursts of three recurrent novae T Pyx, U Sco, and RS Oph, by using steady-state wind models. The drag luminosity is found to depend strongly on the envelope mass. It may play an important role for a relatively massive envelope of about 0.0001 solar mass or more. For recurrent novae, however, acceleration due to the drag force is not important to eject the envelope mass because of its small envelope mass. Since the drag luminosity can be neglected at the extended phase of novamore » outburst, the light curves of these recurrent novae are determined only by the wind-driven mass loss as shown by Kato (1990). 23 refs.« less

Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casey, D.  T.; Woods, D. T.; Smalyuk, V. A.

2015-05-19

The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ~2 × 10⁹ at a convergence ratio of R₀/R ~ 10 and little impact due to the growth of hydrodynamic instabilities andmore » mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated.« less

Slow magnetic monopoles search in NOvA

NASA Astrophysics Data System (ADS)

Antoshkin, Alexander; Frank, Martin

2018-04-01

The NOvA far detector is well suited for finding exotic particles due to its technical features (see [1]). One type of those exotic particles is a "slow" magnetic monopole. It is assumed that the energy deposition of such monopoles should be enough to be registered (see [2]). Measurement of the expected signals was performed on the NOvA test bench at JINR (see [3]). Result of this measurement allows us to perform slow monopole's research using NOvA software and hardware with high efficiency. As a whole, the research can lead to a discovery, or it can limit the existence of monopoles in a wide range of parameters, previously unreachable in other experiments (MACRO, SLIM, RICE, IceCube). Several special software tools have been developed. Slow Monopole Trigger has been created and implemented in the NOvA Data-Driven-Trigger system. Also, an online reconstruction algorithm has been developed and tested on 5% of the data. A technical description of these tools and current results of the analysis are presented in this work.

A New Theory of Mix in Omega Capsule Implosions

NASA Astrophysics Data System (ADS)

Knoll, Dana; Chacon, Luis; Rauenzahn, Rick; Simakov, Andrei; Taitano, William; Welser-Sherrill, Leslie

2014-10-01

We put forth a new mix model that relies on the development of a charge-separation electrostatic double-layer at the fuel-pusher interface early in the implosion of an Omega plastic ablator capsule. The model predicts a sizable pusher mix (several atom %) into the fuel. The expected magnitude of the double-layer field is consistent with recent radial electric field measurements in Omega plastic ablator implosions. Our theory relies on two distinct physics mechanisms. First, and prior to shock breakout, the formation of a double layer at the fuel-pusher interface due to fast preheat-driven ionization. The double-layer electric field structure accelerates pusher ions fairly deep into the fuel. Second, after the double-layer mix has occurred, the inward-directed fuel velocity and temperature gradients behind the converging shock transports these pusher ions inward. We first discuss the foundations of this new mix theory. Next, we discuss our interpretation of the radial electric field measurements on Omega implosions. Then we discuss the second mechanism that is responsible for transporting the pusher material, already mixed via the double-layer deep into the fuel, on the shock convergence time scale. Finally we make a connection to recent mix motivated experimental data on. This work conducted under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory, managed by LANS, LLC under Contract DE-AC52-06NA25396.

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

DOE PAGES

Taitano, William T.; Simakov, Andrei N.; Chacon, Luis; ...

2018-04-09

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICFmore » capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original. We employ the same computational setup as in O. Larroche, which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. As a result, studies of such effects are left for future work.« less

Obtaining off-Hugoniot equation of state data on solid metals at extreme pressures via pulsed-power driven cylindrical liner implosions

NASA Astrophysics Data System (ADS)

Lemke, Raymond

2015-06-01

The focus of this talk is on magnetically driven, liner implosion experiments on the Z machine (Z) in which a solid, metal tube is shocklessly compressed to multi-megabar pressure. The goal of the experiments is to collect velocimetry data that can be used in conjunction with a new optimization based analysis technique to infer the principal isentrope of the tube material over a range of pressures. For the past decade, shock impact and ramp loading experiments on Z have used planar platforms exclusively. While producing state-of-the-art results for material science, it is difficult to produce drive pressures greater than 6 Mbar in the divergent planar geometry. In contrast, a cylindrical liner implosion is convergent; magnetic drive pressures approaching 50 Mbar are possible with the available current on Z (~ 20 MA). In our cylindrical experiments, the liner comprises an inner tube composed of the sample material (e.g., Ta) of unknown equation of state, and an outer tube composed of aluminum (Al) that serves as the current carrying cathode. Internal to the sample are fielded multiple PDV (Photonic Doppler Velocimetry) probes that measure velocity of the inner free surface of the imploding sample. External to the composite liner, at much larger radius, is an Al tube that is the return current anode. VISAR (velocity interferometry system for any reflector) probes measure free surface velocity of the exploding anode. Using the latter, MHD and optimization codes are employed to solve an inverse problem that yields the current driving the liner implosion. Then, the drive current, PDV velocity, MHD and optimization codes, are used to solve another inverse problem that yields pressure vs. density on approximately the principal isentrope of the sample material. Results for Ta, Re, and Cu compressed to ~ 10 Mbar are presented. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taitano, William T.; Simakov, Andrei N.; Chacon, Luis

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICFmore » capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original. We employ the same computational setup as in O. Larroche, which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. As a result, studies of such effects are left for future work.« less

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

NASA Astrophysics Data System (ADS)

Taitano, W. T.; Simakov, A. N.; Chacón, L.; Keenan, B.

2018-05-01

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICF capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original Rygg experiments [J. R. Rygg et al., Phys. Plasmas 13, 052702 (2006)]. We employ the same computational setup as in O. Larroche [Phys. Plasmas 19, 122706 (2012)], which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. Studies of such effects are left for future work.

Shock timing experiments on the National Ignition Facility: Initial results and comparison with simulation

NASA Astrophysics Data System (ADS)

Robey, H. F.; Boehly, T. R.; Celliers, P. M.; Eggert, J. H.; Hicks, D.; Smith, R. F.; Collins, R.; Bowers, M. W.; Krauter, K. G.; Datte, P. S.; Munro, D. H.; Milovich, J. L.; Jones, O. S.; Michel, P. A.; Thomas, C. A.; Olson, R. E.; Pollaine, S.; Town, R. P. J.; Haan, S.; Callahan, D.; Clark, D.; Edwards, J.; Kline, J. L.; Dixit, S.; Schneider, M. B.; Dewald, E. L.; Widmann, K.; Moody, J. D.; Döppner, T.; Radousky, H. B.; Throop, A.; Kalantar, D.; DiNicola, P.; Nikroo, A.; Kroll, J. J.; Hamza, A. V.; Horner, J. B.; Bhandarkar, S. D.; Dzenitis, E.; Alger, E.; Giraldez, E.; Castro, C.; Moreno, K.; Haynam, C.; LaFortune, K. N.; Widmayer, C.; Shaw, M.; Jancaitis, K.; Parham, T.; Holunga, D. M.; Walters, C. F.; Haid, B.; Mapoles, E. R.; Sater, J.; Gibson, C. R.; Malsbury, T.; Fair, J.; Trummer, D.; Coffee, K. R.; Burr, B.; Berzins, L. V.; Choate, C.; Brereton, S. J.; Azevedo, S.; Chandrasekaran, H.; Eder, D. C.; Masters, N. D.; Fisher, A. C.; Sterne, P. A.; Young, B. K.; Landen, O. L.; Van Wonterghem, B. M.; MacGowan, B. J.; Atherton, J.; Lindl, J. D.; Meyerhofer, D. D.; Moses, E.

2012-04-01

Capsule implosions on the National Ignition Facility (NIF) [Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with the goal of compressing deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain a self-propagating burn wave required for fusion power gain greater than unity. These implosions are driven with a carefully tailored sequence of four shock waves that must be timed to very high precision in order to keep the DT fuel on a low adiabat. Initial experiments to measure the strength and relative timing of these shocks have been conducted on NIF in a specially designed surrogate target platform known as the keyhole target. This target geometry and the associated diagnostics are described in detail. The initial data are presented and compared with numerical simulations. As the primary goal of these experiments is to assess and minimize the adiabat in related DT implosions, a methodology is described for quantifying the adiabat from the shock velocity measurements. Results are contrasted between early experiments that exhibited very poor shock timing and subsequent experiments where a modified target geometry demonstrated significant improvement.

Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

NASA Astrophysics Data System (ADS)

Gatu Johnson, M.; Frenje, J.; Lahmann, B.; Seguin, F.; Petrasso, R.; Appelbe, B.; Chittenden, J.; Walsh, C.; Delettrez, J.; Igumenshchev, I.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Grimble, W.; Marshall, F.; Michel, T.; Stoeckl, C.; Haines, B. M.; Zylstra, A. B.

2017-10-01

Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by e.g. engineering features or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation, we report on OMEGA experiments with intentional drive asymmetry designed for testing the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The measurements are contrasted to CHIMERA, RAGE and ASTER simulations, providing insight into implosion dynamics and the relative importance of laser drive non-uniformity, stalk and offset as sources of asymmetry. The results highlight the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by the U.S. DOE, NLUF and LLE.

Down-bore two-laser heterodyne velocimetry of an implosion-driven hypervelocity launcher

NASA Astrophysics Data System (ADS)

Hildebrand, Myles; Huneault, Justin; Loiseau, Jason; Higgins, Andrew J.

2017-01-01

The implosion-driven launcher uses explosives to shock-compress helium, driving well-characterized projectiles to velocities exceeding 10 km/s. The masses of projectiles range between 0.1 - 15 g, and the design shows excellent scalability, reaching similar velocities across different projectile sizes. In the past, velocity measurements have been limited to muzzle velocity obtained via a high-speed videography upon the projectile exiting the launch tube. Recently, Photon Doppler Velocimetry (PDV) has demonstrated the ability to continuously measure in-bore velocity, even in the presence of significant blow-by of high temperature helium propellant past the projectile. While a single laser system sampled at 40 GS/s with a 13 GHz detector/scope bandwidth is limited to 8 km/s, a two-laser PDV system is developed that uses two lasers operating near 1550 nm to provide velocity measurement capabilities up to 16 km/s with the same bandwidth and sampling rate. The two-laser PDV system is used to obtain a continuous velocity history of the projectile throughout the entire launch cycle. These internal ballistics trajectories are used to compare different advanced concepts aimed at increasing the projectile velocity to well beyond 10 km/s.

Design and testing of a magnetically driven implosion peak current diagnostic

NASA Astrophysics Data System (ADS)

Hess, M. H.; Peterson, K. J.; Ampleford, D. J.; Hutsel, B. T.; Jennings, C. A.; Gomez, M. R.; Dolan, D. H.; Robertson, G. K.; Payne, S. L.; Stygar, W. A.; Martin, M. R.; Sinars, D. B.

2018-04-01

A critical component of the magnetically driven implosion experiments at Sandia National Laboratories is the delivery of high-current, 10s of MA, from the Z pulsed power facility to a target. In order to assess the performance of the experiment, it is necessary to measure the current delivered to the target. Recent Magnetized Liner Inertial Fusion (MagLIF) experiments have included velocimetry diagnostics, such as PDV (Photonic Doppler Velocimetry) or Velocity Interferometer System for Any Reflector, in the final power feed section in order to infer the load current as a function of time. However, due to the nonlinear volumetrically distributed magnetic force within a velocimetry flyer, a complete time-dependent load current unfold is typically a time-intensive process and the uncertainties in the unfold can be difficult to assess. In this paper, we discuss how a PDV diagnostic can be simplified to obtain a peak current by sufficiently increasing the thickness of the flyer. This effectively keeps the magnetic force localized to the flyer surface, resulting in fast and highly accurate measurements of the peak load current. In addition, we show the results of experimental peak load current measurements from the PDV diagnostic in recent MagLIF experiments.

Effects of the P2 M-band flux asymmetry of laser-driven gold Hohlraums on the implosion of ICF ignition capsule

NASA Astrophysics Data System (ADS)

Li, Yongsheng; Gu, Jianfa; Wu, Changshu; Song, Peng; Dai, Zhensheng; Li, Shuanggui; Li, Xin; Kang, Dongguo; Gu, Peijun; Zheng, Wudi; Zou, Shiyang; Ding, Yongkun; Lan, Ke; Ye, Wenhua; Zhang, Weiyan

2016-07-01

Low-mode asymmetries in the laser-indirect-drive inertial confinement fusion implosion experiments conducted on the National Ignition Facility [G. H. Miller et al., Nucl. Fusion 44, S228 (2004)] are deemed the main obstacles hindering further improvement of the nuclear performance of deuterium-tritium-layered capsules. The dominant seeds of these asymmetries include the P2 and P4 asymmetries of x-ray drives and P2 asymmetry introduced by the supporting "tent." Here, we explore the effects of another possible seed that can lead to low-mode asymmetric implosions, i.e., the M-band flux asymmetry (MFA) in laser-driven cylindrical gold Hohlraums. It is shown that the M-band flux facilitates the ablation and acceleration of the shell, and that positive P2 MFAs can result in negative P2 asymmetries of hot spots and positive P2 asymmetries of shell's ρR. An oblate or toroidal hot spot, depending on the P2 amplitude of MFA, forms at stagnation. The energy loss of such a hot spot via electron thermal conduction is seriously aggravated not only due to the enlarged hot spot surface but also due to the vortices that develop and help transferring thermal energy from the hotter center to the colder margin of such a hot spot. The cliffs of nuclear performance for the two methodologies of applying MFA (i.e., symmetric flux in the presence of MFA and MFA added for symmetric soft x-ray flux) are obtained locating at 9.5% and 5.0% of P2/P0 amplitudes, respectively.

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, M. J., E-mail: mros@lle.rochester.edu; Séguin, F. H.; Rinderknecht, H. G.

The significance and nature of ion kinetic effects in D{sup 3}He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N{sub K}) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatiallymore » resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N{sub K} ∼ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.

The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N K) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolvedmore » measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N K ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

NASA Astrophysics Data System (ADS)

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.; Atzeni, S.; Rinderknecht, H. G.; Hoffman, N. M.; Zylstra, A. B.; Li, C. K.; Sio, H.; Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Glebov, V. Yu.; Stoeckl, C.; Seka, W.; Marshall, F. J.; Delettrez, J. A.; Sangster, T. C.; Betti, R.; Wilks, S. C.; Pino, J.; Kagan, G.; Molvig, K.; Nikroo, A.

2015-06-01

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK ˜ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.

Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

DOE PAGES

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.; ...

2015-06-02

The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N K) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolvedmore » measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N K ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Effects of the P2 M-band flux asymmetry of laser-driven gold Hohlraums on the implosion of ICF ignition capsule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yongsheng; Graduate School, China Academy of Engineering Physics, Beijing 100088; Gu, Jianfa

Low-mode asymmetries in the laser-indirect-drive inertial confinement fusion implosion experiments conducted on the National Ignition Facility [G. H. Miller et al., Nucl. Fusion 44, S228 (2004)] are deemed the main obstacles hindering further improvement of the nuclear performance of deuterium-tritium-layered capsules. The dominant seeds of these asymmetries include the P2 and P4 asymmetries of x-ray drives and P2 asymmetry introduced by the supporting “tent.” Here, we explore the effects of another possible seed that can lead to low-mode asymmetric implosions, i.e., the M-band flux asymmetry (MFA) in laser-driven cylindrical gold Hohlraums. It is shown that the M-band flux facilitates themore » ablation and acceleration of the shell, and that positive P2 MFAs can result in negative P2 asymmetries of hot spots and positive P2 asymmetries of shell's ρR. An oblate or toroidal hot spot, depending on the P2 amplitude of MFA, forms at stagnation. The energy loss of such a hot spot via electron thermal conduction is seriously aggravated not only due to the enlarged hot spot surface but also due to the vortices that develop and help transferring thermal energy from the hotter center to the colder margin of such a hot spot. The cliffs of nuclear performance for the two methodologies of applying MFA (i.e., symmetric flux in the presence of MFA and MFA added for symmetric soft x-ray flux) are obtained locating at 9.5% and 5.0% of P2/P0 amplitudes, respectively.« less

Laser-driven magnetic-flux compression in high-energy-density plasmas.

PubMed

Gotchev, O V; Chang, P Y; Knauer, J P; Meyerhofer, D D; Polomarov, O; Frenje, J; Li, C K; Manuel, M J-E; Petrasso, R D; Rygg, J R; Séguin, F H; Betti, R

2009-11-20

The demonstration of magnetic field compression to many tens of megagauss in cylindrical implosions of inertial confinement fusion targets is reported for the first time. The OMEGA laser [T. R. Boehly, Opt. Commun. 133, 495 (1997)10.1016/S0030-4018(96)00325-2] was used to implode cylindrical CH targets filled with deuterium gas and seeded with a strong external field (>50 kG) from a specially developed magnetic pulse generator. This seed field was trapped (frozen) in the shock-heated gas fill and compressed by the imploding shell at a high implosion velocity, minimizing the effect of resistive flux diffusion. The magnetic fields in the compressed core were probed via proton deflectrometry using the fusion products from an imploding D3He target. Line-averaged magnetic fields between 30 and 40 MG were observed.

Data Driven Trigger Design and Analysis for the NOvA Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurbanov, Serdar

This thesis primarily describes analysis related to studying the Moon shadow with cosmic rays, an analysis using upward-going muons trigger data, and other work done as part of MSc thesis work conducted at Fermi National Laboratory. While at Fermilab I made hardware and software contributions to two experiments - NOvA and Mu2e. NOvA is a neutrino experiment with the primary goal of measuring parameters related to neutrino oscillation. This is a running experiment, so it's possible to provide analysis of real beam and cosmic data. Most of this work was related to the Data-Driven Trigger (DDT) system of NOvA. Themore » results of the Upward-Going muon analysis was presented at ICHEP in August 2016. The analysis demonstrates the proof of principle for a low-mass dark matter search. Mu2e is an experiment currently being built at Fermilab. Its primary goal is to detect the hypothetical neutrinoless conversion from a muon into an electron. I contributed to the production and tests of Cathode Strip Chambers (CSCs) which are required for testing the Cosmic Ray Veto (CRV) system for the experiment. This contribution is described in the last chapter along with a short description of the technical work provided for the DDT system of the NOvA experiment. All of the work described in this thesis will be extended by the next generation of UVA graduate students and postdocs as new data is collected by the experiment. I hope my eorts of have helped lay the foundation for many years of beautiful results from Mu2e and NOvA.« less

Defect Implosion Experiments (DIME) at OMEGA

NASA Astrophysics Data System (ADS)

Cobble, J. A.; Schmitt, M. J.; Tregillis, I. L.; Obrey, K. D.; Magelssen, G. R.; Wilke, M. D.; Glebov, V.; Marshall, F. J.; Kim, Y. H.; Bradley, P. A.; Batha, S. H.

2010-11-01

The Los Alamos DIME campaign involves perturbed spherical implosions, driven by 60 OMEGA beams with uniform, symmetrical illumination. D-T-filled CH-shell targets with equatorial-plane defects are designed to produce a non-spherical neutron burn region. The objectives of the DIME series are to observe the non-spherical burn with the neutron imaging system (NIS) and to simulate the physics of the neutron and x-ray production. We have demonstrated adequate neutron yield for NIS imaging with targets of diameter 860 μm. All targets are filled with 5 atm of DT. We used two separate shell thicknesses: 8 μm and 15 μm, thus testing both exploding pusher and ablative designs. Defect channel depth ranges from 0 -- 8 μm. Width is 20 -- 40 μm. Perfect targets have no defect. Numerical simulations predict enhanced x-ray emission, that is suggested by experiment. Results from a recent DIME campaign will be discussed.

Cryogenic Target-Implosion Experiments on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harding, D.R.; Meyerhofer, D.D.; Sangster, T.C.

The University of Rochester’s Laboratory for Laser Energetics has been imploding thick cryogenic targets for six years. Improvements in the Cryogenic Target Handling System and the ability to accurately design laser pulse shapes that properly time shocks and minimize electron preheat, produced high fuel areal densities in deuterium cryogenic targets (202+/-7 mg/cm^2). The areal density was inferred from the energy loss of secondary protons in the fuel (D2) shell. Targets were driven on a low final adiabat (alpha = 2) employing techniques to radially grade the adiabat (the highest adiabat at the ablation surface). The ice layer meets the target-designmore » toughness specification for DT ice of 1-um rms (all modes), while D2 ice layers average 3.0-um-rms roughness. The implosion experiments and the improvements in the quality and understanding of cryogenic targets are presented.« less

Capsule performance optimization in the National Ignition Campaigna)

NASA Astrophysics Data System (ADS)

Landen, O. L.; Boehly, T. R.; Bradley, D. K.; Braun, D. G.; Callahan, D. A.; Celliers, P. M.; Collins, G. W.; Dewald, E. L.; Divol, L.; Glenzer, S. H.; Hamza, A.; Hicks, D. G.; Hoffman, N.; Izumi, N.; Jones, O. S.; Kirkwood, R. K.; Kyrala, G. A.; Michel, P.; Milovich, J.; Munro, D. H.; Nikroo, A.; Olson, R. E.; Robey, H. F.; Spears, B. K.; Thomas, C. A.; Weber, S. V.; Wilson, D. C.; Marinak, M. M.; Suter, L. J.; Hammel, B. A.; Meyerhofer, D. D.; Atherton, J.; Edwards, J.; Haan, S. W.; Lindl, J. D.; MacGowan, B. J.; Moses, E. I.

2010-05-01

A capsule performance optimization campaign will be conducted at the National Ignition Facility [G. H. Miller et al., Nucl. Fusion 44, 228 (2004)] to substantially increase the probability of ignition by laser-driven hohlraums [J. D. Lindl et al., Phys. Plasmas 11, 339 (2004)]. The campaign will experimentally correct for residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models before proceeding to cryogenic-layered implosions and ignition attempts. The required tuning techniques using a variety of ignition capsule surrogates have been demonstrated at the OMEGA facility under scaled hohlraum and capsule conditions relevant to the ignition design and shown to meet the required sensitivity and accuracy. In addition, a roll-up of all expected random and systematic uncertainties in setting the key ignition laser and target parameters due to residual measurement, calibration, cross-coupling, surrogacy, and scale-up errors has been derived that meets the required budget.

Capsule performance optimization in the National Ignition Campaign

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landen, O. L.; Bradley, D. K.; Braun, D. G.

2010-05-15

A capsule performance optimization campaign will be conducted at the National Ignition Facility [G. H. Miller et al., Nucl. Fusion 44, 228 (2004)] to substantially increase the probability of ignition by laser-driven hohlraums [J. D. Lindl et al., Phys. Plasmas 11, 339 (2004)]. The campaign will experimentally correct for residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models before proceeding to cryogenic-layered implosions and ignition attempts. The required tuning techniques using a variety of ignition capsule surrogates have been demonstrated at the OMEGA facility under scaled hohlraum and capsule conditions relevant to the ignition designmore » and shown to meet the required sensitivity and accuracy. In addition, a roll-up of all expected random and systematic uncertainties in setting the key ignition laser and target parameters due to residual measurement, calibration, cross-coupling, surrogacy, and scale-up errors has been derived that meets the required budget.« less

X-ray shadow imprint of hydrodynamic instabilities on the surface of inertial confinement fusion capsules by the fuel fill tube

DOE PAGES

MacPhee, A. G.; Casey, D. T.; Clark, D. S.; ...

2017-03-30

Measurements of hydrodynamic instability growth for a high-density carbon ablator for indirectly driven inertial confinement fusion implosions on the National Ignition Facility are reported. We observe significant unexpected features on the capsule surface created by shadows of the capsule fill tube, as illuminated by laser-irradiated x-ray spots on the hohlraum wall. These shadows increase the spatial size and shape of the fill tube perturbation in a way that can significantly degrade performance in layered implosions compared to previous expectations. The measurements were performed at a convergence ratio of ~2 using in-flight x-ray radiography. The initial seed due to shadow imprintmore » is estimated to be equivalent to ~50–100 nm of solid ablator material. As a result, this discovery has prompted the need for a mitigation strategy for future inertial confinement fusion designs as proposed here.« less

First downscattered neutron images from Inertial Confinement Fusion experiments at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Guler, Nevzat; Aragonez, Robert J.; Archuleta, Thomas N.; Batha, Steven H.; Clark, David D.; Clark, Deborah J.; Danly, Chris R.; Day, Robert D.; Fatherley, Valerie E.; Finch, Joshua P.; Gallegos, Robert A.; Garcia, Felix P.; Grim, Gary; Hsu, Albert H.; Jaramillo, Steven A.; Loomis, Eric N.; Mares, Danielle; Martinson, Drew D.; Merrill, Frank E.; Morgan, George L.; Munson, Carter; Murphy, Thomas J.; Oertel, John A.; Polk, Paul J.; Schmidt, Derek W.; Tregillis, Ian L.; Valdez, Adelaida C.; Volegov, Petr L.; Wang, Tai-Sen F.; Wilde, Carl H.; Wilke, Mark D.; Wilson, Douglas C.; Atkinson, Dennis P.; Bower, Dan E.; Drury, Owen B.; Dzenitis, John M.; Felker, Brian; Fittinghoff, David N.; Frank, Matthias; Liddick, Sean N.; Moran, Michael J.; Roberson, George P.; Weiss, Paul; Buckles, Robert A.; Cradick, Jerry R.; Kaufman, Morris I.; Lutz, Steve S.; Malone, Robert M.; Traille, Albert

2013-11-01

Inertial Confinement Fusion experiments at the National Ignition Facility (NIF) are designed to understand and test the basic principles of self-sustaining fusion reactions by laser driven compression of deuterium-tritium (DT) filled cryogenic plastic (CH) capsules. The experimental campaign is ongoing to tune the implosions and characterize the burning plasma conditions. Nuclear diagnostics play an important role in measuring the characteristics of these burning plasmas, providing feedback to improve the implosion dynamics. The Neutron Imaging (NI) diagnostic provides information on the distribution of the central fusion reaction region and the surrounding DT fuel by collecting images at two different energy bands for primary (13-15 MeV) and downscattered (10-12 MeV) neutrons. From these distributions, the final shape and size of the compressed capsule can be estimated and the symmetry of the compression can be inferred. The first downscattered neutron images from imploding ICF capsules are shown in this paper.

X-ray shadow imprint of hydrodynamic instabilities on the surface of inertial confinement fusion capsules by the fuel fill tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacPhee, A. G.; Casey, D. T.; Clark, D. S.

Measurements of hydrodynamic instability growth for a high-density carbon ablator for indirectly driven inertial confinement fusion implosions on the National Ignition Facility are reported. We observe significant unexpected features on the capsule surface created by shadows of the capsule fill tube, as illuminated by laser-irradiated x-ray spots on the hohlraum wall. These shadows increase the spatial size and shape of the fill tube perturbation in a way that can significantly degrade performance in layered implosions compared to previous expectations. The measurements were performed at a convergence ratio of ~2 using in-flight x-ray radiography. The initial seed due to shadow imprintmore » is estimated to be equivalent to ~50–100 nm of solid ablator material. As a result, this discovery has prompted the need for a mitigation strategy for future inertial confinement fusion designs as proposed here.« less

Development of the CD symcap platform to study gas-shell mix in implosions at the National Ignition Facility

DOE PAGES

Casey, D. T.; Smalyuk, V. A.; Tipton, R. E.; ...

2014-09-09

Surrogate implosions play an important role at the National Ignition Facility (NIF) for isolating aspects of the complex physical processes associated with fully integrated ignition experiments. The newly developed CD Symcap platform has been designed to study gas-shell mix in indirectly driven, pure T₂-gas filled CH-shell implosions equipped with 4 μm thick CD layers. This configuration provides a direct nuclear signature of mix as the DT yield (above a characterized D contamination background) is produced by D from the CD layer in the shell, mixing into the T-gas core. The CD layer can be placed at different locations within themore » CH shell to probe the depth and extent of mix. CD layers placed flush with the gas-shell interface and recessed up to 8 μm have shown that most of the mix occurs at the inner-shell surface. In addition, time-gated x-ray images of the hotspot show large brightly-radiating objects traversing through the hotspot around bang-time, which are likely chunks of CH/CD plastic. This platform is a powerful new capability at the NIF for understanding mix, one of the key performance issues for ignition experiments.« less

Enthalpy generation from mixing in hohlraum-driven targets

NASA Astrophysics Data System (ADS)

Amendt, Peter; Milovich, Jose

2016-10-01

The increase in enthalpy from the physical mixing of two initially separated materials is analytically estimated and applied to ICF implosions and gas-filled hohlraums. Pressure and temperature gradients across a classical interface are shown to be the origin of enthalpy generation from mixing. The amount of enthalpy generation is estimated to be on the order of 100 Joules for a 10 micron-scale annular mixing layer between the solid deuterium-tritium fuel and the undoped high-density carbon ablator of a NIF-scale implosion. A potential resonance is found between the mixing layer thickness and gravitational (Cs2/ g) and temperature-gradient scale lengths, leading to elevated enthalpy generation. These results suggest that if mixing occurs in current capsule designs for the National Ignition Facility, the ignition margin may be appreciably eroded by the associated enthalpy of mixing. The degree of enthalpy generation from mixing of high- Z hohlraum wall material and low- Z gas fills is estimated to be on the order of 100 kJ or more for recent NIF-scale hohlraum experiments, which is consistent with the inferred missing energy based on observed delays in capsule implosion times. Work performed under the auspices of Lawrence Livermore National Security, LLC (LLNS) under Contract No. DE-AC52-07NA27344.

Bright Merger-nova Emission Powered by Magnetic Wind from a Newborn Black Hole

NASA Astrophysics Data System (ADS)

Ma, Shuai-Bing; Lei, Wei-Hua; Gao, He; Xie, Wei; Chen, Wei; Zhang, Bing; Wang, Ding-Xiong

2018-01-01

Mergers of neutron star–neutron star (NS–NS) or neutron star–black hole (NS–BH) binaries are candidate sources of gravitational waves (GWs). At least a fraction of the merger remnants should be a stellar mass BH with sub-relativistic ejecta. A collimated jet is launched via the Blandford–Znajek mechanism from the central BH to trigger a short gamma-ray burst (sGRB). At the same time, a near-isotropic wind may be driven by the Blandford–Payne mechanism (BP). In previous work, additional energy injection to the ejecta from the BP mechanism was ignored, and radioactive decay has long been thought to be the main source of the kilonova energy. In this Letter, we propose that the wind driven by the BP mechanism from the newborn BH’s disk can heat up and push the ejecta during the prompt emission phase or even at late times when there is fall-back accretion. Such a BP-powered merger-nova could be bright in the optical band even for a low-luminosity sGRB. The detection of a GW merger event with a BH clearly identified as a remnant, accompanied by a bright merger-nova, would provide robust confirmation of our model.

First Experiments with Planar Wire Arrays on U Michigan's Linear Transformer Driver

NASA Astrophysics Data System (ADS)

Safronova, A. S.; Kantsyrev, V. L.; Weller, M. E.; Shrestha, I. K.; Shlyaptseva, V. V.; Cooper, M. C.; Lorance, M.; Stafford, A.; Patel, S. G.; Steiner, A. M.; Yager-Elorriaga, D. A.; Jordan, N. M.; Gilgenbach, R. M.

2014-10-01

For petawatt-class Z-pinch accelerators, a Linear Transformer Driver (LTD)-driven accelerator promises to be (at a given pinch current and implosion time) more efficient than the conventionally used Marx-driven accelerator. Because there exists almost no data on how wire arrays radiate on LTD-based machines in the USA, it is very important to perform radiation and plasma physics studies on this new type of generator. We report on the first outcome of the new partnership with University of Michigan (UM), which resulted in successful UNR-UM experiments on the low-impedance MAIZE generator with planar wire arrays (PWA). PWA is a novel wire array load that was introduced and tested in detail on high-impedance Zebra at UNR during the last years and found to be the most efficient radiator. Implosion of Al Double PWAs of different configurations were achieved on MAIZE, observed with a set of various diagnostics which include x-ray diode detectors, x-ray spectroscopy and imaging, and shadowgraphy. Al and Mg plasmas of more than 450 eV were studied in detail. Research supported by NNSA under DOE Cooperative Agreement DE-NA0001984. S. G. Patel and A. M. Steiner supported by Sandia National Laboratories. D. A. Yager-Elorriaga supported by NSF GF.

X-ray astronomy in the laboratory with a miniature compact object produced by laser-driven implosion

NASA Astrophysics Data System (ADS)

Fujioka, Shinsuke; Takabe, Hideaki; Yamamoto, Norimasa; Salzmann, David; Wang, Feilu; Nishimura, Hiroaki; Li, Yutong; Dong, Quanli; Wang, Shoujun; Zhang, Yi; Rhee, Yong-Joo; Lee, Yong-Woo; Han, Jae-Min; Tanabe, Minoru; Fujiwara, Takashi; Nakabayashi, Yuto; Zhao, Gang; Zhang, Jie; Mima, Kunioki

2009-11-01

X-ray spectroscopy is an important tool for understanding the extreme photoionization processes that drive the behaviour of non-thermal equilibrium plasmas in compact astrophysical objects such as black holes. Even so, the distance of these objects from the Earth and the inability to control or accurately ascertain the conditions that govern their behaviour makes it difficult to interpret the origin of the features in astronomical X-ray measurements. Here, we describe an experiment that uses the implosion driven by a 3TW, 4kJ laser system to produce a 0.5keV blackbody radiator that mimics the conditions that exist in the neighbourhood of a black hole. The X-ray spectra emitted from photoionized silicon plasmas resemble those observed from the binary stars Cygnus X-3 (refs 7, 8) and Vela X-1 (refs 9, 10 11) with the Chandra X-ray satellite. As well as demonstrating the ability to create extreme radiation fields in a laboratory plasma, our theoretical interpretation of these laboratory spectra contrasts starkly with the generally accepted explanation for the origin of similar features in astronomical observations. Our experimental approach offers a powerful means to test and validate the computer codes used in X-ray astronomy.

Cosmic muon induced EM showers in NO$$\

DOE PAGES

Yadav, Nitin; Duyang, Hongyue; Shanahan, Peter; ...

2016-11-15

Here, the NuMI Off-Axis v e Appearance (NOvA) experiment is a ne appearance neutrino oscillation experiment at Fermilab. It identifies the ne signal from the electromagnetic (EM) showers induced by the electrons in the final state of neutrino interactions. Cosmic muon induced EM showers, dominated by bremsstrahlung, are abundant in NOvA far detector. We use the Cosmic Muon- Removal technique to get pure EM shower sample from bremsstrahlung muons in data. We also use Cosmic muon decay in flight EM showers which are highly pure EM showers.The large Cosmic-EM sample can be used, as data driven method, to characterize themore » EM shower signature and provides valuable checks of the simulation, reconstruction, particle identification algorithm, and calibration across the NOvA detector.« less

Cosmic muon induced EM showers in NO$$\

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Nitin; Duyang, Hongyue; Shanahan, Peter

Here, the NuMI Off-Axis v e Appearance (NOvA) experiment is a ne appearance neutrino oscillation experiment at Fermilab. It identifies the ne signal from the electromagnetic (EM) showers induced by the electrons in the final state of neutrino interactions. Cosmic muon induced EM showers, dominated by bremsstrahlung, are abundant in NOvA far detector. We use the Cosmic Muon- Removal technique to get pure EM shower sample from bremsstrahlung muons in data. We also use Cosmic muon decay in flight EM showers which are highly pure EM showers.The large Cosmic-EM sample can be used, as data driven method, to characterize themore » EM shower signature and provides valuable checks of the simulation, reconstruction, particle identification algorithm, and calibration across the NOvA detector.« less

Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusiona)

NASA Astrophysics Data System (ADS)

McBride, R. D.; Martin, M. R.; Lemke, R. W.; Greenly, J. B.; Jennings, C. A.; Rovang, D. C.; Sinars, D. B.; Cuneo, M. E.; Herrmann, M. C.; Slutz, S. A.; Nakhleh, C. W.; Ryutov, D. D.; Davis, J.-P.; Flicker, D. G.; Blue, B. E.; Tomlinson, K.; Schroen, D.; Stamm, R. M.; Smith, G. E.; Moore, J. K.; Rogers, T. J.; Robertson, G. K.; Kamm, R. J.; Smith, I. C.; Savage, M.; Stygar, W. A.; Rochau, G. A.; Jones, M.; Lopez, M. R.; Porter, J. L.; Matzen, M. K.

2013-05-01

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of either 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless ("quasi-isentropic") liner compression. Third, we present "micro-Ḃ" measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density "precursor" plasma to the axis of symmetry.

Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBride, R. D.; Martin, M. R.; Lemke, R. W.

Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of eithermore » 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless (“quasi-isentropic”) liner compression. Third, we present “micro-B-dot ” measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density “precursor” plasma to the axis of symmetry.« less

Z pinches as intense x-ray sources for high-energy density physics applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzen, M.K.

1997-05-01

Fast Z-pinch implosions can efficiently convert the stored electrical energy in a pulsed-power accelerator into x rays. These x rays are produced when an imploding cylindrical plasma, driven by the magnetic field pressure associated with very large axial currents, stagnates upon the cylindrical axis of symmetry. On the Saturn pulsed-power accelerator [R. B. Spielman {ital et al.}, in {ital Proceedings of the 2nd International Conference on Dense Z Pinches}, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] at Sandia National Laboratories, for example, currents ofmore » 6{endash}8 MA with a rise time of less than 50 ns are driven through cylindrically symmetric loads, producing implosion velocities as high as 10{sup 8}cm/s and x-ray energies exceeding 400 kJ. Hydromagnetic Rayleigh{endash}Taylor instabilities and cylindrical load symmetry are critical, limiting factors in determining the assembled plasma densities and temperatures, and thus in the x-ray energies and pulse widths that can be produced on these accelerators. In recent experiments on the Saturn accelerator, these implosion nonuniformities have been minimized by using wire arrays with as many as 192 wires. Increasing the wire number produced significant improvements in the pinched plasma quality, reproducibility, and x-ray output power. X-ray pulse widths of less than 5 ns and peak powers of 75{plus_minus}10TW have been achieved with arrays of 120 tungsten wires. Similar loads have recently been fielded on the Particle Beam Fusion Accelerator (PBFA II), producing x-ray energies in excess of 1.8 MJ at powers in excess of 160 TW. These intense x-ray sources offer the potential for performing many new basic physics and fusion-relevant experiments. {copyright} {ital 1997 American Institute of Physics.}« less

Impact of convection and resistivity on angular momentum transport in dwarf novae.

NASA Astrophysics Data System (ADS)

Scepi, N.; Lesur, G.; Dubus, G.; Flock, M.

2017-12-01

The eruptive cycles of dwarf novae are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf. This model has long been known to imply enhanced angular momentum transport in the accretion disk during outburst. This is measured by the stress to pressure ratio α, with α≈ 0.1 required in outburst compared to α≈ 0.01 in quiescence. Such an enhancement in α has recently been observed in simulations of turbulent transport driven by the magneto-rotational instability (MRI) when convection is present, without requiring a net magnetic flux. We independently recover this result by carrying out PLUTO MHD simulations of vertically stratified, radiative, shearing boxes with the thermodynamics and opacities appropriate to dwarf novae. The results are robust against the choice of vertical boundary conditions. In the quiescent state, the disk is only very weakly ionized so, in the second part of our work, we studied the impact of resistive MHD on transport.We find that the MRI-driven transport is quenched (α≈ 0) below the critical density at which the magnetic Reynolds number R_{m}≤ 10^4. This is problematic because the X-ray emission observed in quiescent systems requires ongoing accretion onto the white dwarf.

Dynamic Symmetry of Indirectly Driven ICF Capsules on NIF

NASA Astrophysics Data System (ADS)

Town, R. P. J.

2013-10-01

In order to achieve ignition it is important to control the growth of low-mode asymmetries as the capsule is compressed. Understanding the time-dependent evolution of the shape of the imploding capsule, hot spot and surrounding fuel layer is crucial to optimizing implosion performance. A design and experimental campaign to examine the sources of asymmetry and to measure the symmetry throughout the implosion has been developed and executed on the NIF. For the first time on NIF, two-dimensional radiographs of the capsule during its implosion phase have been measured to infer the symmetry of the radiation drive. Time dependent equatorial symmetry has been measured of gas-filled capsules and capsules with cryogenic DT layers. These measurements have been used to modify the hohlraum geometry and the wavelength tuning to improve the inflight implosion symmetry. The technique is being extended to study azimuthal symmetry by imaging along the hohlraum axis. We have also expanded our shock timing measurements by the addition of extra mirrors inside the re-entrant cone to allow the simultaneous measurement of shock symmetry in three locations on a single shot, providing a measurement of asymmetries up to mode 4 in both the equatorial and azimuthal planes. The shape of the hot spot during final stagnation is measured using time-resolved imaging of the self-emission, and information on the shape of the fuel at stagnation can be obtained from Compton radiography using a wire-backlighter. In addition to x-ray diagnostics, a series of neutron and proton measurements of the low-mode areal density of the fuel at peak compression and at shock-flash time have been made. This talk will discuss the new imaging techniques, the results, and the analysis of the experiments done to date and their implication for ignition on NIF. The sensitivity of the in-flight and final implosion symmetry to imposed changes will be presented and compared to model predictions. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

2-Shock layered tuning campaign

NASA Astrophysics Data System (ADS)

Masse, Laurent; Dittrich, T.; Khan, S.; Kyrala, G.; Ma, T.; MacLaren, S.; Ralph, J.; Salmonson, J.; Tipton, R.; Los Alamos Natl Lab Team; Lawrence Livermore Natl Lab Team

2016-10-01

The 2-Shock platform has been developed to maintain shell sphericity throughout the compression phase of an indirect-drive target implosion and produce a stagnating hot spot in a quasi 1D-like manner. A sub-scale, 1700 _m outer diameter, and thick, 200 _m, uniformly Silicon doped, gas-filled plastic capsule is driven inside a nominal size 5750 _m diameter ignition hohlraum. The hohlraum fill is near vacuum to reduce back-scatter and improve laser/drive coupling. A two-shock pulse of about 1 MJ of laser energy drives the capsule. The thick capsule prevents ablation front feed-through to the imploded core. This platform has demonstrated its efficiency to tune a predictable and reproducible 1-D implosion with a nearly round shape. It has been shown that the high foot performance was dominated by the local defect growth due to the ablation front instability and by the hohlraum radiation asymmetries. The idea here is to take advantage of this 2-Shock platform to design a 1D-like layered implosion and eliminates the deleterious effects of radiation asymmetries and ablation front instability growth. We present the design work and our first experimental results of this near one-dimensional 2-Shock layered design. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

Implosive accretion and outbursts of active galactic nuclei

NASA Technical Reports Server (NTRS)

Lovelace, R. V. E.; Romanova, M. M.; Newman, W. I.

1994-01-01

A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

Assisted stellar suicide: the wind-driven evolution of the recurrent nova T Pyxidis

NASA Astrophysics Data System (ADS)

Knigge, Ch.; King, A. R.; Patterson, J.

2000-12-01

We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit. Thus either the primary, the secondary, or both may currently be committing assisted stellar suicide.

Research activities in nuclear astrophysics and related areas

NASA Technical Reports Server (NTRS)

1996-01-01

NASA/GRO grant NAG 5-2081, at the University of Chicago, has provided support for a broad program of theoretical research in nuclear astrophysics and related areas, with regard to gamma-ray and hard X-ray emission from classical nova explosions. This research emphasized the possible detection of 22Na gamma-ray line emission from nearby novae involving ONeMg white dwarfs, the detailed examination of 26Al production in novae, and the possible detection of the predicted early gamma ray emission from novae that arises from the decay of the short lived, positron emitting isotopes of CNO elements. Studies of nova related problems have consumed an increasing fraction of the Principal Investigator's research efforts over the past decade. Current research addresses problems associated with the standard model for the outbursts of the classical novae: the occurrence of thermonuclear runaways (TNR) in the accreted hydrogen rich envelopes on white dwarfs in close binary systems (see, e.g., the reviews by Truran 1982; and Shara 1989). Research in progress and planned for the next three years has three main objectives: (1) to gain an improved understanding of the early evolution of the light curves of, particularly, the fastest novae; (2) to gain an improved understanding of the relative importance of the various possible mechanisms of envelope hydrogen depletion (e.g. winds, common envelope driven mass loss, and nuclear burning) to the long term evolution of novae in outburst; and (3) to seek to provide a somewhat more definitive statement of the role of classical novae in nucleosynthesis. Our proposed 2-D studies of convection during the early phases of the TNR and our systematic attempt to incorporate an improved treatment of radiation hydrodynamics into the hydrodynamic code utilized in our calculations, are particularly relevant to the first of these objectives. Further 2-D studies of the effects of common envelope evolution are intended to provide more realistic constraints on the mass depletion mechanisms. Finally, detailed calculations of the thermonuclear history of the matter ejected in novae will be carried out for representative nova configurations involving both carbon-oxygen (CO) and oxygen-neon-magnesium (ONeMg) white dwarfs.

Design calculations for NIF convergent ablator experiments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callahan, Debra; Leeper, Ramon Joe; Spears, B. K.

2010-11-01

Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics: (1) Dante measurements of hohlraum x-ray flux and spectrum, (2) streaked radiographs of the imploding ablator shell, (3) wedge range filter measurements of D-He3 proton output spectra, and (4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to providemore » an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning.« less

Analytic model for the dynamic Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R., E-mail: roberto.piriz@uclm.es; Sun, Y. B.; Tahir, N. A.

2015-06-15

A model is presented for describing the cylindrical implosion of a shock wave driven by an accelerated piston. It is based in the identification of the acceleration of the shocked mass with the acceleration of the piston. The model yields the separate paths of the piston and the shock. In addition, by considering that the shocked region evolves isentropically, the approximate profiles of all the magnitudes in the shocked region are obtained. The application to the dynamic Z-pinch is presented and the results are compared with the well known snowplow and slug models which are also derived as limiting casesmore » of the present model. The snowplow model is seen to yield a trajectory in between those of the shock and the piston. Instead, the neglect of the inertial effects in the slug model is seen to produce a too fast implosion, and the pressure uniformity is shown to lead to an unphysical instantaneous piston stopping when the shock arrives to the axis.« less

Compression Dynamics of an Indirect Drive Fast Ignition Target

NASA Astrophysics Data System (ADS)

Stephens, R. B.; Hatchett, S. A.; Turner, R. E.; Tanaka, K. A.; Kodama, R.; Soures, J.

2002-11-01

We have compared the compression of an indirectly driven cone-in-shell target, a type proposed for the fast ignition concept, with models. The experimental parameters -500 μm diameter plastic shell with 60 μm thick wall were a 1/5 scale realization of a fast ignition target designed for NIF (absorbing 180 kJ for compression and ˜30 kJ for ignition, and yielding ˜30 MJ) [1]. The implosion was backlit with 6.4 keV x-rays, and observed with a framing camera which captured the implosion from ˜2.6 to 3.3 ns after the onset. The collapsing structure was very similar to model predictions except that non-thermal m-band emissions from the hohlraum penetrated the shell and vaporized gold off the reentrant cone. This could be eliminated by changing the hohlraum composition. [1] S. Hatchett, et al., 5th Wkshp on Fast Ignition of Fusion Targets (Satellite Wkshp, 28th EPS Conf. on Contr. Fusion and Plasma Phys.), Madeira, Portugal (2001).

Spatially resolved x-ray fluorescence spectroscopy of beryllium capsule implosions at the NIF

NASA Astrophysics Data System (ADS)

MacDonald, M. J.; Bishel, D. T.; Saunders, A. M.; Scott, H. A.; Kyrala, G.; Kline, J.; MacLaren, S.; Thorn, D. B.; Yi, S. A.; Zylstra, A. B.; Falcone, R. W.; Doeppner, T.

2017-10-01

Beryllium ablators used in indirectly driven inertial confinement fusion implosions are doped with copper to prevent preheat of the cryogenic hydrogen fuel. Here, we present analysis of spatially resolved copper K- α fluorescence spectra from the beryllium ablator layer. It has been shown that K- α fluorescence spectroscopy can be used to measure plasma conditions of partially ionized dopants in high energy density systems. In these experiments, K-shell vacancies in the copper dopant are created by the hotspot emission at stagnation, resulting in K-shell fluorescence at bang time. Spatially resolved copper K- α emission spectra are compared to atomic kinetics and radiation code simulations to infer density and temperature profiles. This work was supported by the US DOE under Grant No. DE-NA0001859, under the auspices of the US DOE by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344, and by Los Alamos National Laboratory under contract DE-AC52-06NA52396.

Ram-pressure scaling and non-uniformity characterization of a spherically imploding liner formed by hypervelocity plasma jets

NASA Astrophysics Data System (ADS)

Cassibry, Jason; Dougherty, Jesse; Thompson, Seth; Hsu, Scott; Witherspoon, F. D.; University of AL in Huntsville Team; Los Alamos National Laboratory Team; HyperV Technologies Corp. Team

2014-10-01

Three-dimensional modeling of plasma liner formation and implosion is performed using the Smoothed Particle Hydrodynamics Code (SPHC) with radiation, thermal transport, and tabular equations of state (EOS), accounting for ionization, in support of a proposed 60-gun plasma liner formation experiment for plasma-jet driven magneto-inertial fusion (PJMIF). Previous SPHC modeling showed that ideal gas law scaling of peak stagnation pressure increased linearly with density and number of jets, quadratically with jet radius and velocity, and inversely with the initial jet length, while results with tabular EOS, thermal transport, and radiation have greater sensitivity to the initial jet distribution. A series of simulations are conducted to study the effects of initial jet conditions on peak ram pressure and liner non-uniformity during plasma liner implosion. The growth rate of large-amplitude density perturbations introduced by the discrete jets are computed and compared with predictions by the Bell-Plesset equation.

Impact of convection and resistivity on angular momentum transport in dwarf novae

NASA Astrophysics Data System (ADS)

Scepi, N.; Lesur, G.; Dubus, G.; Flock, M.

2018-01-01

The eruptive cycles of dwarf novae are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf. This model has long been known to imply enhanced angular momentum transport in the accretion disk during outburst. This is measured by the stress to pressure ratio α, with α ≈ 0.1 required in outburst compared to α ≈ 0.01 in quiescence. Such an enhancement in α has recently been observed in simulations of turbulent transport driven by the magneto-rotational instability (MRI) when convection is present, without requiring a net magnetic flux. We independently recover this result by carrying out PLUTO magnetohydrodynamic (MHD) simulations of vertically stratified, radiative, shearing boxes with the thermodynamics and opacities appropriate to dwarf novae. The results are robust against the choice of vertical boundary conditions. The thermal equilibrium solutions found by the simulations trace the well-known S-curve in the density-temperature plane that constitutes the core of the disk thermal-viscous instability model. We confirm that the high values of α ≈ 0.1 occur near the tip of the hot branch of the S-curve, where convection is active. However, we also present thermally stable simulations at lower temperatures that have standard values of α ≈ 0.03 despite the presence of vigorous convection. We find no simple relationship between α and the strength of the convection, as measured by the ratio of convective to radiative flux. The cold branch is only very weakly ionized so, in the second part of this work, we studied the impact of non-ideal MHD effects on transport. Ohmic dissipation is the dominant effect in the conditions of quiescent dwarf novae. We include resistivity in the simulations and find that the MRI-driven transport is quenched (α ≈ 0) below the critical density at which the magnetic Reynolds number Rm ≤ 104. This is problematic because the X-ray emission observed in quiescent systems requires ongoing accretion onto the white dwarf. We verify that these X-rays cannot self-sustain MRI-driven turbulence by photo-ionizing the disk and discuss possible solutions to the issue of accretion in quiescence.

The geographic accessibility of pharmacies in Nova Scotia

PubMed Central

Heard, Deborah; Fisher, Judith; Douillard, Jay; Muzika, Greg; Sketris, Ingrid S.

2013-01-01

Introduction: Geographic proximity is an important component of access to primary care and the pharmaceutical services of community pharmacies. Variations in access to primary care have been found between rural and urban areas in Canadian and international jurisdictions. We studied access to community pharmacies in the province of Nova Scotia. Methods: We used information on the locations of 297 community pharmacies operating in Nova Scotia in June 2011. Population estimates at the census block level and network analysis were used to study the number of Nova Scotia residents living within 800 m (walking) and 2 km and 5 km (driving) distances of a pharmacy. We then simulated the impact of pharmacy closures on geographic access in urban and rural areas. Results: We found that 40.3% of Nova Scotia residents lived within walking distance of a pharmacy; 62.6% and 78.8% lived within 2 km and 5 km, respectively. Differences between urban and rural areas were pronounced: 99.2% of urban residents lived within 5 km of a pharmacy compared with 53.3% of rural residents. Simulated pharmacy closures had a greater impact on geographic access to community pharmacies in rural areas than urban areas. Conclusion: The majority of Nova Scotia residents lived within walking or short driving distance of at least 1 community pharmacy. While overall geographic access appears to be lower than in the province of Ontario, the difference appears to be largely driven by the higher proportion of rural dwellers in Nova Scotia. Further studies should examine how geographic proximity to pharmacies influences patients’ access to traditional and specialized pharmacy services, as well as health outcomes and adherence to therapy. Can Pharm J 2013;146:39-46. PMID:23795168

The geographic accessibility of pharmacies in Nova Scotia.

PubMed

Law, Michael R; Heard, Deborah; Fisher, Judith; Douillard, Jay; Muzika, Greg; Sketris, Ingrid S

2013-01-01

Geographic proximity is an important component of access to primary care and the pharmaceutical services of community pharmacies. Variations in access to primary care have been found between rural and urban areas in Canadian and international jurisdictions. We studied access to community pharmacies in the province of Nova Scotia. We used information on the locations of 297 community pharmacies operating in Nova Scotia in June 2011. Population estimates at the census block level and network analysis were used to study the number of Nova Scotia residents living within 800 m (walking) and 2 km and 5 km (driving) distances of a pharmacy. We then simulated the impact of pharmacy closures on geographic access in urban and rural areas. We found that 40.3% of Nova Scotia residents lived within walking distance of a pharmacy; 62.6% and 78.8% lived within 2 km and 5 km, respectively. Differences between urban and rural areas were pronounced: 99.2% of urban residents lived within 5 km of a pharmacy compared with 53.3% of rural residents. Simulated pharmacy closures had a greater impact on geographic access to community pharmacies in rural areas than urban areas. The majority of Nova Scotia residents lived within walking or short driving distance of at least 1 community pharmacy. While overall geographic access appears to be lower than in the province of Ontario, the difference appears to be largely driven by the higher proportion of rural dwellers in Nova Scotia. Further studies should examine how geographic proximity to pharmacies influences patients' access to traditional and specialized pharmacy services, as well as health outcomes and adherence to therapy. Can Pharm J 2013;146:39-46.

Controlling dynamics of imploded core plasma for fast ignition

NASA Astrophysics Data System (ADS)

Nagatomo, H.; Johzaki, T.; Sunahara, A.; Shiraga, H.; Sakagami, H.; Cai, H.; Mima, K.

2010-08-01

In the Fast ignition, formation of highly compressed core plasma is one of critical issue. In this work, the effect hydrodynamic instability in cone-guided shell implosion is studied. Two-dimensional radiation hydrodynamic simulations are carried out where realistic seeds of Rayleigh-Taylor instability are imposed. Preliminary results suggest that the instability reduces implosion performance, such as implosion velocity, areal density, and maximum density. In perturbed target implosion, the break-up time of the tip of the cone is earlier than that of ideal unperturbed target implosion case. This is crucial matter for the Fast ignition because the pass for the heating laser is filled with plasma before the shot of heating laser. A sophisticated implosion design of stable and low in-flight aspect ratio is necessary for cone-guided shell implosion.

Evaluation of laser-driven ion energies for fusion fast-ignition research

NASA Astrophysics Data System (ADS)

Tosaki, S.; Yogo, A.; Koga, K.; Okamoto, K.; Shokita, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Nishimura, H.

2017-10-01

We investigate laser-driven ion acceleration using kJ-class picosecond (ps) laser pulses as a fundamental study for ion-assisted fusion fast ignition, using a newly developed Thomson-parabola ion spectrometer (TPIS). The TPIS has a space- and weight-saving design, considering its use in an laser-irradiation chamber in which 12 beams of fuel implosion laser are incident, and, at the same time, demonstrates sufficient performance with its detectable range and resolution of the ion energy required for fast-ignition research. As a fundamental study on laser-ion acceleration using a ps pulse laser, we show proton acceleration up to 40 MeV at 1 × 10^{19} W cm^{-2}. The energy conversion efficiency from the incident laser into protons higher than 6 MeV is 4.6%, which encourages the realization of fusion fast ignition by laser-driven ions.

A measurable Lawson criterion and hydro-equivalent curves for inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, C. D.; Betti, R.; Departments of Mechanical Engineering and Physics and Astronomy, University of Rochester, Rochester, New York 14623

2008-10-15

It is shown that the ignition condition (Lawson criterion) for inertial confinement fusion (ICF) can be cast in a form dependent on the only two parameters of the compressed fuel assembly that can be measured with existing techniques: the hot spot ion temperature (T{sub i}{sup h}) and the total areal density ({rho}R{sub tot}), which includes the cold shell contribution. A marginal ignition curve is derived in the {rho}R{sub tot}, T{sub i}{sup h} plane and current implosion experiments are compared with the ignition curve. On this plane, hydrodynamic equivalent curves show how a given implosion would perform with respect to themore » ignition condition when scaled up in the laser-driver energy. For 3<{sub n}<6 keV, an approximate form of the ignition condition (typical of laser-driven ICF) is {sub n}{sup 2.6}{center_dot}<{rho}R{sub tot}>{sub n}>50 keV{sup 2.6}{center_dot} g/cm{sup 2}, where <{rho}R{sub tot}>{sub n} and {sub n} are the burn-averaged total areal density and hot spot ion temperature, respectively. Both quantities are calculated without accounting for the alpha-particle energy deposition. Such a criterion can be used to determine how surrogate D{sub 2} and subignited DT target implosions perform with respect to the one-dimensional ignition threshold.« less

Hydrodynamic instability growth of three-dimensional modulations in radiation-driven implosions with “low-foot” and “high-foot” drives at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smalyuk, V. A.; Weber, C. R.; Robey, H. F.

Hydrodynamic instability growth has been studied using three-dimensional (3-D) broadband modulations by comparing “high-foot” and “low-foot” spherical plastic (CH) capsule implosions at the National Ignition Facility (NIF). The initial perturbations included capsule outer-surface roughness and capsule-mounting membranes (“tents”) that were similar to those used in a majority of implosions on NIF. The tents with thicknesses of 31-nm, 46-nm, and 109-nm were used in the experiments. The outer-surface roughness in the “low-foot” experiment was similar to the standard specification, while it was increased by ~4 times in the “high-foot” experiment to compensate for the reduced growth. The ablation-front instability growth wasmore » measured using a Hydrodynamic Growth Radiography platform at a convergence ratio of 3. The dominant capsule perturbations, generated by the tent mountings, had measured perturbation amplitudes comparable to the capsule thickness with the “low-foot” drive. These tent perturbations were reduced by ~3 to 10 times in implosions with the “high-foot” drive. Unexpectedly, the measured perturbations with initially thinner tents were either larger or similar to the measured perturbations with thicker tents for both “high-foot” and “low-foot” drives. While the measured instability growth of 3-D broadband perturbations was also significantly reduced by ~5 to 10 times with the “high-foot” drive, compared to the “low-foot” drive, the growth mitigation was stronger than expected based on previous “growth-factor” results measured with two-dimensional modulations. Lastly, one of the hypotheses to explain the results is based on the 3-D modulations of the oxygen content in the bulk of the capsule having a stronger effect on the overall growth of capsule perturbations than the outer-surface capsule roughness.« less

Hydrodynamic instability growth of three-dimensional modulations in radiation-driven implosions with “low-foot” and “high-foot” drives at the National Ignition Facility

DOE PAGES

Smalyuk, V. A.; Weber, C. R.; Robey, H. F.; ...

2017-04-11

Hydrodynamic instability growth has been studied using three-dimensional (3-D) broadband modulations by comparing “high-foot” and “low-foot” spherical plastic (CH) capsule implosions at the National Ignition Facility (NIF). The initial perturbations included capsule outer-surface roughness and capsule-mounting membranes (“tents”) that were similar to those used in a majority of implosions on NIF. The tents with thicknesses of 31-nm, 46-nm, and 109-nm were used in the experiments. The outer-surface roughness in the “low-foot” experiment was similar to the standard specification, while it was increased by ~4 times in the “high-foot” experiment to compensate for the reduced growth. The ablation-front instability growth wasmore » measured using a Hydrodynamic Growth Radiography platform at a convergence ratio of 3. The dominant capsule perturbations, generated by the tent mountings, had measured perturbation amplitudes comparable to the capsule thickness with the “low-foot” drive. These tent perturbations were reduced by ~3 to 10 times in implosions with the “high-foot” drive. Unexpectedly, the measured perturbations with initially thinner tents were either larger or similar to the measured perturbations with thicker tents for both “high-foot” and “low-foot” drives. While the measured instability growth of 3-D broadband perturbations was also significantly reduced by ~5 to 10 times with the “high-foot” drive, compared to the “low-foot” drive, the growth mitigation was stronger than expected based on previous “growth-factor” results measured with two-dimensional modulations. Lastly, one of the hypotheses to explain the results is based on the 3-D modulations of the oxygen content in the bulk of the capsule having a stronger effect on the overall growth of capsule perturbations than the outer-surface capsule roughness.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A.; Kline, J. L.; Meezan, N.

The current high-foot and related implosions have adequate CR and implosion velocity to ignite, but require improved finesse particularly in, but not limited to, implosion symmetry. This is being pursued. The challenge of controlling drive symmetry is also motivating lower convergence ratio designs. These require higher velocity implosions and are also being pursued.

Laser-driven planar Rayleigh-Taylor instability experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glendinning, S.G.; Weber, S.V.; Bell, P.

1992-08-24

We have performed a series of experiments on the Nova Laser Facility to examine the hydrodynamic behavior of directly driven planar foils with initial perturbations of varying wavelength. The foils were accelerated with a single, frequency doubled, smoothed and temporally shaped laser beam at 0.8{times}10{sup 14} W/cm{sup 2}. The experiments are in good agreement with numerical simulations using the computer codes LASNEX and ORCHID which show growth rates reduced to about 70% of classical for this nonlinear regime.

In-flight observations of low-mode ρR asymmetries in NIF implosions

DOE PAGES

Zylstra, A. B.; Frenje, J. A.; Seguin, F. H.; ...

2015-05-01

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D 3He gas-filled implosions at the National Ignition Facility produce energetic protons via D+ 3He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3-5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%,more » which are interpreted as l=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.« less

In-flight observations of low-mode ρR asymmetries in NIF implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B., E-mail: zylstra@mit.edu; Frenje, J. A.; Séguin, F. H.

2015-05-15

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D{sup 3}He gas-filled implosions at the National Ignition Facility produce energetic protons via D+{sup 3}He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3–5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳10%,more » which are interpreted as ℓ=2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained (“no-coast”), implying a significant time-dependent asymmetry in peak drive.« less

The One-Dimensional Cryogenic Implosion Campaign on OMEGA: Modeling, Experiments, and a Statistical Approach to Predict and Understand Direct-Drive Implosions

NASA Astrophysics Data System (ADS)

Betti, R.

2017-10-01

The 1-D campaign on OMEGA is aimed at validating a novel approach to design cryogenic implosion experiments and provide valuable data to improve the accuracy of 1-D physics models. This new design methodology is being tested first on low-convergence, high-adiabat (α 6 to 7) implosions and will subsequently be applied to implosions with increasing convergence up to the level required for a hydro-equivalent demonstration of ignition. This design procedure assumes that the hydrodynamic codes used in implosion designs lack the necessary physics and that measurements of implosion properties are imperfect. It also assumes that while the measurements may have significant systematic errors, the shot-to-shot variations are small and that cryogenic implosion data are reproducible as observed on OMEGA. One of the goals of the 1-D campaign is to find a mapping of the data to the code results and use the mapping relations to design future implosions. In the 1-D campaign, this predictive methodology was used to design eight implosions using a simple two-shock pulse design, leading to pre-shot predictions of yields within 5% and ion temperatures within 4% of the experimental values. These implosions have also produced the highest neutron yield of 1014 in OMEGA cryogenic implosion experiments with an areal density of 100 mg/cm2. Furthermore, the results from this campaign have been used to test the validity of the 1-D physics models used in the radiation-hydrodynamics codes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DENA0001944 and LLNL under Contract DE-AC52-07NA27344. * In collaboration with J.P. Knauer, V. Gopalaswamy, D. Patel, K.M. Woo, K.S. Anderson, A. Bose, A.R. Christopherson, V.Yu. Glebov, F.J. Marshall, S.P. Regan, P.B. Radha, C. Stoeckl, and E.M. Campbell.

Multiple Monochromatic Imaging (MMI) Status and Plans for LANL Campaigns on Omega and NIF

NASA Astrophysics Data System (ADS)

Wysocki, F. J.; Hsu, S. C.; Tregillis, I. L.; Schmitt, M. J.; Kyrala, G. A.; Martinson, D. D.; Murphy, T. J.; Mancini, R. C.; Nagayama, T.

2011-10-01

LANL's DIME (Defect Implosion Experiment) campaigns on Omega and NIF are aimed at obtaining improved understanding of defect-induced mix via experiments and simulations of directly driven high-Z doped plastic capsules with DD or DT gas fill. To this end, the MMI diagnostic has been identified as a key diagnostic for providing space and time-resolved density, temperature, and mix profiles. The high Z shell dopants used on Omega are Ti and V, and to be used on NIF are Ge and Se. This poster will discuss the following four areas of MMI-related work at LANL, in collaboration with UNR: (1) data and preliminary analysis of MMI data from FY11 Omega campaigns, (2) development of a capability to generate simulated MMI data from radiation- hydrodynamic simulations of ICF implosions, (3) design of an MMI instrument for NIF that will cover the photon energy range 9.5-16.9 keV which includes the Ge/Se, H- like/He-like, α/ β lines, and (4) the development of MMI data post- processing and spectroscopic analysis tools. Supported by DOE NNSA.

Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

NASA Astrophysics Data System (ADS)

Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Aappelbe, B.; Chittenden, J.; Walsh, C.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Marshall, F.; Michel, T.; Stoeckl, C.; Sangster, T. C.; Zylstra, A.

2016-10-01

Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by engineering features (such as stalks, fill tubes, tents, or capsule imperfections) or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation we report on an OMEGA experiment with intentionally asymmetric drive, designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The results provide insight into the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

Performance of the NOνA Data Acquisition and Trigger Systems for the full 14 kT Far Detector

NASA Astrophysics Data System (ADS)

Norman, A.; Davies, G. S.; Ding, P. F.; Dukes, E. C.; Duyan, H.; Frank, M. J.; R. C. Group; Habig, A.; Henderson, W.; Niner, E.; Mina, R.; Moren, A.; Mualem, L.; Oksuzian, Y.; Rebel, B.; Shanahan, P.; Sheshukov, A.; Tamsett, M.; Tomsen, K.; Vinton, L.; Wang, Z.; Zamorano, B.; Zirnstien, J.

2015-12-01

The NOvA experiment uses a continuous, free-running, dead-timeless data acquisition system to collect data from the 14 kT far detector. The DAQ system readouts the more than 344,000 detector channels and assembles the information into an raw unfiltered high bandwidth data stream. The NOvA trigger systems operate in parallel to the readout and asynchronously to the primary DAQ readout/event building chain. The data driven triggering systems for NOvA are unique in that they examine long contiguous time windows of the high resolution readout data and enable the detector to be sensitive to a wide range of physics interactions from those with fast, nanosecond scale signals up to processes with long delayed coincidences between hits which occur at the tens of milliseconds time scale. The trigger system is able to achieve a true 100% live time for the detector, making it sensitive to both beam spill related and off-spill physics.

Infant-mortality testing of high-energy-density capacitors used on Nova

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merritt, B.T.; Whitham, K.

1983-01-01

Nova is a solid-state large laser for inertial-confinement fusion research. Its flashlamps are driven by a 60-MJ capacitor bank. Part of this bank is being built with high-energy-density capacitors, 52-..mu..F, 22 kV, 12.5 kJ. A total of 2645 of these capacitors have been purchased from two manufacturers. Each capacitor was infant-mortality tested. The first test consisted of a high-potential test, bushing-to-case, since these capacitors have dual bushings. Then the capacitors were discharged 500 times with circuit conditions approximating the capacitors normal flashlamp load. Failure of either of these tests or if the capacitor was leaking was cause for rejection.

Plasma barodiffusion in inertial-confinement-fusion implosions: application to observed yield anomalies in thermonuclear fuel mixtures.

PubMed

Amendt, Peter; Landen, O L; Robey, H F; Li, C K; Petrasso, R D

2010-09-10

The observation of large, self-generated electric fields (≥10(9)  V/m) in imploding capsules using proton radiography has been reported [C. K. Li, Phys. Rev. Lett. 100, 225001 (2008)]. A model of pressure gradient-driven diffusion in a plasma with self-generated electric fields is developed and applied to reported neutron yield deficits for equimolar D3He [J. R. Rygg, Phys. Plasmas 13, 052702 (2006)] and (DT)3He [H. W. Herrmann, Phys. Plasmas 16, 056312 (2009)] fuel mixtures and Ar-doped deuterium fuels [J. D. Lindl, Phys. Plasmas 11, 339 (2004)]. The observed anomalies are explained as a mild loss of deuterium nuclei near capsule center arising from shock-driven diffusion in the high-field limit.

Two-Plasmon Decay Mitigation in Direct-Drive Inertial-Confinement-Fusion Experiments Using Multilayer Targets.

PubMed

Follett, R K; Delettrez, J A; Edgell, D H; Goncharov, V N; Henchen, R J; Katz, J; Michel, D T; Myatt, J F; Shaw, J; Solodov, A A; Stoeckl, C; Yaakobi, B; Froula, D H

2016-04-15

Multilayer direct-drive inertial-confinement-fusion targets are shown to significantly reduce two-plasmon decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor-of-5 reduction in hot-electron generation (>50  keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD-driven hot-electron production using a laser-plasma interaction code (lpse) that includes nonlinear and kinetic effects show good agreement with the measurements. The simulations suggest that the reduction in hot-electron production observed in the multilayer targets is primarily caused by increased electron-ion collisional damping.

Novel characterization of capsule x-ray drive at the National Ignition Facility.

PubMed

MacLaren, S A; Schneider, M B; Widmann, K; Hammer, J H; Yoxall, B E; Moody, J D; Bell, P M; Benedetti, L R; Bradley, D K; Edwards, M J; Guymer, T M; Hinkel, D E; Hsing, W W; Kervin, M L; Meezan, N B; Moore, A S; Ralph, J E

2014-03-14

Indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%-25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the data from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.

Using multiple secondary fusion products to evaluate fuel ρR, electron temperature, and mix in deuterium-filled implosions at the NIF

DOE PAGES

Rinderknecht, H. G.; Rosenberg, M. J.; Zylstra, A. B.; ...

2015-08-25

In deuterium-filled inertial confinement fusion implosions, the secondary fusion processes D( 3He,p) 4He and D(T,n) 4He occur, as the primary fusion products 3He and T react in flight with thermal deuterons. In implosions with moderate fuel areal density (~ 5–100 mg/cm 2), the secondary D- 3He reaction saturates, while the D-T reaction does not, and the combined information from these secondary products is used to constrain both the areal density and either the plasma electron temperature or changes in the composition due to mix of shell material into the fuel. The underlying theory of this technique is developed and appliedmore » to three classes of implosions on the National Ignition Facility: direct-drive exploding pushers, indirect-drive 1-shock and 2-shock implosions,and polar direct-drive implosions. In the 1- and 2-shock implosions, the electron temperature is inferred to be 0.65 x and 0.33 x the burn-averaged ion temperature, respectively. The inferred mixed mass in the polar direct-drive implosions is in agreement with measurements using alternative techniques.« less

Two-dimensional implosion simulations with a kinetic particle code [2D implosion simulations with a kinetic particle code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagert, Irina; Even, Wesley Paul; Strother, Terrance Timothy

Here, we perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focusmore » on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.« less

Two-dimensional implosion simulations with a kinetic particle code [2D implosion simulations with a kinetic particle code

DOE PAGES

Sagert, Irina; Even, Wesley Paul; Strother, Terrance Timothy

2017-05-17

Here, we perform two-dimensional implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both continuum and rarefied flows. We perform simple two-dimensional disk implosion simulations using one-particle species and compare the results to simulations with the hydrodynamics code rage. The impact of the particle mean free path on the implosion is also explored. In a second study, we focusmore » on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of rage and statistical noise in the kinetic studies.« less

Suppression of laser nonuniformity imprinting using a thin high-z coating.

PubMed

Karasik, Max; Weaver, J L; Aglitskiy, Y; Oh, J; Obenschain, S P

2015-02-27

Imprinting of laser nonuniformity is a limiting factor in direct-drive inertial confinement fusion experiments, particularly when available laser smoothing is limited. A thin (∼400  Å) high-Z metal coating is found to substantially suppress laser imprint for planar targets driven by pulse shapes and intensities relevant to implosions on the National Ignition Facility while retaining low adiabat target acceleration. A hybrid of indirect and direct drive, this configuration results in initial ablation by x rays from the heated high-Z layer, creating a large standoff for perturbation smoothing.

Investigating the effect of adding an on-axis jet to Ar gas puff Z pinches on Z.

DOE PAGES

Harvey-Thompson, Adam James; Jennings, Christopher Ashley; Jones, Brent M.; ...

2016-10-20

Double-shell Ar gas puff implosions driven by 16.5±0.5 MA on the Z generator at Sandia National Laboratories are very effective emitters of Ar K-shell radiation (photon energy >3 keV), producing yields of 330 ± 9% kJ (B. Jones et al., Phys. Plasmas, 22, 020706, 2015). In addition, previous simulations and experiments have reported dramatic increases in K-shell yields when adding an on-axis jet to double shell gas puffs for some configurations.

The NOvA software testing framework

NASA Astrophysics Data System (ADS)

Tamsett, M.; C Group

2015-12-01

The NOvA experiment at Fermilab is a long-baseline neutrino experiment designed to study vε appearance in a vμ beam. NOvA has already produced more than one million Monte Carlo and detector generated files amounting to more than 1 PB in size. This data is divided between a number of parallel streams such as far and near detector beam spills, cosmic ray backgrounds, a number of data-driven triggers and over 20 different Monte Carlo configurations. Each of these data streams must be processed through the appropriate steps of the rapidly evolving, multi-tiered, interdependent NOvA software framework. In total there are greater than 12 individual software tiers, each of which performs a different function and can be configured differently depending on the input stream. In order to regularly test and validate that all of these software stages are working correctly NOvA has designed a powerful, modular testing framework that enables detailed validation and benchmarking to be performed in a fast, efficient and accessible way with minimal expert knowledge. The core of this system is a novel series of python modules which wrap, monitor and handle the underlying C++ software framework and then report the results to a slick front-end web-based interface. This interface utilises modern, cross-platform, visualisation libraries to render the test results in a meaningful way. They are fast and flexible, allowing for the easy addition of new tests and datasets. In total upwards of 14 individual streams are regularly tested amounting to over 70 individual software processes, producing over 25 GB of output files. The rigour enforced through this flexible testing framework enables NOvA to rapidly verify configurations, results and software and thus ensure that data is available for physics analysis in a timely and robust manner.

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE PAGES

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho; ...

2017-05-23

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Fire suppression as a thermal implosion

NASA Astrophysics Data System (ADS)

Novozhilov, Vasily

2017-01-01

The present paper discusses the possibility of the thermal implosion scenario. This process would be a reverse of the well known thermal explosion (autoignition) phenomenon. The mechanism for thermal implosion scenario is proposed which involves quick suppression of the turbulent diffusion flame. Classical concept of the thermal explosion is discussed first. Then a possible scenario for the reverse process (thermal implosion) is discussed and illustrated by a relevant mathematical model. Based on the arguments presented in the paper, thermal implosion may be observed as an unstable equilibrium point on the generalized Semenov diagram for turbulent flame, however this hypothesis requires ultimate experimental confirmation.

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Wellbottom fluid implosion treatment system

DOEpatents

Brieger, Emmet F.

2001-01-01

A system for inducing implosion shock forces on perforation traversing earth formations with fluid pressure where an implosion tool is selected relative to a shut in well pressure and a tubing pressure to have a large and small area piston relationship in a well tool so that at a predetermined tubing pressure the pistons move a sufficient distance to open an implosion valve which permits a sudden release of well fluid pressure into the tubing string and produces an implosion force on the perforations. A pressure gauge on the well tool records tubing pressure and well pressure as a function of time.

Relationship between symmetry and laser pulse shape in low-fill hohlraums at the National Ignition Facility

NASA Astrophysics Data System (ADS)

MacLaren, Steve; Zylstra, A. B.; Yi, A.; Kline, J. L.; Kyrala, G. A.; Kot, L. B.; Loomis, E. N.; Perry, T. S.; Shah, R. C.; Masse, L. P.; Ralph, J. E.; Khan, S. F.

2017-10-01

Typically in indirect-drive inertial confinement fusion (ICF) hohlraums cryogenic helium gas fill is used to impede the motion of the hohlraum wall plasma as it is driven by the laser pulse. A fill of 1 mg/cc He has been used to significantly suppress wall motion in ICF hohlraums at the National Ignition Facility (NIF); however, this level of fill also causes laser-plasma instabilities (LPI) which result in hot electrons, time-dependent symmetry swings and reduction in drive due to increased backscatter. There are currently no adequate models for these phenomena in codes used to simulate integrated ICF experiments. A better compromise is a fill in the range of 0.3 0.6 mg/cc, which has been shown to provide some reduction in wall motion without incurring significant LPI effects. The wall motion in these low-fill hohlraums and the resulting effect on symmetry due to absorption of the inner cone beams by the outer cone plasma can be simulated with some degree of accuracy with the hydrodynamics and inverse Bremsstrahlung models in ICF codes. We describe a series of beryllium capsule implosions in 0.3 mg/cc He fill hohlraums that illustrate the effect of pulse shape on implosion symmetry in the ``low-fill'' regime. In particular, we find the shape of the beginning or ``foot'' of the pulse has significant leverage over the final symmetry of the stagnated implosion. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Weber, C. R.; Milovich, J. L.

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This study describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Finally, for both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Weber, C. R.; Milovich, J. L.

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This paper describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. For both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility

DOE PAGES

Clark, D. S.; Weber, C. R.; Milovich, J. L.; ...

2016-03-14

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensionalmore » (3D) character of the flow, accurately modeling NIF implosions remains at the edge of current simulation capabilities. This study describes the current state of progress of 3D capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Finally, for both implosion types, the simulations show reasonable, though not perfect, agreement with the data and suggest that a reliable predictive capability is developing to guide future implosions toward ignition.« less

In-flight observations of low-mode ρR asymmetries in NIF implosionsa)

NASA Astrophysics Data System (ADS)

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; Rygg, J. R.; Kritcher, A.; Rosenberg, M. J.; Rinderknecht, H. G.; Hicks, D. G.; Friedrich, S.; Bionta, R.; Meezan, N. B.; Olson, R.; Atherton, J.; Barrios, M.; Bell, P.; Benedetti, R.; Berzak Hopkins, L.; Betti, R.; Bradley, D.; Callahan, D.; Casey, D.; Collins, G.; Dewald, E. L.; Dixit, S.; Döppner, T.; Edwards, M. J.; Gatu Johnson, M.; Glenn, S.; Grim, G.; Hatchett, S.; Jones, O.; Khan, S.; Kilkenny, J.; Kline, J.; Knauer, J.; Kyrala, G.; Landen, O.; LePape, S.; Li, C. K.; Lindl, J.; Ma, T.; Mackinnon, A.; Manuel, M. J.-E.; Meyerhofer, D.; Moses, E.; Nagel, S. R.; Nikroo, A.; Parham, T.; Pak, A.; Petrasso, R. D.; Prasad, R.; Ralph, J.; Robey, H. F.; Ross, J. S.; Sangster, T. C.; Sepke, S.; Sinenian, N.; Sio, H. W.; Spears, B.; Tommasini, R.; Town, R.; Weber, S.; Wilson, D.; Yeamans, C.; Zacharias, R.

2015-05-01

Charged-particle spectroscopy is used to assess implosion symmetry in ignition-scale indirect-drive implosions for the first time. Surrogate D3He gas-filled implosions at the National Ignition Facility produce energetic protons via D+3He fusion that are used to measure the implosion areal density (ρR) at the shock-bang time. By using protons produced several hundred ps before the main compression bang, the implosion is diagnosed in-flight at a convergence ratio of 3-5 just prior to peak velocity. This isolates acceleration-phase asymmetry growth. For many surrogate implosions, proton spectrometers placed at the north pole and equator reveal significant asymmetries with amplitudes routinely ≳ 10 % , which are interpreted as ℓ = 2 Legendre modes. With significant expected growth by stagnation, it is likely that these asymmetries would degrade the final implosion performance. X-ray self-emission images at stagnation show asymmetries that are positively correlated with the observed in-flight asymmetries and comparable in magnitude, contradicting growth models; this suggests that the hot-spot shape does not reflect the stagnated shell shape or that significant residual kinetic energy exists at stagnation. More prolate implosions are observed when the laser drive is sustained ("no-coast"), implying a significant time-dependent asymmetry in peak drive.

Isochoric Implosions for Fast Ignition

NASA Astrophysics Data System (ADS)

Clark, Daniel; Tabak, Max

2006-10-01

Various gain models have shown the potentially great advantages of Fast Ignition (FI) Inertial Confinement Fusion (ICF) over its conventional hotspot ignition counterpart. These gain models, however, all assume nearly uniform-density fuel assemblies. By contrast, typical ICF implosions yield hollowed fuel assemblies with a high-density shell of fuel surrounding a low-density, high-pressure hotspot. To realize fully the advantages of FI, then, an alternative implosion design must be found which yields nearly isochoric fuel assemblies without substantial hotspots. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley [Luftfahrtforschung 19, 302 (1942)] may be employed to yield precisely such quasi-isochoric imploded states. The difficulty remains, however, of accessing these self-similarly imploding configurations from initial conditions representing an actual ICF target, namely a uniform, solid-density shell at rest. Furthermore, these specialized implosions must be realized for practicable drive parameters, i.e., accessible peak pressures, shell aspect ratios, etc. An implosion scheme is presented which meets all of these requirements, suggesting the possibility of genuinely isochoric implosions for FI.

Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A., E-mail: abos@lle.rochester.edu; Woo, K. M.; Betti, R.

2015-07-15

The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of χ{sub Ω} ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Woo, K. M.; Nora, R.

2015-07-02

The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIFmore » implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of ΧΩ ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.« less

Symmetry tuning for DIME Campaign

NASA Astrophysics Data System (ADS)

Krasheninnikova, Natalia; Schmitt, Mark; Tregillis, Ian; Bradley, P.; Cobble, J.; Kyrala, G.; Murphy, T.; Obrey, K.; Hsu, S.; Shah, R.; Batha, S.; Craxton, S.; McKenty, P.

2012-10-01

Defect Induced Mix Experiment (DIME) investigates the effects of 4 pi as well as surface feature-driven mix on the directly driven ICF capsule implosion. To minimize the effects of the laser-drive asymmetry, beam pointings, pulse shape, and the energy distribution between the lasers need to be optimized for a particular capsule and shot energy. In support of the DIME experimental campaigns on OMEGA and NIF, symmetry tuning was performed with the rad-hydro code HYDRA. To assess the impact on the symmetry, synthetic radiographs and self-emission images were examined and compared with the experimental results from OMEGA and NIF shots. The dynamics of the capsules imploded under polar direct drive conditions were compared with symmetrically driven ones and the effects of cross-beam transfer and the laser imprinting on the symmetry were also investigated. Work performed by Los Alamos National Laboratory under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy.

A simple method to prevent hard X-ray-induced preheating effects inside the cone tip in indirect-drive fast ignition implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Dongxiao; Shan, Lianqiang; Zhou, Weimin

During fast-ignition implosions, preheating of inside the cone tip caused by hard X-rays can strongly affect the generation and transport of hot electrons in the cone. Although indirect-drive implosions have a higher implosion symmetry, they cause stronger preheating effects than direct-drive implosions. To control the preheating of the cone tip, we propose the use of indirect-drive fast-ignition targets with thicker tips. Experiments carried out at the ShenGuang-III prototype laser facility confirmed that thicker tips are effective for controlling preheating. Moreover, these results were consistent with those of 1D radiation hydrodynamic simulations.

Radio Observations as a Tool to Investigate Shocks and Asymmetries in Accreting White Dwarf Binaries

NASA Astrophysics Data System (ADS)

Weston, Jennifer Helen Seng; E-Nova Project

2017-01-01

In this dissertation, I use radio observations with the Karl G. Jansky Very Large Array (VLA) to reveal that colliding flows within the ejecta from nova explosions can lead to shocks that accelerate particles and produce radio synchrotron emission. In both novae V1723 Aql and V5589 Sgr, radio emission within the first one to two months deviated strongly from the classic thermal model for radio emission from novae. Three years of radio observations of V1723 Aql show that multiple outflows from the system collided to create non-thermal shocks with a brightness temperature of >106 K. After these shocks faded, the radio light curve became roughly consistent with an expanding thermal shell. However, resolved images of V1723 Aql show elongated material that apparently rotates its major axis over the course of 15 months. In the case of nova V5589 Sgr, I show that the early radio emission is dominated by a shock-powered non-thermal flare that produces strong (kTx > 33 keV) X-rays. These findings have important implications for understanding how normal novae generate GeV gamma-rays.Additionally, I present VLA observations of the symbiotic star CH Cyg and two small surveys of symbiotic binaries. Radio observations of CH Cyg tie the ejection of a collimated jet to a change of state in the accretion disk, strengthening the link between bipolar outflows from accreting white dwarfs and other types of accreting compact objects. Next, I use a survey of eleven accretion-driven symbiotic binaries to determine that the radio brightness of a symbiotic system could potentially be used as an indicator of whether it is powered predominantly by shell burning on the surface of the white dwarf or by accretion. This survey also produces the first radio detections of seven of the target systems. In the second survey of seventeen symbiotic binaries, I spatially resolve extended radio emission in several systems for the first time. The results from these surveys provide some support for the model of radio emission where the red giant wind is photoionized by the white dwarf, and suggest that there may be a greater population of radio faint, accretion driven symbiotic systems.

Developing one-dimensional implosions for inertial confinement fusion science

DOE PAGES

Kline, John L.; Yi, Sunghwan A.; Simakov, Andrei Nikolaevich; ...

2016-12-12

Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains. To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where 1D means measured yield overmore » the 1D clean calculation. A high adiabat, low convergence platform is being developed using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However, double shell targets have a different set of trade-off versus advantages. As a result, details for each of these approaches are described.« less

Two-plasmon decay mitigation in direct-drive inertial-confinement-fusion experiments using multilayer targets

DOE PAGES

Follett, R. K.; Delettrez, J. A.; Edgell, D. H.; ...

2016-04-15

Multilayer direct-drive inertial-confinement-fusion (ICF) targets are shown to significantly reduce two-plasmon-decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA Laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor of five reduction in hot-electron generation (> 50 keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD driven hot-electron production using a laser-plasma interaction code (LPSE) that includes nonlinear and kinetic effects show excellent agreement with the measurements. As a result, the simulations suggest that the reduction in hot-electron productionmore » observed in the multilayer targets is primarily due to increased electron-ion collisional damping.« less

High-resolution, detailed simulations of low foot and high foot implosion experiments on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Clark, Daniel

2015-11-01

In order to achieve the several hundred Gbar stagnation pressures necessary for inertial confinement fusion ignition, implosion experiments on the National Ignition Facility (NIF) require the compression of deuterium-tritium fuel layers by a convergence ratio as high as forty. Such high convergence implosions are subject to degradation by a range of perturbations, including the growth of small-scale defects due to hydrodynamic instabilities, as well as longer scale modulations due to radiation flux asymmetries in the enclosing hohlraum. Due to the broad range of scales involved, and also the genuinely three-dimensional (3-D) character of the flow, accurately modeling NIF implosions remains at the edge of current radiation hydrodynamics simulation capabilities. This talk describes the current state of progress of 3-D, high-resolution, capsule-only simulations of NIF implosions aimed at accurately describing the performance of specific NIF experiments. Current simulations include the effects of hohlraum radiation asymmetries, capsule surface defects, the capsule support tent and fill tube, and use a grid resolution shown to be converged in companion two-dimensional simulations. The results of detailed simulations of low foot implosions from the National Ignition Campaign are contrasted against results for more recent high foot implosions. While the simulations suggest that low foot performance was dominated by ablation front instability growth, especially the defect seeded by the capsule support tent, high foot implosions appear to be dominated by hohlraum flux asymmetries, although the support tent still plays a significant role. Most importantly, it is found that a single, standard simulation methodology appears adequate to model both implosion types and gives confidence that such a model can be used to guide future implosion designs toward ignition. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Nonuniformity for rotated beam illumination in directly driven heavy-ion fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Runge, J.; Logan, B.G.

A key issue in heavy-ion beam inertial confinement fusion is target interaction, especially implosion symmetry. In this paper the 2D beam irradiation nonuniformity on the surface of a spherical target is studied. This is a first step to studies of 3D dynamical effects on target implosion. So far non-rotated beams have been studied. Because normal incidence may increase Rayleigh-Taylor instabilities, it has been suggested to rotate beams (to increase average uniformity) and hit the target tangentially. The level of beam irradiation uniformity, beam spill and normal incidence is calculated in this paper. In Mathematica the rotated beams are modeled asmore » an annular integrated Gaussian beam. To simplify the chamber geometry, the illumination scheme is not a 4{pi} system, but the beams are arranged on few polar rings around the target. The position of the beam spot rings is efficiently optimized using the analytical model. The number of rings and beams, rotation radii and widths are studied to optimize uniformity and spilled intensity. The results demonstrate that for a 60-beam system on four rings Peak-To-Valley nonuniformities of under 0.5% are possible.« less

Diagnostics for Magnetically Driven Implosions on the 1-MA MAIZE Facility

NASA Astrophysics Data System (ADS)

Campbell, Paul; Yager-Elorriaga, David; Miller, Stephanie; Woolstrum, Jeff; Jones, Michael; Jordan, Nicholas; Lau, Y. Y.; Gilgenbach, Ronald; McBride, Ryan

2017-10-01

The Michigan Accelerator for Inductive Z-pinch Experiments (MAIZE) is a 3-m-diameter Linear Transformer Driver (LTD) at the University of Michigan which supplies a fast electrical pulse (0-1 MA in 100 ns, for matched loads) to various experimental configurations. In order to better investigate these loads, new diagnostics are being developed. First, an EUV/XUV micro-channel plate pinhole camera and a UV laser imaging system are being implemented to better observe the instability structures that form during implosions. Second, an x-pinch radiography diagnostic is being developed to probe deeper into the plasma loads. Third, Rogowski coils are being developed for enhanced load current measurements. Finally, a bolometry system and photo-conducting diamond (PCD) detectors will be implemented to measure x-ray power and energy. These new systems, combined with the existing twelve-frame laser shadowgraphy, and b-dot current monitors, will be powerful tools for the investigation of imploding z-pinch experiments. This research was supported by the DOE through award DE-SC0012328, Sandia National Laboratories contract DE-NA0003525, the National Science Foundation, and a Nuclear Regulatory Commission new-faculty development Grant. D.Y.E. was supported by an NSF fello.

Visualizing deceleration-phase instabilities in inertial confinement fusion implosions using an "enhanced self-emission" technique at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; Robey, H. F.; Benedetti, L. R.; Berzak Hopkins, L.; Bradley, D. K.; Field, J. E.; Haan, S. W.; Hatarik, R.; Hartouni, E.; Izumi, N.; Johnson, S.; Khan, S.; Lahmann, B.; Landen, O. L.; Le Pape, S.; MacPhee, A. G.; Meezan, N. B.; Milovich, J.; Nagel, S. R.; Nikroo, A.; Pak, A. E.; Petrasso, R.; Remington, B. A.; Rice, N. G.; Springer, P. T.; Stadermann, M.; Widmann, K.; Hsing, W.

2018-05-01

High-mode perturbations and low-mode asymmetries were measured in the deceleration phase of indirectly driven, deuterium gas filled inertial confinement fusion capsule implosions at convergence ratios of 10 to 15, using a new "enhanced emission" technique at the National Ignition Facility [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. In these experiments, a high spatial resolution Kirkpatrick-Baez microscope was used to image the x-ray emission from the inner surface of a high-density-carbon capsule's shell. The use of a high atomic number dopant in the shell enabled time-resolved observations of shell perturbations penetrating into the hot spot. This allowed the effects of the perturbations and asymmetries on degrading neutron yield to be directly measured. In particular, mix induced radiation losses of ˜400 J from the hot spot resulted in a neutron yield reduction of a factor of ˜2. In a subsequent experiment with a significantly increased level of short-mode initial perturbations, shown through the enhanced imaging technique to be highly organized radially, the neutron yield dropped an additional factor of ˜2.

Numerical studies of the use of thin high-Z layers for reducing laser imprint in direct-drive inertial-fusion targets

NASA Astrophysics Data System (ADS)

Bates, Jason; Schmitt, Andrew; Karasik, Max; Obenschain, Steve

2012-10-01

Using the FAST code, we present numerical studies of the effect of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of directly-driven inertial-confinement-fusion (ICF) targets. Previous experimental work on the NIKE Laser Facility at the U.S. Naval Research Laboratory demonstrated that the use of high-Z layers may be efficacious in reducing laser non-uniformities imprinted on the target during the start-up phase of the implosion. Such a reduction is highly desirable in a direct-drive ICF scenario because laser non-uniformities seed hydrodynamic instabilities that can amplify during the implosion process, prevent uniform compression and spoil high gain. One of the main objectives of the present work is to assess the utility of high-Z layers for achieving greater laser uniformity in polar-drive target designs planned for the National Ignition Facility. To address this problem, new numerical routines have recently been incorporated in the FAST code, including an improved radiation-transfer package and a three-dimensional ray-tracing algorithm. We will discuss these topics, and present initial simulation results for high-Z planar-target experiments planned on the NIKE Laser Facility later this year.

Enhancing Understanding of Magnetized High Energy Density Plasmas from Solid Liner Implosions Using Fluid Modeling with Kinetic Closures

NASA Astrophysics Data System (ADS)

Masti, Robert; Srinivasan, Bhuvana; King, Jacob; Stoltz, Peter; Hansen, David; Held, Eric

2017-10-01

Recent results from experiments and simulations of magnetically driven pulsed power liners have explored the role of early-time electrothermal instability in the evolution of the MRT (magneto-Rayleigh-Taylor) instability. Understanding the development of these instabilities can lead to potential stabilization mechanisms; thereby providing a significant role in the success of fusion concepts such as MagLIF (Magnetized Liner Inertial Fusion). For MagLIF the MRT instability is the most detrimental instability toward achieving fusion energy production. Experiments of high-energy density plasmas from wire-array implosions have shown the requirement for more advanced physics modeling than that of ideal magnetohydrodynamics. The overall focus of this project is on using a multi-fluid extended-MHD model with kinetic closures for thermal conductivity, resistivity, and viscosity. The extended-MHD model has been updated to include the SESAME equation-of-state tables and numerical benchmarks with this implementation will be presented. Simulations of MRT growth and evolution for MagLIF-relevant parameters will be presented using this extended-MHD model with the SESAME equation-of-state tables. This work is supported by the Department of Energy Office of Science under Grant Number DE-SC0016515.

Formation, spin-up, and stability of field-reversed configurations

DOE PAGES

Omelchenko, Yuri A.

2015-08-24

Formation, spontaneous spin-up and stability of theta-pinch formed field-reversed configurations are studied self-consistently in three dimensions with a multiscale hybrid model that treats all plasma ions as full-orbit collisional macro-particles and the electrons as a massless quasineutral fluid. The end-to-end hybrid simulations for the first time reveal poloidal profiles of implosion-driven fast toroidal plasma rotation and demonstrate three well-known discharge regimes as a function of experimental parameters: the decaying stable configuration, the tilt unstable configuration and the nonlinear evolution of a fast growing tearing mode.

Prolate-Spheroid (``Rugby-Shaped'') Hohlraum for Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Vandenboomgaerde, M.; Bastian, J.; Casner, A.; Galmiche, D.; Jadaud, J.-P.; Laffite, S.; Liberatore, S.; Malinie, G.; Philippe, F.

2007-08-01

A novel rugby-ball shaped hohlraum is designed in the context of the indirect-drive scheme of inertial-confinement fusion (ICF). Experiments were performed on the OMEGA laser and are the first use of rugby hohlraums for ICF studies. Analysis of experimental data shows that the hohlraum energetics is well understood. We show that the rugby-ball shape exhibits advantages over cylinder, in terms of temperature and of symmetry control of the capsule implosion. Simulations indicate that rugby hohlraum driven targets may be candidates for ignition in a context of early Laser MegaJoule experiments with reduced laser energy.

Review of high convergence implosion experiments with single and double shell targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delamater, N. D.; Watt, R. G.; Varnum, W. S.

2002-01-01

Experiments have been been performed in recent years at the Omega laser studying double shell capsules as an a1 teinative, 11011 cryogenic, path towards ignition at NTF. Double shell capsules designed to mitigate the Au M-band radiation asymmetries, were experimentally found to perform well in both spherical and cylindrical hohlraums, achieving near 1-D (-90 %) clean calculated yield at convergence comparable to that required for NIF ignition. Near-term plans include directly driven double shell experiments at Omega, which eliminates Au M-band radiation as a yield degradation m ec h an i s in.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A., E-mail: hurricane1@llnl.gov; Callahan, D. A.; Casey, D. T.

The “High-Foot” platform manipulates the laser pulse-shape coming from the National Ignition Facility laser to create an indirect drive 3-shock implosion that is significantly more robust against instability growth involving the ablator and also modestly reduces implosion convergence ratio. This strategy gives up on theoretical high-gain in an inertial confinement fusion implosion in order to obtain better control of the implosion and bring experimental performance in-line with calculated performance, yet keeps the absolute capsule performance relatively high. In this paper, we will cover the various experimental and theoretical motivations for the high-foot drive as well as cover the experimental resultsmore » that have come out of the high-foot experimental campaign. At the time of this writing, the high-foot implosion has demonstrated record total deuterium-tritium yields (9.3×10{sup 15}) with low levels of inferred mix, excellent agreement with implosion simulations, fuel energy gains exceeding unity, and evidence for the “bootstrapping” associated with alpha-particle self-heating.« less

Progress in detailed modelling of low foot and high foot implosion experiments on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Clark, D. S.; Weber, C. R.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Kritcher, A. L.; Marinak, M. M.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.

2016-05-01

Several dozen high convergence inertial confinement fusion ignition experiments have now been completed on the National Ignition Facility (NIF). These include both “low foot” experiments from the National Ignition Campaign (NIC) and more recent “high foot” experiments. At the time of the NIC, there were large discrepancies between simulated implosion performance and experimental data. In particular, simulations over predicted neutron yields by up to an order of magnitude, and some experiments showed clear evidence of mixing of ablator material deep into the hot spot that could not be explained at the time. While the agreement between data and simulation improved for high foot implosion experiments, discrepancies nevertheless remain. This paper describes the state of detailed modelling of both low foot and high foot implosions using 1-D, 2-D, and 3-D radiation hydrodynamics simulations with HYDRA. The simulations include a range of effects, in particular, the impact of the plastic membrane used to support the capsule in the hohlraum, as well as low-mode radiation asymmetries tuned to match radiography measurements. The same simulation methodology is applied to low foot NIC implosion experiments and high foot implosions, and shows a qualitatively similar level of agreement for both types of implosions. While comparison with the experimental data remains imperfect, a reasonable level of agreement is emerging and shows a growing understanding of the high-convergence implosions being performed on NIF.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanagawa, T.; Sakagami, H.; Nagatomo, H.

In inertial confinement fusion, the implosion process is important in forming a high-density plasma core. In the case of a fast ignition scheme using a cone-guided target, the fuel target is imploded with a cone inserted. This scheme is advantageous for efficiently heating the imploded fuel core; however, asymmetric implosion is essentially inevitable. Moreover, the effect of cone position and opening angle on implosion also becomes critical. Focusing on these problems, the effect of the asymmetric implosion, the initial position, and the opening angle on the compression rate of the fuel is investigated using a three-dimensional pure hydrodynamic code.

On krypton-doped capsule implosion experiments at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Chen, Hui; Ma, T.; Nora, R.; Barrios, M. A.; Scott, H. A.; Schneider, M. B.; Berzak Hopkins, L.; Casey, D. T.; Hammel, B. A.; Jarrott, L. C.; Landen, O. L.; Patel, P. K.; Rosenberg, M. J.; Spears, B. K.

2017-07-01

This paper presents the spectroscopic aspects of using Krypton as a dopant in NIF capsule implosions through simulation studies and the first set of NIF experiments. Using a combination of 2D hohlraum and 1D capsule simulations with comprehensive spectroscopic modeling, the calculations focused on the effect of dopant concentration on the implosion, and the impact of gradients in the electron density and temperature to the Kr line features and plasma opacity. Experimental data were obtained from three NIF Kr-dopant experiments, performed with varying Kr dopant concentrations between 0.01% and 0.03%. The implosion performance, hotspot images, and detailed Kr spectral analysis are summarized relative to the predictions. Data show that fuel-dopant spectroscopy can serve as a powerful and viable diagnostic for inertial confinement fusion implosions.

Effect of the implosion and demolition of a hospital building on the concentration of fungi in the air.

PubMed

Barreiros, Gloria; Akiti, Tiyomi; Magalhães, Ana Cristina Gouveia; Nouér, Simone A; Nucci, Marcio

2015-12-01

Building renovations increase the concentration of Aspergillus conidia in the air. In 2010, one wing of the hospital building was imploded due to structural problems. To evaluate the impact of building implosion on the concentration of fungi in the air, the demolition was performed in two phases: mechanical demolition of 30 m of the building, followed by implosion of the wing. Patients at high risk for aspergillosis were placed in protected wards. Air sampling was performed during mechanical demolition, on the day of implosion and after implosion. Total and specific fungal concentrations were compared in the different areas and periods of sampling, using the anova test. The incidence of IA in the year before and after implosion was calculated. The mean concentration of Aspergillus increased during mechanical demolition and on the day of implosion. However, in the most protected areas, there was no significant difference in the concentration of fungi. The incidence of invasive aspergillosis (cases per 1000 admissions) was 0.9 in the 12 months before, 0.4 during, and 0.5 in the 12 months after mechanical demolition (P > 0.05). Continuous monitoring of the quality of air and effective infection control measures are important to minimize the impact of building demolition. © 2015 Blackwell Verlag GmbH.

Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

1999-11-01

The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

Cost Modeling and Design of Field-Reversed Configuration Fusion Power Plants

NASA Astrophysics Data System (ADS)

Kirtley, David; Slough, John; Helion Team

2017-10-01

The Inductively Driven Liner (IDL) fusion concept uses the magnetically driven implosion of thin (0.5-1 mm) Aluminum hoops to magnetically compress a merged Field-Reversed Configuration (FRC) plasma to fusion conditions. Both the driver and the target have been studied experimentally and theoretically by researchers at Helion Energy, MSNW, and the University of Washington, demonstrating compression fields greater than 100 T and suitable fusion targets. In the presented study, a notional power plant facility using this approach will be described. In addition, a full cost study based on the LLNL Z-IFE and HYLIFE-II studies, the ARIES Tokamak concept, and RAND power plant studies will be described. Finally, the expected capital costs, development requirements, and LCOE for 50 and 500 MW power plants will be given. This analysis includes core FRC plant scaling, metallic liner recycling, radiation shielding, operations, and facilities capital requirements.

Enhanced electron/fuel-ion equilibration through impurity ions: Studies applicable to NIF and Omega

NASA Astrophysics Data System (ADS)

Petrasso, R. D.; Sio, H.; Kabadi, N.; Lahmann, B.; Simpson, R.; Parker, C.; Frenje, J.; Gatu Johnson, M.; Li, C. K.; Seguin, F. H.; Rinderknecht, H.; Casey, D.; Grabowski, P.; Graziani, F.; Taitano, W.; Le, A.; Chacon, L.; Hoffman, N.; Kagan, G.; Simakov, A.; Zylstra, A.; Rosenberg, M.; Betti, R.; Srinivasan, B.; Mancini, R.

2017-10-01

In shock-driven exploding-pushers, a platform used extensively to study multi-species and kinetic effects, electrons and fuel ions are far out of equilibrium, as reflected by very different temperatures. However, impurity ions, even in small quantities, can couple effectively to the electrons, because of a Z2 dependence, and in turn, impurity ions can then strongly couple to the fuel ions. Through this mechanism, electrons and fuel-ions can equilibrate much faster than they otherwise would. This is a quantitative issue, depending upon the amount and Z of the impurity. For NIF and Omega, we consider the role of this process. Coupled non-linear equations, reflecting the temperatures of the three species, are solved for a range of conditions. Consideration is also given to ablatively driven implosions, since impurities can similarly affect the equilibration. This work was supported in part by DOE/NNSA DE-NA0002949 and DE-NA0002726.

Electrothermal instability growth in magnetically driven pulsed power liners

NASA Astrophysics Data System (ADS)

Peterson, Kyle J.; Sinars, Daniel B.; Yu, Edmund P.; Herrmann, Mark C.; Cuneo, Michael E.; Slutz, Stephen A.; Smith, Ian C.; Atherton, Briggs W.; Knudson, Marcus D.; Nakhleh, Charles

2012-09-01

This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.

A Comparison of Implosive Therapy and Systematic Desensitization in the Treatment of Test Anxiety

ERIC Educational Resources Information Center

Smith, Ronald E.; Nye, S. Lee

1973-01-01

Both Desensitization and implosive therapy resulted in significant decreases in scores on Sarason's Test Anxiety Scale. However, the desensitization group also demonstrated a significant reduction in state anxiety assessed during simulated testing sessions and a significant increase in grade point average, while the implosive therapy group showed…

New and improved CH implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Doeppner, T.; Kritcher, A. L.; Ralph, J. E.; Jarrott, L. C.; Albert, F.; Benedetti, L. R.; Field, J. E.; Goyon, C. S.; Hohenberger, M.; Izumi, N.; Milovich, J. L.; Bachmann, B.; Casey, D. T.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

2017-10-01

Improvements to the hohlraum for CH implosions have resulted in near-record hot spot pressures, 225 Gbar. Implosion symmetry and laser energy coupling are improved by using a hohlraum that, compared to the previous high gas-fill hohlraum, is longer, larger, at lower gas fill density, and is fielded at zero wavelength separation to minimize cross-beam energy transfer. With a capsule at 90% of its original size in this hohlraum, implosion symmetry changes from oblate to prolate, at 33% cone fraction. Simulations highlight improved inner beam propagation as the cause of this symmetry change. These implosions have produced the highest yield for CH ablators at modest power and energy, i.e., 360 TW and 1.4 MJ. Upcoming experiments focus on continued improvement in shape as well as an increase in implosion velocity. Further, results and future plans on an increase in capsule size to improve margin will also be presented. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Ultra High Mode Mix in NIF NIC Implosions

NASA Astrophysics Data System (ADS)

Scott, Robbie; Garbett, Warren

2017-10-01

This work re-examines a sub-set of the low adiabat implosions from the National Ignition Campaign in an effort to better understand potential phenomenological sources of `excess' mix observed experimentally. An extensive effort has been made to match both shock-timing and backlit radiography (Con-A) implosion data in an effort to reproduce the experimental conditions as accurately as possible. Notably a 30% reduction in ablation pressure at peak drive is required to match the experimental data. The reduced ablation pressure required to match the experimental data allows the ablator to decompress, in turn causing the DT ice-ablator interface to go Rayleigh-Taylor unstable early in the implosion acceleration phase. Post-processing the runs with various mix models indicates high-mode mix from the DT ice-ablator interface may penetrate deep into the hotspot. This work offers a potential explanation of why these low-adiabat implosions exhibited significantly higher levels of mix than expected from high-fidelity multi-dimensional simulations. Through this new understanding, a possible route forward for low-adiabat implosions on NIF is suggested.

Addressing Common Technical challenges in Inertial Confinement Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, Donald A.

2016-09-22

The implosion phase for Inertial Confinement Fusion (ICF) occurs from initiation of the drive until just before stagnation. Evolution of the shell and fusion fuel during the implosion phase is affected by the initial conditions of the target, the drive history. Poor performing implosions are a result of the behavior that occurs during the implosion phase such as low mode asymmetries, mixing of the ablator into the fuel, and the hydrodynamic evolution of initial target features and defects such as the shell mounting hardware. The ultimate results of these effects can only be measured at stagnation. However, studying the implosionmore » phase can be effective for understanding and mitigating these effects and for of ultimately improving the performance of ICF implosions. As the ICF program moves towards the 2020 milestone to “determine the efficacy of ignition”, it will be important to understand the physics that occurs during the implosion phase. This will require both focused and integrated experiments. Focused experiments will provide the understanding and the evidence needed to support any determination concerning the efficacy of ignition.« less

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calamy, H.; Hamann, F.; Lassalle, F.

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim ofmore » giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.« less

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

NASA Astrophysics Data System (ADS)

Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J. P.; Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.

2006-01-01

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1μs rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-θ simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

NASA Astrophysics Data System (ADS)

Bose, A.; Betti, R.; Mangino, D.; Woo, K. M.; Patel, D.; Christopherson, A. R.; Gopalaswamy, V.; Mannion, O. M.; Regan, S. P.; Goncharov, V. N.; Edgell, D. H.; Forrest, C. J.; Frenje, J. A.; Gatu Johnson, M.; Yu Glebov, V.; Igumenshchev, I. V.; Knauer, J. P.; Marshall, F. J.; Radha, P. B.; Shah, R.; Stoeckl, C.; Theobald, W.; Sangster, T. C.; Shvarts, D.; Campbell, E. M.

2018-06-01

This paper describes a technique for identifying trends in performance degradation for inertial confinement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA which achieved inferred hot-spot pressures ≈56 ± 7 Gbar [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid-modes. This suggests that in addition to low modes, which can cause a degradation of the stagnation pressure, mid-modes are present which reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. It is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase in the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [Bose et al., Phys. Rev. E 94, 011201(R) (2016)].

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

DOE PAGES

Bose, A.; Betti, R.; Mangino, D.; ...

2018-05-29

This paper describes a technique for identifying trends in performance degradation for inertial con finement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA that achieved inferred hot-spot pressures ≈56 ± 7 Gbar [S. Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid modes. This suggests that in addition to low modes, that can cause amore » degradation of the stagnation pressure, mid modes are present that reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. Finally, it is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase of the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [A. Bose et al., Phys. Rev. E 94, 011201(R) (2016)].« less

Analysis of trends in experimental observables: Reconstruction of the implosion dynamics and implications for fusion yield extrapolation for direct-drive cryogenic targets on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Betti, R.; Mangino, D.

This paper describes a technique for identifying trends in performance degradation for inertial con finement fusion implosion experiments. It is based on reconstruction of the implosion core with a combination of low- and mid-mode asymmetries. This technique was applied to an ensemble of hydro-equivalent deuterium-tritium implosions on OMEGA that achieved inferred hot-spot pressures ≈56 ± 7 Gbar [S. Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. All the experimental observables pertaining to the core could be reconstructed simultaneously with the same combination of low and mid modes. This suggests that in addition to low modes, that can cause amore » degradation of the stagnation pressure, mid modes are present that reduce the size of the neutron and x-ray producing volume. The systematic analysis shows that asymmetries can cause an overestimation of the total areal density in these implosions. Finally, it is also found that an improvement in implosion symmetry resulting from correction of either the systematic mid or low modes would result in an increase of the hot-spot pressure from 56 Gbar to ≈ 80 Gbar and could produce a burning plasma when the implosion core is extrapolated to an equivalent 1.9 MJ symmetric direct illumination [A. Bose et al., Phys. Rev. E 94, 011201(R) (2016)].« less

Improving cryogenic deuterium–tritium implosion performance on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangster, T. C.; Goncharov, V. N.; Betti, R.

2013-05-15

A flexible direct-drive target platform is used to implode cryogenic deuterium–tritium (DT) capsules on the OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)]. The goal of these experiments is to demonstrate ignition hydrodynamically equivalent performance where the laser drive intensity, the implosion velocity, the fuel adiabat, and the in-flight aspect ratio (IFAR) are the same as those for a 1.5-MJ target [Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)] designed to ignite on the National Ignition Facility [Hogan et al., Nucl. Fusion 41, 567 (2001)]. The results from a series of 29 cryogenic DT implosions are presented.more » The implosions were designed to span a broad region of design space to study target performance as a function of shell stability (adiabat) and implosion velocity. Ablation-front perturbation growth appears to limit target performance at high implosion velocities. Target outer-surface defects associated with contaminant gases in the DT fuel are identified as the dominant perturbation source at the ablation surface; performance degradation is confirmed by 2D hydrodynamic simulations that include these defects. A trend in the value of the Lawson criterion [Betti et al., Phys. Plasmas 17, 058102 (2010)] for each of the implosions in adiabat–IFAR space suggests the existence of a stability boundary that leads to ablator mixing into the hot spot for the most ignition-equivalent designs.« less

Improving cryogenic deuterium tritium implosion performance on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangster, T. C.; Goncharov, V. N.; Betti, R.

2013-01-01

A flexible direct-drive target platform is used to implode cryogenic deuterium–tritium (DT) capsules on the OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)]. The goal of these experiments is to demonstrate ignition hydrodynamically equivalent performance where the laser drive intensity, the implosion velocity, the fuel adiabat, and the in-flight aspect ratio (IFAR) are the same as those for a 1.5-MJ target [Goncharov et al., Phys. Rev. Lett. 104, 165001 (2010)] designed to ignite on the National Ignition Facility [Hogan et al., Nucl. Fusion 41, 567 (2001)]. The results from a series of 29 cryogenic DT implosions are presented.more » The implosions were designed to span a broad region of design space to study target performance as a function of shell stability (adiabat) and implosion velocity. Ablation-front perturbation growth appears to limit target performance at high implosion velocities. Target outer-surface defects associated with contaminant gases in the DT fuel are identified as the dominant perturbation source at the ablation surface; performance degradation is confirmed by 2D hydrodynamic simulations that include these defects. A trend in the value of the Lawson criterion [Betti et al., Phys. Plasmas 17, 058102 (2010)] for each of the implosions in adiabat–IFAR space suggests the existence of a stability boundary that leads to ablator mixing into the hot spot for the most ignition-equivalent designs.« less

The High-Foot Implosion Campaign on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hurricane, Omar

2013-10-01

The `High-Foot' platform manipulates the laser pulse-shape coming from the National Ignition Facility (NIF) laser to create an indirect drive 3-shock implosion that is significantly more robust against instability growth involving the ablator and also modestly reduces implosion convergence ratio. This tactic gives up on theoretical high-gain in an inertial confinement fusion implosion in order to obtain better control of the implosion and bring experimental performance in-line with calculated performance, yet keeps the absolute capsule performance relatively high. This approach is generally consistent with the philosophy laid out in a recent international workshop on the topic of ignition science on NIF [``Workshop on the Science of Fusion Ignition on NIF,'' Lawrence Livermore National Laboratory Report, LLNL-TR-570412 (2012). Op cit. V. Gocharov and O.A. Hurricane, ``Panel 3 Report: Implosion Hydrodynamics,'' LLNL-TR-562104 (2012)]. Side benefits our the High-Foot pulse-shape modification appear to be improvements in hohlraum behavior--less wall motion achieved through higher pressure He gas fill and improved inner cone laser beam propagation. Another consequence of the `High-Foot' is a higher fuel adiabat, so there is some relation to direct-drive experiments performed at the Laboratory for Laser Energetics (LLE). In this talk, we will cover the various experimental and theoretical motivations for the High-Foot drive as well as cover the experimental results that have come out of the High-Foot experimental campaign. Most notably, at the time of this writing record DT layer implosion performance with record low levels of inferred mix and excellent agreement with one-dimensional implosion models without the aid of mix models. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

DOE PAGES

Zylstra, A. B.; Frenje, J. A.; Séguin, F. H.; ...

2014-11-03

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D 3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D 3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2x higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was usedmore » to infer the areal density (pR) and the shell center-of-mass radius (R cm) from the downshift of the shock-produced D 3He protons. The observed pR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time ('short-coast'), while longer-coasting implosions have lower pR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (~800 ps) than in the short-coast (~400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time. This result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel pR.« less

Implosion dynamics measurements at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hicks, D. G.; Meezan, N. B.; Dewald, E. L.; Mackinnon, A. J.; Olson, R. E.; Callahan, D. A.; Döppner, T.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Di Nicola, P.; Dixit, S. N.; Dzenitis, E. G.; Eggert, J. E.; Farley, D. R.; Frenje, J. A.; Glenn, S. M.; Glenzer, S. H.; Hamza, A. V.; Heeter, R. F.; Holder, J. P.; Izumi, N.; Kalantar, D. H.; Khan, S. F.; Kline, J. L.; Kroll, J. J.; Kyrala, G. A.; Ma, T.; MacPhee, A. G.; McNaney, J. M.; Moody, J. D.; Moran, M. J.; Nathan, B. R.; Nikroo, A.; Opachich, Y. P.; Petrasso, R. D.; Prasad, R. R.; Ralph, J. E.; Robey, H. F.; Rinderknecht, H. G.; Rygg, J. R.; Salmonson, J. D.; Schneider, M. B.; Simanovskaia, N.; Spears, B. K.; Tommasini, R.; Widmann, K.; Zylstra, A. B.; Collins, G. W.; Landen, O. L.; Kilkenny, J. D.; Hsing, W. W.; MacGowan, B. J.; Atherton, L. J.; Edwards, M. J.

2012-12-01

Measurements have been made of the in-flight dynamics of imploding capsules indirectly driven by laser energies of 1-1.7 MJ at the National Ignition Facility [Miller et al., Nucl. Fusion 44, 228 (2004)]. These experiments were part of the National Ignition Campaign [Landen et al., Phys. Plasmas 18, 051002 (2011)] to iteratively optimize the inputs required to achieve thermonuclear ignition in the laboratory. Using gated or streaked hard x-ray radiography, a suite of ablator performance parameters, including the time-resolved radius, velocity, mass, and thickness, have been determined throughout the acceleration history of surrogate gas-filled implosions. These measurements have been used to establish a dynamically consistent model of the ablative drive history and shell compressibility throughout the implosion trajectory. First results showed that the peak velocity of the original 1.3-MJ Ge-doped polymer (CH) point design using Au hohlraums reached only 75% of the required ignition velocity. Several capsule, hohlraum, and laser pulse changes were then implemented to improve this and other aspects of implosion performance and a dedicated effort was undertaken to test the sensitivity of the ablative drive to the rise time and length of the main laser pulse. Changing to Si rather than Ge-doped inner ablator layers and increasing the pulse length together raised peak velocity to 93% ± 5% of the ignition goal using a 1.5 MJ, 420 TW pulse. Further lengthening the pulse so that the laser remained on until the capsule reached 30% (rather than 60%-70%) of its initial radius, reduced the shell thickness and improved the final fuel ρR on companion shots with a cryogenic hydrogen fuel layer. Improved drive efficiency was observed using U rather than Au hohlraums, which was expected, and by slowing the rise time of laser pulse, which was not. The effect of changing the Si-dopant concentration and distribution, as well as the effect of using a larger initial shell thickness were also examined, both of which indicated that instabilities seeded at the ablation front are a significant source of hydrodynamic mix into the central hot spot. Additionally, a direct test of the surrogacy of cryogenic fuel layered versus gas-filled targets was performed. Together all these measurements have established the fundamental ablative-rocket relationship describing the dependence of implosion velocity on fractional ablator mass remaining. This curve shows a lower-than-expected ablator mass at a given velocity, making the capsule more susceptible to feedthrough of instabilities from the ablation front into the fuel and hot spot. This combination of low velocity and low ablator mass indicates that reaching ignition on the NIF will require >20 μm (˜10%) thicker targets and laser powers at or beyond facility limits.

Implosion dynamics measurements at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hicks, D. G.; Meezan, N. B.; Dewald, E. L.

2012-12-15

Measurements have been made of the in-flight dynamics of imploding capsules indirectly driven by laser energies of 1-1.7 MJ at the National Ignition Facility [Miller et al., Nucl. Fusion 44, 228 (2004)]. These experiments were part of the National Ignition Campaign [Landen et al., Phys. Plasmas 18, 051002 (2011)] to iteratively optimize the inputs required to achieve thermonuclear ignition in the laboratory. Using gated or streaked hard x-ray radiography, a suite of ablator performance parameters, including the time-resolved radius, velocity, mass, and thickness, have been determined throughout the acceleration history of surrogate gas-filled implosions. These measurements have been used tomore » establish a dynamically consistent model of the ablative drive history and shell compressibility throughout the implosion trajectory. First results showed that the peak velocity of the original 1.3-MJ Ge-doped polymer (CH) point design using Au hohlraums reached only 75% of the required ignition velocity. Several capsule, hohlraum, and laser pulse changes were then implemented to improve this and other aspects of implosion performance and a dedicated effort was undertaken to test the sensitivity of the ablative drive to the rise time and length of the main laser pulse. Changing to Si rather than Ge-doped inner ablator layers and increasing the pulse length together raised peak velocity to 93% {+-} 5% of the ignition goal using a 1.5 MJ, 420 TW pulse. Further lengthening the pulse so that the laser remained on until the capsule reached 30% (rather than 60%-70%) of its initial radius, reduced the shell thickness and improved the final fuel {rho}R on companion shots with a cryogenic hydrogen fuel layer. Improved drive efficiency was observed using U rather than Au hohlraums, which was expected, and by slowing the rise time of laser pulse, which was not. The effect of changing the Si-dopant concentration and distribution, as well as the effect of using a larger initial shell thickness were also examined, both of which indicated that instabilities seeded at the ablation front are a significant source of hydrodynamic mix into the central hot spot. Additionally, a direct test of the surrogacy of cryogenic fuel layered versus gas-filled targets was performed. Together all these measurements have established the fundamental ablative-rocket relationship describing the dependence of implosion velocity on fractional ablator mass remaining. This curve shows a lower-than-expected ablator mass at a given velocity, making the capsule more susceptible to feedthrough of instabilities from the ablation front into the fuel and hot spot. This combination of low velocity and low ablator mass indicates that reaching ignition on the NIF will require >20 {mu}m ({approx}10%) thicker targets and laser powers at or beyond facility limits.« less

Core conditions for alpha heating attained in direct-drive inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, A.; Woo, K. M.; Betti, R.

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,more » 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.« less

Core conditions for alpha heating attained in direct-drive inertial confinement fusion

DOE PAGES

Bose, A.; Woo, K. M.; Betti, R.; ...

2016-07-07

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,more » 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.« less

X-pinch dynamics: Neck formation and implosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I.; National Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk 634050; Chaikovsky, S. A.

2014-10-15

We propose a model that describes the neck formation and implosion in an X-pinch. The process is simulated to go in two stages. The first stage is neck formation. This stage begins with an electrical explosion of the wires forming the X-pinch, and at the end of the stage, a micropinch (neck) is formed in the region where the wires are crossed. The second stage is neck implosion. The implosion is accompanied by outflow of matter from the neck region, resulting in the formation of a “hot spot”. Analytical estimates obtained in the study under consideration indicate that these stagesmore » are approximately equal in duration. Having analyzed the neck implosion dynamics, we have verified a scaling which makes it possible to explain the observed dependences of the time of occurrence of an x-ray pulse on the X-pinch current and mass.« less

Beryllium implosion experiments at high case-to-capsule ratio on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Zylstra, Alex; Yi, Austin; Kline, John; Kyrala, George; Loomis, Eric; Perry, Ted; Shah, Rahul; Batha, Steve; MacLaren, Steve; Ralph, Joe; Salmonson, Jay; Masse, Laurent; Nikroo, Abbas; Stadermann, Michael; Callahan, Debbie; Hurricane, Omar; Rice, Neal; Huang, Haibo; Kong, Casey

2017-10-01

Using beryllium as an ablator material has several potential advantages for inertial fusion because of its low opacity and thus higher ablation rate. This could enable novel designs taking advantage of the reduced ablation-front growth rate, or operating at lower radiation temperature. To investigate the integrated performance of beryllium implosions, we conducted a tuning campaign leading into DT layered implosions using a 900um radius capsule in a 6.72mm diameter hohlraum (case-to-capsule ratio CCR=3.7); the large CCR enables direct study of the 1-D implosion performance. The tuning campaign shots demonstrate excellent control over the shock timing and implosion symmetry at this CCR. Performance data from the DT experiments will also be discussed. This work was performed under the auspices of the U.S. DoE by LANL under contract DE-AC52-06NA52396.

Core conditions for alpha heating attained in direct-drive inertial confinement fusion.

PubMed

Bose, A; Woo, K M; Betti, R; Campbell, E M; Mangino, D; Christopherson, A R; McCrory, R L; Nora, R; Regan, S P; Goncharov, V N; Sangster, T C; Forrest, C J; Frenje, J; Gatu Johnson, M; Glebov, V Yu; Knauer, J P; Marshall, F J; Stoeckl, C; Theobald, W

2016-07-01

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.

Do At-Risk Students Benefit When NovaNET Is Used for Credit Recovery?

ERIC Educational Resources Information Center

Volkerding, Rebecca Lynn

2012-01-01

The purpose of this study was to determine if it is effective and appropriate to place all students needing credit recovery in computer-based classes regardless of age, risk ratio, and their previous failing grade. Driven by the NCLB mandate for schools to produce greater gains and graduate all students in 4.5 years, districts are now using online…

LLE Review 116 (July-September 2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marozas, J.A., editor

2010-03-12

This issue has the following articles: (1) Optimizing Electron-Positron Pair Production on kJ-Class High-Intensity Lasers for the Purpose of Pair-Plasma Creation; (2) Neutron Yield Study of Direct-Drive, Low-Adiabat Cryogenic D2 Implosions on OMEGA; (3) Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil; (4) A Measurable Lawson Criterion and Hydro-Equivalent Curves for Inertial Confinement Fusion; (5) Pulsed-THz Characterization of Hg-Based, High-Temperature Superconductors; (6) LLE's Summer High School Research Program; (7) FY08 Laser Facility Report; and (8) National Laser Users Facility and External Users Programs.

The physics basis for ignition using indirect-drive targets on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Lindl, John D.; Amendt, Peter; Berger, Richard L.; Glendinning, S. Gail; Glenzer, Siegfried H.; Haan, Steven W.; Kauffman, Robert L.; Landen, Otto L.; Suter, Laurence J.

2004-02-01

The 1990 National Academy of Science final report of its review of the Inertial Confinement Fusion Program recommended completion of a series of target physics objectives on the 10-beam Nova laser at the Lawrence Livermore National Laboratory as the highest-priority prerequisite for proceeding with construction of an ignition-scale laser facility, now called the National Ignition Facility (NIF). These objectives were chosen to demonstrate that there was sufficient understanding of the physics of ignition targets that the laser requirements for laboratory ignition could be accurately specified. This research on Nova, as well as additional research on the Omega laser at the University of Rochester, is the subject of this review. The objectives of the U.S. indirect-drive target physics program have been to experimentally demonstrate and predictively model hohlraum characteristics, as well as capsule performance in targets that have been scaled in key physics variables from NIF targets. To address the hohlraum and hydrodynamic constraints on indirect-drive ignition, the target physics program was divided into the Hohlraum and Laser-Plasma Physics (HLP) program and the Hydrodynamically Equivalent Physics (HEP) program. The HLP program addresses laser-plasma coupling, x-ray generation and transport, and the development of energy-efficient hohlraums that provide the appropriate spectral, temporal, and spatial x-ray drive. The HEP experiments address the issues of hydrodynamic instability and mix, as well as the effects of flux asymmetry on capsules that are scaled as closely as possible to ignition capsules (hydrodynamic equivalence). The HEP program also addresses other capsule physics issues associated with ignition, such as energy gain and energy loss to the fuel during implosion in the absence of alpha-particle deposition. The results from the Nova and Omega experiments approach the NIF requirements for most of the important ignition capsule parameters, including drive temperature, drive symmetry, and hydrodynamic instability. This paper starts with a review of the NIF target designs that have formed the motivation for the goals of the target physics program. Following that are theoretical and experimental results from Nova and Omega relevant to the requirements of those targets. Some elements of this work were covered in a 1995 review of indirect-drive [J. D. Lindl, ``Development of the indirect-drive approach to inertial confinement fusion and the target physics basis for ignition and gain,'' Phys. Plasmas 2, 3933 (1995)]. In order to present as complete a picture as possible of the research that has been carried out on indirect drive, key elements of that earlier review are also covered here, along with a review of work carried out since 1995.

Three-dimensional hydrodynamic simulations of OMEGA implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; Campbell, E. M.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Marshall, F. J.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Stoeckl, C.; Schmitt, A. J.; Obenschain, S.

2017-05-01

The effects of large-scale (with Legendre modes ≲ 10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets ( ˜10 to 20 μm), beam-power imbalance ( σrms˜10 %), and variations ( ˜5 %) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosion targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ˜1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh-Taylor growth.

Pressure signature and evaluation of hammer pulses during underwater implosion in confining environments.

PubMed

Gupta, Sachin; Matos, Helio; Shukla, Arun; LeBlanc, James M

2016-08-01

The fluid structure interaction phenomenon occurring in confined implosions is investigated using high-speed three-dimensional digital image correlation (DIC) experiments. Aluminum tubular specimens are placed inside a confining cylindrical structure that is partially open to a pressurized environment. These specimens are hydrostatically loaded until they naturally implode. The implosion event is viewed, and recorded, through an acrylic window on the confining structure. The velocities captured through DIC are synchronized with the pressure histories to understand the effects of confining environment on the implosion process. Experiments show that collapse of the implodable volume inside the confining tube leads to strong oscillating water hammer waves. The study also reveals that the increasing collapse pressure leads to faster implosions. Both peak and average structural velocities increase linearly with increasing collapse pressure. The effects of the confining environment are better seen in relatively lower collapse pressure implosion experiments in which a long deceleration phase is observed following the peak velocity until wall contact initiates. Additionally, the behavior of the confining environment can be viewed and understood through classical water hammer theory. A one-degree-of-freedom theoretical model was created to predict the impulse pressure history for the particular problem studied.

Higher velocity, high-foot implosions on the National Ignition Facility laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.

By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.« less

Higher velocity, high-foot implosions on the National Ignition Facility laser

DOE PAGES

Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.; ...

2015-05-15

By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.« less

Increase in the energy density of the pinch plasma in 3D implosion of quasi-spherical wire arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V., E-mail: alexvv@triniti.ru; Gasilov, V. A.; Grabovski, E. V.

Results are presented from experimental studies of the characteristics of the soft X-ray (SXR) source formed in the implosion of quasi-spherical arrays made of tungsten wires and metalized kapron fibers. The experiments were carried out at the Angara-5-1 facility at currents of up to 3 MA. Analysis of the spatial distribution of hard X-ray emission with photon energies above 20 keV in the pinch images taken during the implosion of quasi-spherical tungsten wire arrays (QTWAs) showed that a compact quasi-spherical plasma object symmetric with respect to the array axis formed in the central region of the array. Using a diffractionmore » grazing incidence spectrograph, spectra of SXR emission with wavelengths of 20–400 Å from the central, axial, and peripheral regions of the emission source were measured with spatial resolutions along the array radius and height in the implosion of QTWAs. It is shown that the emission spectra of the SXR sources formed under the implosion of quasi-spherical and cylindrical tungsten wire arrays at currents of up to 3 MA have a maximum in the wavelength range of 50–150 Å. It is found that, during the implosion of a QTWA with a profiled linear mass, a redistribution of energy in the emission spectrum takes place, which indicates that, during 3D implosion, the energy of longitudinal motion of the array material additionally contributes to the radiation energy. It is also found that, at close masses of the arrays and close values of the current in the range of 2.4{sup −3} MA, the average energy density in the emission source formed during the implosion of a quasi-spherical wire array is larger by a factor of 7 than in the source formed during the implosion of a cylindrical wire array. The experimental data were compared with results of 3D simulations of plasma dynamics and radiation generation during the implosion of quasi-spherical wire arrays with a profiled mass by using the MARPLE-3D radiative magnetohydrodynamic code, developed at the Keldysh Institute of Applied Mathematics, Russian Academy of Sciences.« less

Robust spherical direct-drive design for NI

NASA Astrophysics Data System (ADS)

Masse, Laurent; Hurricane, O.; Michel, P.; Nora, R.; Tabak, M.; Lawrence Livermore Natl Lab Team

2016-10-01

Achieving ignition in a direct-drive or indirect-drive cryogenic implosion is a tremendous challenge. Both approaches need to deal with physic and technologic issues. During the past years, the indirect drive effort on the National Ignition Facility (NIF) has revealed unpredicted lost of performances that force to think to more robust designs and to dig into detailed physics aspects. Encouraging results have been obtained using a strong first shock during the implosion of CH ablator ignition capsules. These ``high-foot'' implosion results in a significantly lower ablation Rayleigh-Taylor instability growth than that of the NIC point design capsule. The trade-off with this design is a higher fuel adiabat that limits both fuel compression and theoretical capsule yield. The purpose of designing this capsule is to recover a more ideal one-dimensional implosion that is in closer agreement to simulation predictions. In the same spirit of spending energy on margin, at the coast of decreased performance, we are presenting here a study on ``robust'' spherical direct drive design for NIF. This 2-Shock direct drive pulse shape results in a high adiabat (>3) and low convergence (<17) implosion designed to produce a near 1D-like implosion. We take a particular attention to design a robust implosion with respect to long-wavelength non uniformity seeded by power imbalance and target offset. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

Increased nuclear energy yields from the fast implosion of cold shells driven by nonlinear laser plasma interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hora, H.

1976-02-01

The nonlinear interaction force between intense laser fields and cold plasma shells efficiently transforms radiant energy into mechanical energy of implosion. This transfer of energy has been considered before in numerical experiments and it is treated here analytically in a didactic example starting with an inhomogeneous Rayleigh density profile. Up to 50% of the laser energy can be transformed into the energy of compression if a single ''untailored'' pulse of 2.5 x 10/sup 16/ W/cm/sup 2/ intensity and of only a few picosecond duration is used for spherical illumination of a shell. If the pulse is short enough to reducemore » collisional thermalization, then the collapse and compression of the plasma can remain at the threshold of Fermi degeneracy and still be adiabatic. This results in nuclear reaction gains G, based on the deposited energy, E/sub 0/, and without ..cap alpha..-particle reheating, of G=400 for E/sub 0/=2.25 kJ ((D--T reaction), 900 kJ (D--D), 13 MJ (H--B). About 1000 times less laser energy is necessary than in the case of gas dynamic ablation resulting in the same nuclear reaction yields. (AIP)« less

A Computational Study of Re-emission Balls Proposed for the NIF Ignition Symmetry Campaign

NASA Astrophysics Data System (ADS)

Meeker, D. J.; Amendt, P.; Dewald, E.; Edwards, M. J.; Milovich, J.; Suter, L.

2006-10-01

Re-emission balls are high-Z spheres used as surrogates for ICF ignition capsules to detect and correct early-time asymmetries of radiation flux at the target. Emission from these balls mimics the incoming flux due to their high albedo, providing a useful symmetry diagnostic. Experiments on Nova by LANL [1] and LLNL used bismuth (Bi) as the surrogate, selected for its high albedo and insensitivity to the fluorescence of the gold hohlraum wall. We are studying the applicability of these capsules to the NIF symmetry campaign as a potential tuning mechanism to achieve the accuracies required for symmetric implosions. We will describe 2-D simulations that predict the emission of the Bi ball as a function of time, frequency, and spatial distribution, as well as quantifying surrogacy of re- emission balls. Using several tuning examples, we will show the resolution expected from this diagnostic. Suggestions for extending this technique to longer times will be discussed as well as describing 3-D effects from diagnostic viewing ports and an opposing hole to eliminate competing wall emission. [1] Delamater, Phys. Rev. E 53, 5240 (1996), Magelssen, Phys. Rev. E 57, 4663 (1998)

Investigation of the cylindrical vacuum hohlraum energy in the first implosion experiment at the SGIII laser facility

NASA Astrophysics Data System (ADS)

Zhang, Huasen; Jiang, Wei; Ge, Fengjun; Song, Peng; Zou, Shiyang; Huang, Tianxuan; Li, Sanwei; Yang, Dong; Li, Zhichao; Hou, Lifei; Guo, Liang; Che, Xingsen; Du, Huabing; Xie, Xufei; He, Xiaoan; Li, Chaoguang; Zha, Weiyi; Xu, Tao; Liu, Yonggang; Wei, Huiyue; Liu, Xiangming; Chen, Zhongjing; Zhang, Xing; Yan, Ji; Pu, Yudong; Peng, Xiaoshi; Li, Yulong; Gu, Peijun; Zheng, Wudi; Liu, Jie; Ding, Yongkun; Zhu, Shaoping

2018-02-01

The cylindrical vacuum hohlraum energy at the SGIII laser facility [X. T. He and W. Y. Zhang, Eur. Phys. J. D 44, 227 (2007) and W. Zheng et al., High Power Laser Sci. Eng. 4, e21 (2016)] is investigated for the first time. The hohlraum size and the laser energy are intermediate between the Nova and NIF typical hohlraum experiments. It is found that the SGIII hohlraum exhibits an x-ray conversion efficiency of about 85%, which is more close to that of the NIF hohlraum. The LARED simulations of the SGIII hohlraum underestimate about 15% of the radiation flux measured from the laser entrance hole, while the capsule radiation drive inferred from the x-ray bangtime is roughly consistent with the experiments. The underestimation of the SGIII hohlraum radiation flux is mainly caused by the more enclosed laser entrance hole in the LARED simulation. The comparison between the SGIII and NIF hohlraum simulations by LARED indicates that the LARED generally underestimates the measured radiation flux by 15% for the high x-ray conversion efficiency hohlraums, while it can roughly predict the capsule radiation drive inside the hohlraum.

Gamma-ray emission from internal shocks in novae

NASA Astrophysics Data System (ADS)

Martin, P.; Dubus, G.; Jean, P.; Tatischeff, V.; Dosne, C.

2018-04-01

Context. Gamma-ray emission at energies ≥100 MeV has been detected from nine novae using the Fermi Large Area Telescope (LAT), and can be explained by particle acceleration at shocks in these systems. Eight out of these nine objects are classical novae in which interaction of the ejecta with a tenuous circumbinary material is not expected to generate detectable gamma-ray emission. Aim. We examine whether particle acceleration at internal shocks can account for the gamma-ray emission from these novae. The shocks result from the interaction of a fast wind radiatively-driven by nuclear burning on the white dwarf with material ejected in the initial runaway stage of the nova outburst. Methods: We present a one-dimensional model for the dynamics of a forward and reverse shock system in a nova ejecta, and for the associated time-dependent particle acceleration and high-energy gamma-ray emission. Non-thermal proton and electron spectra are calculated by solving a time-dependent transport equation for particle injection, acceleration, losses, and escape from the shock region. The predicted emission is compared to LAT observations of V407 Cyg, V1324 Sco, V959 Mon, V339 Del, V1369 Cen, and V5668 Sgr. Results: The ≥100 MeV gamma-ray emission arises predominantly from particles accelerated up to 100 GeV at the reverse shock and undergoing hadronic interactions in the dense cooling layer downstream of the shock. The emission rises within days after the onset of the wind, quickly reaches a maximum, and its subsequent decrease reflects mostly the time evolution of the wind properties. Comparison to gamma-ray data points to a typical scenario where an ejecta of mass 10-5-10-4 M⊙ expands in a homologous way with a maximum velocity of 1000-2000 km s-1, followed within a day by a wind with a velocity <2000 km s-1 and a mass-loss rate of 10-4-10-3 M⊙ yr-1 declining over a time scale of a few days. Because of the large uncertainties in the measurements, many parameters of the problem are degenerate and/or poorly constrained except for the wind velocity, the relatively low values of which result in the majority of best-fit models having gamma-ray spectra with a high-energy turnover below 10 GeV. Our typical model is able to account for the main features in the observations of the recent gamma-ray nova ASASSN-16ma. Conclusions: The internal shock model can account for the gamma-ray emission of the novae detected by Fermi LAT. Gamma-ray observations hold potential for probing the mechanism of mass ejection in novae, but should be combined to diagnostics of the thermal emission at lower energies to be more constraining.

Simulations of fill tube effects on the implosion of high-foot NIF ignition capsules

NASA Astrophysics Data System (ADS)

Dittrich, T. R.; Hurricane, O. A.; Berzak-Hopkins, L. F.; Callahan, D. A.; Casey, D. T.; Clark, D.; Dewald, E. L.; Doeppner, T.; Haan, S. W.; Hammel, B. A.; Harte, J. A.; Hinkel, D. E.; Kozioziemski, B. J.; Kritcher, A. L.; Ma, T.; Nikroo, A.; Pak, A. E.; Parham, T. G.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Salmonson, J. D.; Springer, P. T.; Weber, C. R.; Zimmerman, G. B.; Kline, J. L.

2016-05-01

Encouraging results have been obtained using a strong first shock during the implosion of carbon-based ablator ignition capsules. These “high-foot” implosion results show that capsule performance deviates from 1D expectations as laser power and energy are increased. A possible cause of this deviation is the disruption of the hot spot by jets originating in the capsule fill tube. Nominally, a 10 μm outside diameter glass (SiO2) fill tube is used in these implosions. Simulations indicate that a thin coating of Au on this glass tube may lessen the hotspot disruption. These results and other mitigation strategies will be presented.

Scaling laws for ignition at the National Ignition Facility from first principles.

PubMed

Cheng, Baolian; Kwan, Thomas J T; Wang, Yi-Ming; Batha, Steven H

2013-10-01

We have developed an analytical physics model from fundamental physics principles and used the reduced one-dimensional model to derive a thermonuclear ignition criterion and implosion energy scaling laws applicable to inertial confinement fusion capsules. The scaling laws relate the fuel pressure and the minimum implosion energy required for ignition to the peak implosion velocity and the equation of state of the pusher and the hot fuel. When a specific low-entropy adiabat path is used for the cold fuel, our scaling laws recover the ignition threshold factor dependence on the implosion velocity, but when a high-entropy adiabat path is chosen, the model agrees with recent measurements.

Capsule Ablator Inflight Performance Measurements Via Streaked Radiography Of ICF Implosions On The NIF*

NASA Astrophysics Data System (ADS)

Dewald, E. L.; Tommasini, R.; Mackinnon, A.; MacPhee, A.; Meezan, N.; Olson, R.; Hicks, D.; LePape, S.; Izumi, N.; Fournier, K.; Barrios, M. A.; Ross, S.; Pak, A.; Döppner, T.; Kalantar, D.; Opachich, K.; Rygg, R.; Bradley, D.; Bell, P.; Hamza, A.; Dzenitis, B.; Landen, O. L.; MacGowan, B.; LaFortune, K.; Widmayer, C.; Van Wonterghem, B.; Kilkenny, J.; Edwards, M. J.; Atherton, J.; Moses, E. I.

2016-03-01

Streaked 1-dimensional (slit imaging) radiography of 1.1 mm radius capsules in ignition hohlraums was recently introduced on the National Ignition Facility (NIF) and gives an inflight continuous record of capsule ablator implosion velocities, shell thickness and remaining mass in the last 3-5 ns before peak implosion time. The high quality data delivers good accuracy in implosion metrics that meets our requirements for ignition and agrees with recently introduced 2-dimensional pinhole radiography. Calculations match measured trajectory across various capsule designs and laser drives when the peak laser power is reduced by 20%. Furthermore, calculations matching measured trajectories give also good agreement in ablator shell thickness and remaining mass.

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility

DOE PAGES

Olson, R. E.; Leeper, R. J.; Kline, J. L.; ...

2016-12-07

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D 2 and DT layer Inertial Confinement Fusion (ICF) implosions that can access low-to-moderate hot spot convergence ratio (1230) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CR’s of 12-17, and the hot spot formation is well understood, demonstratedmore » by good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.« less

The Defect Induced Mix Experiment (DIME) for NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmitt, Mark J; Bradley, Paul A; Cobble, James A

2012-06-18

LANL will perform two Defect Induced Mix Experiment (DIME) implosion campaigns on NIF in July and September, 2012. This presentation describes the goals for these shots and the experimental configuration and diagnostic set up to collect the appropriate data. The first two-shot campaign will focus on executing polar direct drive (PDD) implosions of plastic CH capsules filled with deuterium gas. Gas filling will be performed through a fill tube at target chamber center. A vanadium backligher foil will provide x-rays to radiograph the last half of the implosion to compare the implosion trajectory with modeling predictions. An equatorial groove inmore » one of the capsules will be present to determine its effect on implosion dynamics. The second DIME campaign will commission and use a spectral imager (MMI) to examine the evolution of thin capsule layers doped with either Ge or Ga at 1.85%. Spectral line emission from these layers will quantify the mix width at the inner shell radius and near an equatorial groove feature.« less

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Olson, R. E.; Leeper, R. J.; Kline, J. L.; Zylstra, A. B.; Yi, S. A.; Biener, J.; Braun, T.; Kozioziemski, B. J.; Sater, J. D.; Bradley, P. A.; Peterson, R. R.; Haines, B. M.; Yin, L.; Berzak Hopkins, L. F.; Meezan, N. B.; Walters, C.; Biener, M. M.; Kong, C.; Crippen, J. W.; Kyrala, G. A.; Shah, R. C.; Herrmann, H. W.; Wilson, D. C.; Hamza, A. V.; Nikroo, A.; Batha, S. H.

2016-12-01

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D2 and DT layer inertial confinement fusion (ICF) implosions that can access a low-to-moderate hot-spot convergence ratio (12 30 ) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CRs of 12-17, and the hot-spot formation is well understood, demonstrated by a good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

2D Implosion Simulations with a Kinetic Particle Code

NASA Astrophysics Data System (ADS)

Sagert, Irina; Even, Wesley; Strother, Terrance

2017-10-01

Many problems in laboratory and plasma physics are subject to flows that move between the continuum and the kinetic regime. We discuss two-dimensional (2D) implosion simulations that were performed using a Monte Carlo kinetic particle code. The application of kinetic transport theory is motivated, in part, by the occurrence of non-equilibrium effects in inertial confinement fusion (ICF) capsule implosions, which cannot be fully captured by hydrodynamics simulations. Kinetic methods, on the other hand, are able to describe both, continuum and rarefied flows. We perform simple 2D disk implosion simulations using one particle species and compare the results to simulations with the hydrodynamics code RAGE. The impact of the particle mean-free-path on the implosion is also explored. In a second study, we focus on the formation of fluid instabilities from induced perturbations. I.S. acknowledges support through the Director's fellowship from Los Alamos National Laboratory. This research used resources provided by the LANL Institutional Computing Program.

Fuel gain exceeding unity in an inertially confined fusion implosion.

PubMed

Hurricane, O A; Callahan, D A; Casey, D T; Celliers, P M; Cerjan, C; Dewald, E L; Dittrich, T R; Döppner, T; Hinkel, D E; Berzak Hopkins, L F; Kline, J L; Le Pape, S; Ma, T; MacPhee, A G; Milovich, J L; Pak, A; Park, H-S; Patel, P K; Remington, B A; Salmonson, J D; Springer, P T; Tommasini, R

2014-02-20

Ignition is needed to make fusion energy a viable alternative energy source, but has yet to be achieved. A key step on the way to ignition is to have the energy generated through fusion reactions in an inertially confined fusion plasma exceed the amount of energy deposited into the deuterium-tritium fusion fuel and hotspot during the implosion process, resulting in a fuel gain greater than unity. Here we report the achievement of fusion fuel gains exceeding unity on the US National Ignition Facility using a 'high-foot' implosion method, which is a manipulation of the laser pulse shape in a way that reduces instability in the implosion. These experiments show an order-of-magnitude improvement in yield performance over past deuterium-tritium implosion experiments. We also see a significant contribution to the yield from α-particle self-heating and evidence for the 'bootstrapping' required to accelerate the deuterium-tritium fusion burn to eventually 'run away' and ignite.

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility.

PubMed

Olson, R E; Leeper, R J; Kline, J L; Zylstra, A B; Yi, S A; Biener, J; Braun, T; Kozioziemski, B J; Sater, J D; Bradley, P A; Peterson, R R; Haines, B M; Yin, L; Berzak Hopkins, L F; Meezan, N B; Walters, C; Biener, M M; Kong, C; Crippen, J W; Kyrala, G A; Shah, R C; Herrmann, H W; Wilson, D C; Hamza, A V; Nikroo, A; Batha, S H

2016-12-09

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D_{2} and DT layer inertial confinement fusion (ICF) implosions that can access a low-to-moderate hot-spot convergence ratio (1230) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CRs of 12-17, and the hot-spot formation is well understood, demonstrated by a good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

Theory of hydro-equivalent ignition for inertial fusion and its applications to OMEGA and the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nora, R.; Betti, R.; Bose, A.

The theory of ignition for inertial confinement fusion capsules [R. Betti et al., Phys. Plasmas 17, 058102 (2010)] is used to assess the performance requirements for cryogenic implosion experiments on the Omega Laser Facility. The theory of hydrodynamic similarity is developed in both one and two dimensions and tested using multimode hydrodynamic simulations with the hydrocode DRACO [P. B. Radha et al., Phys. Plasmas 12, 032702 (2005)] of hydro-equivalent implosions (implosions with the same implosion velocity, adiabat, and laser intensity). The theory is used to scale the performance of direct-drive OMEGA implosions to the National Ignition Facility (NIF) energy scalesmore » and determine the requirements for demonstrating hydro-equivalent ignition on OMEGA. Hydro-equivalent ignition on OMEGA is represented by a cryogenic implosion that would scale to ignition on the NIF at 1.8 MJ of laser energy symmetrically illuminating the target. It is found that a reasonable combination of neutron yield and areal density for OMEGA hydro-equivalent ignition is 3 to 6 × 10{sup 13} and ∼0.3 g/cm{sup 2}, respectively, depending on the level of laser imprinting. This performance has not yet been achieved on OMEGA.« less

Three-Dimensional Hydrodynamic Simulations of the Effects of Laser Imprint in OMEGA Implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Campbell, E. M.; Goncharov, V. N.; Regan, S. P.; Shvydky, A.; Schmitt, A. J.

2017-10-01

Illumination of direct-drive implosion targets by the OMEGA laser introduces large-amplitude broadband modulations in the absorbed energy from the largest (target size 900- μm) to smallest (speckle size 2- μm) spatial scales. These modulations ``imprint'' perturbations into a target that are amplified because of the secular and Rayleigh-Taylor growths during acceleration and deceleration of the target. The degradation of performance of room-temperature and cryogenic OMEGA implosions caused by these perturbations were simulated in three dimensions using the code ASTER. The highest-resolution simulations resolve perturbation modes as high as l 200 . The high modes l 50to 100 dominate in the perturbation spectrum during the linear growth, while the late-time nonlinear evolution results in domination of modes with l 30to 50 . Smoothing by spectral dispersion reduces the linear-phase mode amplitudes by a factor of 4 and results in substantial improvements in implosion performance that is in good agreement with measurements. The effects of imprint on implosion performance are compared with the effects of other implosion asymmetries, such as those induced because of laser beam imbalance, mistiming and mispointing, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Effects of local defect growth in direct-drive cryogenic implosions on OMEGA

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Goncharov, V. N.; Shmayda, W. T.; Harding, D. R.; Sangster, T. C.; Meyerhofer, D. D.

2013-08-01

Spherically symmetric, low-adiabat (adiabat α ≲ 3) cryogenic direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1995)] yield less than 10% of the neutrons predicted in one-dimensional hydrodynamic simulations. Two-dimensional hydrodynamic simulations suggest that this performance degradation can be explained assuming perturbations from isolated defects of submicron to tens-of-micron scale on the outer surface or inside the shell of implosion targets. These defects develop during the cryogenic filling process and typically number from several tens up to hundreds for each target covering from about 0.2% to 1% of its surface. The simulations predict that such defects can significantly perturb the implosion and result in the injection of about 1 to 2 μg of the hot ablator (carbon-deuterium) and fuel (deuterium-tritium) materials from the ablation surface into the targets. Both the hot mass injection and perturbations of the shell reduce the final shell convergence ratio and implosion performance. The injected carbon ions radiatively cool the hot spot, reducing the fuel temperature, and further reducing the neutron yield. The negative effect of local defects can be minimized by decreasing the number and size of these defects and/or using more hydrodynamically stable implosion designs with higher shell adiabat.

Wavelength Detuning Cross-Beam Energy Transfer Mitigation Scheme for Direct-Drive: Modeling and Evidence from National Ignition Facility Implosions

NASA Astrophysics Data System (ADS)

Marozas, J. A.

2017-10-01

Cross-beam energy transfer (CBET) has been shown to significantly reduce the laser absorption and implosion speed in direct-drive implosion experiments on OMEGA and the National Ignition Facility (NIF). Mitigating CBET assists in achieving ignition-relevant hot-spot pressures in deuterium-tritium cryogenic OMEGA implosions. In addition, reducing CBET permits lower, more hydrodynamically stable, in-flight aspect ratio ignition designs with smaller nonuniformity growth during the acceleration phase. Detuning the wavelengths of the crossing beams is one of several techniques under investigation at the University of Rochester to mitigate CBET. This talk will describe these techniques with an emphasis on wavelength detuning. Recent experiments designed and predicted using multidimensional hydrodynamic simulations including CBET on the NIF have exploited the wavelength arrangement of the NIF beam geometry to demonstrate CBET mitigation through wavelength detuning in polar-direct-drive (PDD) implosions. Shapes and trajectories inferred from time-resolved x-ray radiography of the imploding shell, scattered-light spectra, and hard x-ray spectra generated by suprathermal electrons all indicate a reduction in CBET. These results and their implications for direct-drive ignition will be presented and discussed. In addition, hydrodynamically scaled ignition-relevant designs for OMEGA implosions exploiting wavelength detuning will be presented. Changes required to the OMEGA laser to permit wavelength detuning will be discussed. Future plans for PDD on the NIF including more-uniform implosions with CBET mitigation will be explored. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

X-ray continuum as a measure of pressure and fuel–shell mix in compressed isobaric hydrogen implosion cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Epstein, R.; Goncharov, V. N.; Marshall, F. J.

Pressure, by definition, characterizes the conditions within an isobaric implosion core at peak compression [Gus'kov et al., Nucl. Fusion 16, 957 (1976); Betti et al., Phys. Plasmas 8, 5257 (2001)] and is a key parameter in quantifying its near-ignition performance [Lawson, Proc. Phys. Soc. London, B 70, 6 (1957); Betti et al., Phys. Plasmas 17, 058102 (2010); Goncharov et al., Phys. Plasmas 21, 056315 (2014); and Glenzer et al., Phys. Plasmas 19, 056318 (2012)]. At high spectral energy, where the x-ray emission from an imploded hydrogen core is optically thin, the emissivity profile can be inferred from the spatially resolvedmore » core emission. This emissivity, which can be modeled accurately under hot-core conditions, is dependent almost entirely on the pressure when measured within a restricted spectral range matched to the temperature range anticipated for the emitting volume. In this way, the hot core pressure at the time of peak emission can be inferred from the measured free-free emissivity profile. The pressure and temperature dependences of the x-ray emissivity and the neutron-production rate explain a simple scaling of the total filtered x-ray emission as a constant power of the total neutron yield for implosions of targets of similar design over a broad range of shell implosion isentropes. This scaling behavior has been seen in implosion simulations and is confirmed by measurements of high-isentrope implosions [Sangster et al., Phys. Plasmas 20, 056317 (2013)] on the OMEGA laser system [Boehly et al., Opt. Commun. 133, 495 (1997)]. Attributing the excess emission from less-stable, low-isentrope implosions, above the level expected from this neutron-yield scaling, to the higher emissivity of shell carbon mixed into the implosion's central hot spot, the hot-spot “fuel–shell” mix mass can be inferred.« less

Inertial Confinement Fusion Quarterly Report: April--June 1993. Volume 3, Number 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacGowan, B.J.; Kotowski, M.; Schleich, D.

1993-11-01

This issue of the ICF Quarterly contains six articles describing recent advances in Lawrence Livermore National Laboratory`s inertial confinement fusion (ICF) program. The current emphasis of the ICF program is in support of DOE`s National Ignition Facility (NIF) initiative for demonstrating ignition and gain with a 1-2 MJ glass laser. The articles describe recent Nova experiments and investigations tailored towards enhancing understanding of the key physics and technological issues for the NIF. Titles of the articles are: development of large-aperture KDP crystals; inner-shell photo-ionized X-ray lasers; X-ray radiographic measurements of radiation-driven shock and interface motion in solid density materials; themore » role of nodule defects in laser-induced damage of multilayer optical coatings; techniques for Mbar to near-Gbar equation-of-state measurements with the Nova laser; parametric instabilities and laser-beam smoothing.« less

Measuring spatial distributions of nuclear burn in ICF implosions at OMEGA and the NIF using proton emission imaging

NASA Astrophysics Data System (ADS)

Seguin, Fredrick; Rinderknecht, H. G.; Zylstra, A.; Sio, H.; Frenje, J.; Li, C. K.; Petrasso, R.; Rosenberg, M.; Marshall, F. J.; Sangster, T. C.; McKenty, P.; Craxton, S.; Rygg, J. R.; Le Pape, S.; Smalyuk, V.; Amendt, P. A.; Wilks, S. C.; MacKinnon, A.; Hoffman, N. M.

2015-11-01

Fusion reactions in ICF implosions of D3He-filled capsules produce 14.7-MeV D3He protons and 3-MeV DD protons. Spatial distributions of the D3He and DD reactions are studied with a penumbral imaging camera that utilizes a CR-39-based imaging detector to detect the protons. Up to three orthogonal cameras have been used simultaneously at OMEGA to study the 3-D structure of asymmetric implosions, and two orthogonal cameras have now been used to study an exploding-pusher implosion at the NIF. Recent data from OMEGA and from the NIF will be shown. This work was supported in part by NLUF, US DOE, and LLE.

The role of hot spot mix in the low-foot and high-foot implosions on the NIF

NASA Astrophysics Data System (ADS)

Ma, T.; Patel, P. K.; Izumi, N.; Springer, P. T.; Key, M. H.; Atherton, L. J.; Barrios, M. A.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Callahan, D. A.; Casey, D. T.; Celliers, P. M.; Cerjan, C. J.; Church, J. A.; Clark, D. S.; Dewald, E. L.; Dittrich, T. R.; Dixit, S. N.; Döppner, T.; Dylla-Spears, R.; Edgell, D. H.; Epstein, R.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Glenn, S.; Glenzer, S. H.; Grim, G.; Guler, N.; Haan, S. W.; Hammel, B. A.; Hatarik, R.; Herrmann, H. W.; Hicks, D.; Hinkel, D. E.; Berzak Hopkins, L. F.; Hsing, W. W.; Hurricane, O. A.; Jones, O. S.; Kauffman, R.; Khan, S. F.; Kilkenny, J. D.; Kline, J. L.; Kozioziemski, B.; Kritcher, A.; Kyrala, G. A.; Landen, O. L.; Lindl, J. D.; Le Pape, S.; MacGowan, B. J.; Mackinnon, A. J.; MacPhee, A. G.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Moses, E. I.; Nagel, S. R.; Nikroo, A.; Pak, A.; Parham, T.; Park, H.-S.; Ralph, J. E.; Regan, S. P.; Remington, B. A.; Robey, H. F.; Rosen, M. D.; Rygg, J. R.; Ross, J. S.; Salmonson, J. D.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Sio, H.; Spears, B. K.; Smalyuk, V.; Suter, L. J.; Tommasini, R.; Town, R. P. J.; Volegov, P. L.; Wan, A.; Weber, S. V.; Widmann, K.; Wilde, C. H.; Yeamans, C.; Edwards, M. J.

2017-05-01

Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the "low-foot" class of implosions appears to have been mix. Lower convergence "high-foot" implosions are found to be less susceptible to mix, allowing velocities of >380 km/s to be achieved.

Convergent ablation measurements of plastic ablators in gas-filled rugby hohlraums on OMEGA

NASA Astrophysics Data System (ADS)

Casner, A.; Jalinaud, T.; Masse, L.; Galmiche, D.

2015-10-01

Indirect-drive implosions experiments were conducted on the Omega Laser Facility to test the performance of uniformly doped plastic ablators for Inertial Confinement Fusion. The first convergent ablation measurements in gas-filled rugby hohlraums are reported. Ignition relevant limb velocities in the range from 150 to 300 μm .n s-1 have been reached by varying the laser drive energy and the initial capsule aspect ratio. The measured capsule trajectory and implosion velocity are in good agreement with 2D integrated simulations and a zero-dimensional modeling of the implosions. We demonstrate experimentally the scaling law for the maximum implosion velocity predicted by the improved rocket model [Y. Saillard, Nucl. Fusion 46, 1017 (2006)] in the high-ablation regime case.

Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruby, J. J.; Pak, A., E-mail: pak5@llnl.gov; Field, J. E.

2016-07-15

A technique for measuring residual motion during the stagnation phase of an indirectly driven inertial confinement experiment has been implemented. This method infers a velocity from spatially and temporally resolved images of the X-ray emission from two orthogonal lines of sight. This work investigates the accuracy of recovering spatially resolved velocities from the X-ray emission data. A detailed analytical and numerical modeling of the X-ray emission measurement shows that the accuracy of this method increases as the displacement that results from a residual velocity increase. For the typical experimental configuration, signal-to-noise ratios, and duration of X-ray emission, it is estimatedmore » that the fractional error in the inferred velocity rises above 50% as the velocity of emission falls below 24 μm/ns. By inputting measured parameters into this model, error estimates of the residual velocity as inferred from the X-ray emission measurements are now able to be generated for experimental data. Details of this analysis are presented for an implosion experiment conducted with an unintentional radiation flux asymmetry. The analysis shows a bright localized region of emission that moves through the larger emitting volume at a relatively higher velocity towards the location of the imposed flux deficit. This technique allows for the possibility of spatially resolving velocity flows within the so-called central hot spot of an implosion. This information would help to refine our interpretation of the thermal temperature inferred from the neutron time of flight detectors and the effect of localized hydrodynamic instabilities during the stagnation phase. Across several experiments, along a single line of sight, the average difference in magnitude and direction of the measured residual velocity as inferred from the X-ray and neutron time of flight detectors was found to be ∼13 μm/ns and ∼14°, respectively.« less

Spatially resolved X-ray emission measurements of the residual velocity during the stagnation phase of inertial confinement fusion implosion experiments

DOE PAGES

Ruby, J. J.; Pak, A.; Field, J. E.; ...

2016-07-01

A technique for measuring residual motion during the stagnation phase of an indirectly driven inertial confinement experiment has been implemented. Our method infers a velocity from spatially and temporally resolved images of the X-ray emission from two orthogonal lines of sight. This work investigates the accuracy of recovering spatially resolved velocities from the X-ray emission data. A detailed analytical and numerical modeling of the X-ray emission measurement shows that the accuracy of this method increases as the displacement that results from a residual velocity increase. For the typical experimental configuration, signal-to-noise ratios, and duration of X-ray emission, it is estimatedmore » that the fractional error in the inferred velocity rises above 50% as the velocity of emission falls below 24 μm/ns. Furthermore, by inputting measured parameters into this model, error estimates of the residual velocity as inferred from the X-ray emission measurements are now able to be generated for experimental data. Details of this analysis are presented for an implosion experiment conducted with an unintentional radiation flux asymmetry. The analysis shows a bright localized region of emission that moves through the larger emitting volume at a relatively higher velocity towards the location of the imposed flux deficit. Our technique allows for the possibility of spatially resolving velocity flows within the so-called central hot spot of an implosion. This information would help to refine our interpretation of the thermal temperature inferred from the neutron time of flight detectors and the effect of localized hydrodynamic instabilities during the stagnation phase. Across several experiments, along a single line of sight, the average difference in magnitude and direction of the measured residual velocity as inferred from the X-ray and neutron time of flight detectors was found to be ~13 μm/ns and ~14°, respectively.« less

Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

DOE PAGES

Johns, H. M.; Mancini, R. C.; Nagayama, T.; ...

2016-01-25

In warm target direct-drive inertial confinement fusion implosion experiments performed at the OMEGA laser facility, plastic micro-balloons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. Thesemore » 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400 ± 28 eV, electron number density (N e) = 8.5 × 10 24 ± 2.5 × 10 24 cm –3, and average areal density = 86 ± 7 mg/cm 2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2–9, dominated by l = 2. We extract a target breakup fraction of 7.1 ± 1.5% from our Fourier analysis. Furthermore, a new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5 ±1 μm.« less

High-resolution modeling of indirectly driven high-convergence layered inertial confinement fusion capsule implosions

DOE PAGES

Haines, Brian M.; Aldrich, C. H.; Campbell, J. M.; ...

2017-04-24

In this study, we present the results of high-resolution simulations of the implosion of high-convergence layered indirect-drive inertial confinement fusion capsules of the type fielded on the National Ignition Facility using the xRAGE radiation-hydrodynamics code. In order to evaluate the suitability of xRAGE to model such experiments, we benchmark simulation results against available experimental data, including shock-timing, shock-velocity, and shell trajectory data, as well as hydrodynamic instability growth rates. We discuss the code improvements that were necessary in order to achieve favorable comparisons with these data. Due to its use of adaptive mesh refinement and Eulerian hydrodynamics, xRAGE is particularlymore » well suited for high-resolution study of multi-scale engineering features such as the capsule support tent and fill tube, which are known to impact the performance of high-convergence capsule implosions. High-resolution two-dimensional (2D) simulations including accurate and well-resolved models for the capsule fill tube, support tent, drive asymmetry, and capsule surface roughness are presented. These asymmetry seeds are isolated in order to study their relative importance and the resolution of the simulations enables the observation of details that have not been previously reported. We analyze simulation results to determine how the different asymmetries affect hotspot reactivity, confinement, and confinement time and how these combine to degrade yield. Yield degradation associated with the tent occurs largely through decreased reactivity due to the escape of hot fuel mass from the hotspot. Drive asymmetries and the fill tube, however, degrade yield primarily via burn truncation, as associated instability growth accelerates the disassembly of the hotspot. Finally, modeling all of these asymmetries together in 2D leads to improved agreement with experiment but falls short of explaining the experimentally observed yield degradation, consistent with previous 2D simulations of such capsules.« less

Novae as Tevatrons: prospects for CTA and IceCube

NASA Astrophysics Data System (ADS)

Metzger, B. D.; Caprioli, D.; Vurm, I.; Beloborodov, A. M.; Bartos, I.; Vlasov, A.

2016-04-01

The discovery of novae as sources of ˜0.1-1 GeV gamma-rays highlights the key role of shocks and relativistic particle acceleration in these transient systems. Although there is evidence for a spectral cut-off above energies ˜1-100 GeV at particular epochs in some novae, the maximum particle energy achieved in these accelerators has remained an open question. The high densities of the nova ejecta (˜10 orders of magnitude larger than in supernova remnants) render the gas far upstream of the shock neutral and shielded from ionizing radiation. The amplification of the magnetic field needed for diffusive shock acceleration requires ionized gas, thus confining the acceleration process to a narrow photoionized layer immediately ahead of the shock. Based on the growth rate of the hybrid non-resonant cosmic ray current-driven instability (considering also ion-neutral damping), we quantify the maximum particle energy, Emax, across the range of shock velocities and upstream densities of interest. We find values of Emax ˜ 10 GeV-10 TeV, which are broadly consistent with the inferred spectral cut-offs, but which could also in principle lead to emission extending to ≳ 100 GeV accessible to atmosphere Cherenkov telescopes, such as the Cherenkov Telescope Array (CTA). Detecting TeV neutrinos with IceCube is more challenging, although the prospects are improved for a nearby event (≲ kpc) or if the shock power during the earliest, densest phases of the outburst is higher than implied by the GeV light curves, due to downscattering of the gamma-rays within the ejecta.

Experimental demonstration of the stabilizing effect of dielectric coatings on magnetically accelerated imploding metallic liners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awe, Thomas James; Peterson, Kyle J.; Yu, Edmund P.

Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70 μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=R in,0/R in(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. Lastly, the inner-wall radius R in(z,t) displayed unprecedented uniformity, varying from 95 to 130 μm over the 4.0 mm axial height captured by the radiograph.

Progress toward a unified kJ-machine CANDY

NASA Astrophysics Data System (ADS)

Kitagawa, Yoneyoshi; Mori, Yoshitaka; Komeda, Osamu; Hanayama, Ryohei; Ishii, Katsuhiro; Okihara, Shinichiro; Fujita, Kazuhisa; Nakayama, Suisei; Sekine, Takashi; Sato, Nakahiro; Kurita, Takashi; Kawashima, Toshiyuki; Watari, Takeshi; Kan, Hirofumi; Nakamura, Naoki; Kondo, Takuya; Fujine, Manabu; Azuma, Hirozumi; Motohiro, Tomoyoshi; Hioki, Tatsumi; Kakeno, Mitsutaka; Nishimura, Yasuhiko; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke; Arikawa, Yasunobu; Nagai, Takahiro; Abe, Yuki; Ozaki, Satoshi; Noda, Akira

2016-03-01

To construct a unified experimental machine CANDY using a kJ DPSSL driver in the fast-ignition scheme, the Laser for Fast Ignition Experiment (LFEX) at Osaka is used, showing that the laser-driven ions heat the preimploded core of a deuterated polystyrene (CD) shell target from 0.8 keV to 2 keV, resulting in 5 x 108 DD neutrons best ever obtained in the scheme. 4-J/10-Hz DPSSL laser HAMA is for the first time applied to the CD shell implosion- core heating experiments in the fast ignition scheme to yield neutrons and also to a continuous target injection, which yields neutrons of 3 x 105 n/4πsr n/shot.

Experimental demonstration of the stabilizing effect of dielectric coatings on magnetically accelerated imploding metallic liners

DOE PAGES

Awe, Thomas James; Peterson, Kyle J.; Yu, Edmund P.; ...

2016-02-10

Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70 μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=R in,0/R in(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. Lastly, the inner-wall radius R in(z,t) displayed unprecedented uniformity, varying from 95 to 130 μm over the 4.0 mm axial height captured by the radiograph.

Three-Dimensional Hydrodynamic Simulations of OMEGA Implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.

2016-10-01

The effects of large-scale (with Legendre modes less than 30) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming) and target offset, mount, and layers nonuniformities were investigated using three-dimensional (3-D) hydrodynamic simulations. Simulations indicate that the performance degradation in cryogenic implosions is caused mainly by the target offsets ( 10 to 20 μm), beampower imbalance (σrms 10 %), and initial target asymmetry ( 5% ρRvariation), which distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of the stagnated target. The ion temperature inferred from the width of simulated neutron spectra are influenced by bulk fuel motion in the distorted hot spot and can result in up to 2-keV apparent temperature increase. Similar temperature variations along different lines of sight are observed. Simulated x-ray images of implosion cores in the 4- to 8-keV energy range show good agreement with experiments. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires reducing large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing high-efficient mid-adiabat (α = 4) implosion designs that mitigate cross-beam energy transfer (CBET) and suppress short-wavelength Rayleigh-Taylor growth. These simulations use a new low-noise 3-D Eulerian hydrodynamic code ASTER. Existing 3-D hydrodynamic codes for direct-drive implosions currently miss CBET and noise-free ray-trace laser deposition algorithms. ASTER overcomes these limitations using a simplified 3-D laser-deposition model, which includes CBET and is capable of simulating the effects of beam-power imbalance, beam mispointing, mistiming, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Investigation of trailing mass in Z-pinch implosions and comparison to experiment

NASA Astrophysics Data System (ADS)

Yu, Edmund

2007-11-01

Wire-array Z pinches represent efficient, high-power x-ray sources with application to inertial confinement fusion, high energy density plasmas, and laboratory astrophysics. The first stage of a wire-array Z pinch is described by a mass ablation phase, during which stationary wires cook off material, which is then accelerated radially inwards by the JxB force. The mass injection rate varies axially and azimuthally, so that once the ablation phase concludes, the subsequent implosion is highly 3D in nature. In particular, a network of trailing mass and current is left behind the imploding plasma sheath, which can significantly affect pinch performance. In this work we focus on the implosion phase, electing to model the mass ablation via a mass injection scheme. Such a scheme has a number of injection parameters, but this freedom also allows us to gain understanding into the nature of the trailing mass network. For instance, a new result illustrates the role of azimuthal correlation. For an implosion which is 100% azimuthally correlated (corresponding to an azimuthally symmetric 2D r-z problem), current is forced to flow on the imploding plasma sheath, resulting in strong Rayleigh-Taylor (RT) growth. If, however, the implosion is not azimuthally symmetric, the additional azimuthal degree of freedom opens up new conducting paths of lower magnetic energy through the trailing mass network, effectively reducing RT growth. Consequently the 3D implosion experiences lower RT growth than the 2D r-z equivalent, and actually results in a more shell-like implosion. A second major goal of this work is to constrain the injection parameters by comparison to a well-diagnosed experimental data set, in which array mass was varied. In collaboration with R. Lemke, M. Desjarlais, M. Cuneo, C. Jennings, D. Sinars, E. Waisman

Theoretical and simulation research of hydrodynamic instabilities in inertial-confinement fusion implosions

NASA Astrophysics Data System (ADS)

Wang, LiFeng; Ye, WenHua; He, XianTu; Wu, JunFeng; Fan, ZhengFeng; Xue, Chuang; Guo, HongYu; Miao, WenYong; Yuan, YongTeng; Dong, JiaQin; Jia, Guo; Zhang, Jing; Li, YingJun; Liu, Jie; Wang, Min; Ding, YongKun; Zhang, WeiYan

2017-05-01

Inertial fusion energy (IFE) has been considered a promising, nearly inexhaustible source of sustainable carbon-free power for the world's energy future. It has long been recognized that the control of hydrodynamic instabilities is of critical importance for ignition and high-gain in the inertial-confinement fusion (ICF) hot-spot ignition scheme. In this mini-review, we summarize the progress of theoretical and simulation research of hydrodynamic instabilities in the ICF central hot-spot implosion in our group over the past decade. In order to obtain sufficient understanding of the growth of hydrodynamic instabilities in ICF, we first decompose the problem into different stages according to the implosion physics processes. The decomposed essential physics pro- cesses that are associated with ICF implosions, such as Rayleigh-Taylor instability (RTI), Richtmyer-Meshkov instability (RMI), Kelvin-Helmholtz instability (KHI), convergent geometry effects, as well as perturbation feed-through are reviewed. Analyti- cal models in planar, cylindrical, and spherical geometries have been established to study different physical aspects, including density-gradient, interface-coupling, geometry, and convergent effects. The influence of ablation in the presence of preheating on the RTI has been extensively studied by numerical simulations. The KHI considering the ablation effect has been discussed in detail for the first time. A series of single-mode ablative RTI experiments has been performed on the Shenguang-II laser facility. The theoretical and simulation research provides us the physical insights of linear and weakly nonlinear growths, and nonlinear evolutions of the hydrodynamic instabilities in ICF implosions, which has directly supported the research of ICF ignition target design. The ICF hot-spot ignition implosion design that uses several controlling features, based on our current understanding of hydrodynamic instabilities, to address shell implosion stability, has been briefly described, several of which are novel.

Higher Velocity High-Foot Implosions on the National Ignition Facility Laser

NASA Astrophysics Data System (ADS)

Callahan, Debra

2014-10-01

After the end of the National Ignition Campaign on the National Ignition Facility (NIF) laser, we began a campaign to test capsule performance using a modified laser pulse-shape that delivers higher power early in the pulse (``high foot''). This pulse-shape trades one-dimensional performance (peak compression) for increased hydrodynamic stability. The focus of the experiments this year have been to improve performance by increasing the implosion velocity using higher laser power/energy, depleted uranium hohlraums, and thinner capsules. While the mix of ablator material into the hotspot has been low for all of these implosions, the challenge has been to keep the implosion shape under control. As the peak laser power is increased, the plasma density in the hohlraum is increased - making it more and more challenging for the inner cone beams to reach the midplane of the hohlraum and resulting in an oblate implosion. Depleted uranium hohlraums have higher albedo than Au hohlraums, which leads to additional drive and improved implosion shape. Thinner ablators increase the velocity by reducing the amount of payload; thinner ablators also put less mass into the hohlraum which results in improved inner beam propagation. These techniques have allowed us to push the capsule to higher and higher velocity. In parallel with this effort, we are exploring other hohlraums such as the rugby shaped hohlraum to allow us to push these implosions further. This talk will summarize the progress of the high foot campaign in terms of both capsule and hohlraum performance. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The HEPCloud Facility: elastic computing for High Energy Physics - The NOvA Use Case

NASA Astrophysics Data System (ADS)

Fuess, S.; Garzoglio, G.; Holzman, B.; Kennedy, R.; Norman, A.; Timm, S.; Tiradani, A.

2017-10-01

The need for computing in the HEP community follows cycles of peaks and valleys mainly driven by conference dates, accelerator shutdown, holiday schedules, and other factors. Because of this, the classical method of provisioning these resources at providing facilities has drawbacks such as potential overprovisioning. As the appetite for computing increases, however, so does the need to maximize cost efficiency by developing a model for dynamically provisioning resources only when needed. To address this issue, the HEPCloud project was launched by the Fermilab Scientific Computing Division in June 2015. Its goal is to develop a facility that provides a common interface to a variety of resources, including local clusters, grids, high performance computers, and community and commercial Clouds. Initially targeted experiments include CMS and NOvA, as well as other Fermilab stakeholders. In its first phase, the project has demonstrated the use of the “elastic” provisioning model offered by commercial clouds, such as Amazon Web Services. In this model, resources are rented and provisioned automatically over the Internet upon request. In January 2016, the project demonstrated the ability to increase the total amount of global CMS resources by 58,000 cores from 150,000 cores - a 38 percent increase - in preparation for the Recontres de Moriond. In March 2016, the NOvA experiment has also demonstrated resource burst capabilities with an additional 7,300 cores, achieving a scale almost four times as large as the local allocated resources and utilizing the local AWS s3 storage to optimize data handling operations and costs. NOvA was using the same familiar services used for local computations, such as data handling and job submission, in preparation for the Neutrino 2016 conference. In both cases, the cost was contained by the use of the Amazon Spot Instance Market and the Decision Engine, a HEPCloud component that aims at minimizing cost and job interruption. This paper describes the Fermilab HEPCloud Facility and the challenges overcome for the CMS and NOvA communities.

Imaging of high-energy x-ray emission from cryogenic thermonuclear fuel implosions on the NIF.

PubMed

Ma, T; Izumi, N; Tommasini, R; Bradley, D K; Bell, P; Cerjan, C J; Dixit, S; Döppner, T; Jones, O; Kline, J L; Kyrala, G; Landen, O L; LePape, S; Mackinnon, A J; Park, H-S; Patel, P K; Prasad, R R; Ralph, J; Regan, S P; Smalyuk, V A; Springer, P T; Suter, L; Town, R P J; Weber, S V; Glenzer, S H

2012-10-01

Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide broadband time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered implosions. This diagnostic measures the temperature- and density-sensitive bremsstrahlung emission and provides estimates of hot spot mass, mix mass, and pressure.

Effects of electron-ion temperature equilibration on inertial confinement fusion implosions.

PubMed

Xu, Barry; Hu, S X

2011-07-01

The electron-ion temperature relaxation essentially affects both the laser absorption in coronal plasmas and the hot-spot formation in inertial confinement fusion (ICF). It has recently been reexamined for plasma conditions closely relevant to ICF implosions using either classical molecular-dynamics simulations or analytical methods. To explore the electron-ion temperature equilibration effects on ICF implosion performance, we have examined two Coulomb logarithm models by implementing them into our hydrocodes, and we have carried out hydrosimulations for ICF implosions. Compared to the Lee-More model that is currently used in our standard hydrocodes, the two models predict substantial differences in laser absorption, coronal temperatures, and neutron yields for ICF implosions at the OMEGA Laser Facility [Boehly et al. Opt. Commun. 133, 495 (1997)]. Such effects on the triple-picket direct-drive design at the National Ignition Facility (NIF) have also been explored. Based on the validity of the two models, we have proposed a combined model of the electron-ion temperature-relaxation rate for the overall ICF plasma conditions. The hydrosimulations using the combined model for OMEGA implosions have shown ∼6% more laser absorption, ∼6%-15% higher coronal temperatures, and ∼10% more neutron yield, when compared to the Lee-More model prediction. It is also noticed that the gain for the NIF direct-drive design can be varied by ∼10% among the different electron-ion temperature-relaxation models.

Explosion-Induced Implosions of Cylindrical Shell Structures

NASA Astrophysics Data System (ADS)

Ikeda, C. M.; Duncan, J. H.

2010-11-01

An experimental study of the explosion-induced implosion of cylindrical shell structures in a high-pressure water environment was performed. The shell structures are filled with air at atmospheric pressure and are placed in a large water-filled pressure vessel. The vessel is then pressurized to various levels P∞=αPc, where Pc is the natural implosion pressure of the model and α is a factor that ranges from 0.1 to 0.9. An explosive is then set off at various standoff distances, d, from the model center line, where d varies from R to 10R and R is the maximum radius of the explosion bubble. High-speed photography (27,000 fps) was used to observe the explosion and resulting shell structure implosion. High-frequency underwater blast sensors recorded dynamic pressure waves at 6 positions. The cylindrical models were made from aluminum (diameter D = 39.1 mm, wall thickness t = 0.89 mm, length L = 240 mm) and brass (D = 16.7 mm, t = 0.36 mm, L=152 mm) tubes. The pressure records are interpreted in light of the high-speed movies. It is found that the implosion is induced by two mechanisms: the shockwave generated by the explosion and the jet formed during the explosion-bubble collapse. Whether an implosion is caused by the shockwave or the jet depends on the maximum bubble diameter and the standoff distance.

Novel Characterization of Capsule X-Ray Drive at the National Ignition Facility [Using ViewFactor Experiments to Measure Hohlraum X-Radiation Drive from the Capsule Point-of-View in Ignition Experiments on the National Ignition Facility

DOE PAGES

MacLaren, S. A.; Schneider, M. B.; Widmann, K.; ...

2014-03-13

Here, indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%–25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the datamore » from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.« less

Double shell planar experiments on OMEGA

NASA Astrophysics Data System (ADS)

Dodd, E. S.; Merritt, E. C.; Palaniyappan, S.; Montgomery, D. S.; Daughton, W. S.; Schmidt, D. W.; Cardenas, T.; Wilson, D. C.; Loomis, E. N.; Batha, S. H.; Ping, Y.; Smalyuk, V. A.; Amendt, P. A.

2017-10-01

The double shell project is aimed at fielding neutron-producing capsules at the National Ignition Facility (NIF), in which an outer low-Z ablator collides with an inner high-Z shell to compress the fuel. However, understanding these targets experimentally can be challenging when compared with conventional single shell targets. Halfraum-driven planar targets at OMEGA are being used to study physics issues important to double shell implosions outside of a convergent geometry. Both VISAR and radiography through a tube have advantages over imaging through the hohlraum and double-shell capsule at NIF. A number physics issues are being studied with this platform that include 1-d and higher dimensional effects such as defect-driven hydrodynamic instabilities from engineering features. Additionally, the use of novel materials with controlled density gradients require study in easily diagnosed 1-d systems. This work ultimately feeds back into the NIF capsule platform through manufacturing tolerances set using data from OMEGA. Supported under the US DOE by the LANS, LLC under contract DE-AC52-06NA25396. LA-UR-17-25386.

Theoretical z -pinch scaling relations for thermonuclear-fusion experiments.

PubMed

Stygar, W A; Cuneo, M E; Vesey, R A; Ives, H C; Mazarakis, M G; Chandler, G A; Fehl, D L; Leeper, R J; Matzen, M K; McDaniel, D H; McGurn, J S; McKenney, J L; Muron, D J; Olson, C L; Porter, J L; Ramirez, J J; Seamen, J F; Speas, C S; Spielman, R B; Struve, K W; Torres, J A; Waisman, E M; Wagoner, T C; Gilliland, T L

2005-08-01

We have developed wire-array z -pinch scaling relations for plasma-physics and inertial-confinement-fusion (ICF) experiments. The relations can be applied to the design of z -pinch accelerators for high-fusion-yield (approximately 0.4 GJ/shot) and inertial-fusion-energy (approximately 3 GJ/shot) research. We find that (delta(a)/delta(RT)) proportional (m/l)1/4 (Rgamma)(-1/2), where delta(a) is the imploding-sheath thickness of a wire-ablation-dominated pinch, delta(RT) is the sheath thickness of a Rayleigh-Taylor-dominated pinch, m is the total wire-array mass, l is the axial length of the array, R is the initial array radius, and gamma is a dimensionless functional of the shape of the current pulse that drives the pinch implosion. When the product Rgamma is held constant the sheath thickness is, at sufficiently large values of m/l, determined primarily by wire ablation. For an ablation-dominated pinch, we estimate that the peak radiated x-ray power P(r) proportional (I/tau(i))(3/2)Rlphigamma, where I is the peak pinch current, tau(i) is the pinch implosion time, and phi is a dimensionless functional of the current-pulse shape. This scaling relation is consistent with experiment when 13 MA < or = I < or = 20 MA, 93 ns < or = tau(i) < or = 169 ns, 10 mm < or = R < or = 20 mm, 10 mm < or = l < or = 20 mm, and 2.0 mg/cm < or = m/l < or = 7.3 mg/cm. Assuming an ablation-dominated pinch and that Rlphigamma is held constant, we find that the x-ray-power efficiency eta(x) congruent to P(r)/P(a) of a coupled pinch-accelerator system is proportional to (tau(i)P(r)(7/9 ))(-1), where P(a) is the peak accelerator power. The pinch current and accelerator power required to achieve a given value of P(r) are proportional to tau(i), and the requisite accelerator energy E(a) is proportional to tau2(i). These results suggest that the performance of an ablation-dominated pinch, and the efficiency of a coupled pinch-accelerator system, can be improved substantially by decreasing the implosion time tau(i). For an accelerator coupled to a double-pinch-driven hohlraum that drives the implosion of an ICF fuel capsule, we find that the accelerator power and energy required to achieve high-yield fusion scale as tau(i)0.36 and tau(i)1.36, respectively. Thus the accelerator requirements decrease as the implosion time is decreased. However, the x-ray-power and thermonuclear-yield efficiencies of such a coupled system increase with tau(i). We also find that increasing the anode-cathode gap of the pinch from 2 to 4 mm increases the requisite values of P(a) and E(a) by as much as a factor of 2.

Implosion Dynamics and Mix in Double-Shell ICF Capsule Designs

NASA Astrophysics Data System (ADS)

Gunderson, Mark; Daughton, William; Simakov, Andrei; Wilson, Douglas; Watt, Robert; Delamater, Norman; Montgomery, David

2015-11-01

From an implosion dynamics perspective, double-shell ICF capsule designs have several advantages over the single-shell NIF ICF capsule point design. Double shell designs do not require precise shock sequencing, do not rely on hot spot ignition, have lower peak implosion speed requirements, and have lower convergence ratio requirements. However, there are still hurdles that must be overcome. The timing of the two main shocks in these designs is important in achieving sufficient compression of the DT fuel. Instability of the inner gold shell due to preheat from the hohlraum environment can disrupt the implosion of the inner pill. Mix, in addition to quenching burn in the DT fuel, also decreases the transfer of energy between the beryllium ablator and the inner gold shell during collision thus decreasing the implosion speed of the inner shell along with compression of the DT fuel. Herein, we will discuss practical implications of these effects on double-shell design we carry out in preparation for the NIF double-shell campaign. Work performed under the auspices of DOE by LANL under contract DE-AC52-06NA25396.

Profile modifications in laser-driven temperature fronts using flux-limiters and delocalization models

NASA Astrophysics Data System (ADS)

Colombant, Denis; Manheimer, Wallace; Busquet, Michel

2004-11-01

A simple steady-state model using flux-limiters by Day et al [1] showed that temperature profiles could formally be double-valued. Stability of temperature profiles in laser-driven temperature fronts using delocalization models was also discussed by Prasad and Kershaw [2]. We have observed steepening of the front and flattening of the maximum temperature in laser-driven implosions [3]. Following the simple model first proposed in [1], we solve for a two-boundary value steady-state heat flow problem for various non-local heat transport models. For the more complicated models [4,5], we obtain the steady-state solution as the asymptotic limit of the time-dependent solution. Solutions will be shown and compared for these various models. 1.M.Day, B.Merriman, F.Najmabadi and R.W.Conn, Contrib. Plasma Phys. 36, 419 (1996) 2.M.K.Prasad and D.S.Kershaw, Phys. Fluids B3, 3087 (1991) 3.D.Colombant, W.Manheimer and M.Busquet, Bull. Amer. Phys. Soc. 48, 326 (2003) 4.E.M.Epperlein and R.W.Short, Phys. Fluids B3, 3092 (1991) 5.W.Manheimer and D.Colombant, Phys. Plasmas 11, 260 (2004)

Advances in compact proton spectrometers for inertial-confinement fusion and plasma nuclear science.

PubMed

Seguin, F H; Sinenian, N; Rosenberg, M; Zylstra, A; Manuel, M J-E; Sio, H; Waugh, C; Rinderknecht, H G; Johnson, M Gatu; Frenje, J; Li, C K; Petrasso, R; Sangster, T C; Roberts, S

2012-10-01

Compact wedge-range-filter proton spectrometers cover proton energies ∼3-20 MeV. They have been used at the OMEGA laser facility for more than a decade for measuring spectra of primary D(3)He protons in D(3)He implosions, secondary D(3)He protons in DD implosions, and ablator protons in DT implosions; they are now being used also at the National Ignition Facility. The spectra are used to determine proton yields, shell areal density at shock-bang time and compression-bang time, fuel areal density, and implosion symmetry. There have been changes in fabrication and in analysis algorithms, resulting in a wider energy range, better accuracy and precision, and better robustness for survivability with indirect-drive inertial-confinement-fusion experiments.

The role of hot spot mix in the low-foot and high-foot implosions on the NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, T.; Patel, P. K.; Izumi, N.

Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the “low-foot” class of implosions appears to have been mix. As a result, lower convergence “high-foot” implosions are found to be lessmore » susceptible to mix, allowing velocities of >380 km/s to be achieved.« less

The role of hot spot mix in the low-foot and high-foot implosions on the NIF

DOE PAGES

Ma, T.; Patel, P. K.; Izumi, N.; ...

2017-05-18

Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the “low-foot” class of implosions appears to have been mix. As a result, lower convergence “high-foot” implosions are found to be lessmore » susceptible to mix, allowing velocities of >380 km/s to be achieved.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurricane, O. A.; Clark, D. S.

The work is summarized from several perspectives: 1D simulation perspective: Post-shot models agree with yield data to within a factor of ~2 at low implosion velocities, but the models diverge from the data as the velocity and convergence ratio increase. 2D simulation perspective: Integrated hohlraum-capsule post-shot models agree with primary data for most implosions, but overpredict yield and DSR for a few of the highest velocity implosions. High-resolution 3D post-shot capsule-only modeling captures much of the delivered performance of the one shot currently simulated.

Inertial confinement fusion method producing line source radiation fluence

DOEpatents

Rose, Ronald P.

1984-01-01

An inertial confinement fusion method in which target pellets are imploded in sequence by laser light beams or other energy beams at an implosion site which is variable between pellet implosions along a line. The effect of the variability in position of the implosion site along a line is to distribute the radiation fluence in surrounding reactor components as a line source of radiation would do, thereby permitting the utilization of cylindrical geometry in the design of the reactor and internal components.

Non-LTE modeling for the National Ignition Facility (and beyond)

NASA Astrophysics Data System (ADS)

Scott, H. A.; Hammel, B. A.; Hansen, S. B.

2012-05-01

Considerable progress has been made in the last year in the study of laser-driven inertial confinement fusion at the National Ignition Facility (NIF). Experiments have demonstrated symmetric capsule implosions with plasma conditions approaching those required for ignition. Improvements in computational models - in large part due to advances in non-LTE modeling - have resulted in simulations that match experimental results quite well for the X-ray drive, implosion symmetry and total wall emission [1]. Non-LTE modeling is a key part of the NIF simulation effort, affecting several aspects of experimental design and diagnostics. The X-rays that drive the capsule arise from high-Z material ablated off the hohlraum wall. Current capsule designs avoid excessive preheat from high-energy X-rays by shielding the fuel with a mid-Z dopant, which affects the capsule dynamics. The dopant also mixes into the hot spot through hydrodynamic instabilities, providing diagnostic possibilities but potentially impacting the energy balance of the capsule [2]. Looking beyond the NIF, a proposed design for a fusion reactor chamber depends on lowdensity high-Z gas absorbing X-rays and particles to protect the first wall [3]. These situations encompass a large range of temperatures, densities and spatial scales. They each emphasize different aspects of atomic physics and present a variety of challenges for non-LTE modeling. We discuss the relevant issues and summarize the current state of the modeling effort for these applications.

A novel particle time of flight diagnostic for measurements of shock- and compression-bang times in D3He and DT implosions at the NIF.

PubMed

Rinderknecht, H G; Johnson, M Gatu; Zylstra, A B; Sinenian, N; Rosenberg, M J; Frenje, J A; Waugh, C J; Li, C K; Sèguin, F H; Petrasso, R D; Rygg, J R; Kimbrough, J R; MacPhee, A; Collins, G W; Hicks, D; Mackinnon, A; Bell, P; Bionta, R; Clancy, T; Zacharias, R; Döppner, T; Park, H S; LePape, S; Landen, O; Meezan, N; Moses, E I; Glebov, V U; Stoeckl, C; Sangster, T C; Olson, R; Kline, J; Kilkenny, J

2012-10-01

The particle-time-of-flight (pTOF) diagnostic, fielded alongside a wedge range-filter (WRF) proton spectrometer, will provide an absolute timing for the shock-burn weighted ρR measurements that will validate the modeling of implosion dynamics at the National Ignition Facility (NIF). In the first phase of the project, pTOF has recorded accurate bang times in cryogenic DT, DT exploding pusher, and D(3)He implosions using DD or DT neutrons with an accuracy better than ±70 ps. In the second phase of the project, a deflecting magnet will be incorporated into the pTOF design for simultaneous measurements of shock- and compression-bang times in D(3)He-filled surrogate implosions using D(3)He protons and DD-neutrons, respectively.

The pressure field of imploding lightbulbs

NASA Astrophysics Data System (ADS)

Czechanowski, M.; Ikeda, C.; Duncan, J. H.

2015-03-01

The implosion of A19 incandescent lightbulbs in a high-pressure water environment is studied in a 1.77-m-diameter steel tank. Underwater blast sensors are used to measure the dynamic pressure field near the lightbulbs and the implosions are photographed with a high-speed movie camera at a frame rate of 24,000 pps. The movie camera and the pressure signal recording system are synchronized to enable correlation of features in the movie frames with those in the pressure records. It is found that the gross dimensions and weight of the bulbs are very similar from one bulb to another, but the ambient water pressure at which a given bulb implodes (, called the implosion pressure) varies from 6.29 to 11.98 atmospheres, probably due to inconsistencies in the glass wall thickness and perhaps other detailed characteristics of the bulbs. The dynamic pressures (the local pressure minus , as measured by the sensors) first drop during the implosion and then reach a strong positive peak at about the time that the bulb reaches minimum volume. The peak dynamic pressure varies from 3.61 to 28.66 atmospheres. In order to explore the physics of the implosion process, the dynamic pressure signals are compared to calculations of the pressure field generated by the collapse of a spherical bubble in a weakly compressible liquid. The wide range of implosion pressures is used in combination with the calculations to explore the effect of the relative liquid compressibility and the bulb itself on the dynamic pressure field.

Unambiguous Evidence of Coronal Implosions during Solar Eruptions and Flares

NASA Astrophysics Data System (ADS)

Wang, Juntao; Simões, P. J. A.; Fletcher, L.

2018-05-01

In the implosion conjecture, coronal loops contract as the result of magnetic energy release in solar eruptions and flares. However, after almost two decades, observations of this phenomenon are still rare and most previous reports are plagued by projection effects so that loop contraction could be either true implosion or just a change in loop inclination. In this paper, to demonstrate the reality of loop contractions in the global coronal dynamics, we present four events with the continuously contracting loops in an almost edge-on geometry from the perspective of SDO/AIA, which are free from the ambiguity caused by the projection effects, also supplemented by contemporary observations from STEREO for examination. In the wider context of observations, simulations and theories, we argue that the implosion conjecture is valid in interpreting these events. Furthermore, distinct properties of the events allow us to identify two physical categories of implosion. One type demonstrates a rapid contraction at the beginning of the flare impulsive phase, as magnetic free energy is removed rapidly by a filament eruption. The other type, which has no visible eruption, shows a continuous loop shrinkage during the entire flare impulsive phase, which we suggest shows the ongoing conversion of magnetic free energy in a coronal volume. Corresponding scenarios are described that can provide reasonable explanations for the observations. We also point out that implosions may be suppressed in cases when a heavily mass-loaded filament is involved, possibly serving as an alternative account for their observational rarity.

Polar-Drive--Implosion Physics on OMEGA and the NIF

NASA Astrophysics Data System (ADS)

Radha, P. B.

2012-10-01

Polar drive (PD) permits the execution of direct-drive--ignition experiments on facilities that are configured for x-ray drive such as the National Ignition Facility (NIF) and Laser M'egajoule. Experiments on the OMEGA laser are used to develop and validate models of PD implosions. Results from OMEGA PD shock-timing and warm implosions are presented. Experiments are simulated with the 2-D hydrodynamic code DRACO including full 3-D ray trace to model oblique beams. Excellent agreement is obtained in shock velocity and catch-up in PD geometry in warm, plastic shells. Predicted areal densities are measured in PD implosion experiments. Good agreement between simulation and experiments is obtained in the overall shape of the compressing shell when observed through x-ray backlighting. Simulated images of the hot core, including the effect of magnetic fields, are compared with experiments. Comparisons of simulated and observed scattered light and bang time in PD geometry are presented. Several techniques to increase implosion velocity are presented including beam profile variations and different ablator materials. Results from shimmed-target PD experiments will also be presented. Designs for future PD OMEGA experiments at ignition-relevant intensities will be presented. The implication of these results for NIF-scale plasmas is discussed. Experiments for the NIF in its current configuration, with indirect-drive phase plates, are proposed to study implosion energetics and shell asymmetries. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

Neutron spectrometry - An essential tool for diagnosing implosions at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mackinnon, A J; Johnson, M G; Frenje, J A

DT neutron yield (Y{sub n}), ion temperature (T{sub i}) and down-scatter ratio (dsr) determined from measured neutron spectra are essential metrics for diagnosing the performance of Inertial Confinement Fusion (ICF) implosions at the National Ignition Facility (NIF). A suite of neutron-Time-Of-Flight (nTOF) spectrometers and a Magnetic Recoil Spectrometer (MRS) have been implemented in different locations around the NIF target chamber, providing good implosion coverage and the redundancy required for reliable measurements of Yn, Ti and dsr. From the measured dsr value, an areal density ({rho}R) is determined from the relationship {rho}R{sub tot} (g/cm{sup 2}) = (20.4 {+-} 0.6) x dsr{submore » 10-12 MeV}. The proportionality constant is determined considering implosion geometry, neutron attenuation and energy range used for the dsr measurement. To ensure high accuracy in the measurements, a series of commissioning experiments using exploding pushers have been used for in situ calibration. The spectrometers are now performing to the required accuracy, as indicated by the good agreement between the different measurements over several commissioning shots. In addition, recent data obtained with the MRS and nTOFs indicate that the implosion performance of cryogenically layered DT implosions, characterized by the experimental Ignition Threshold Factor (ITFx) which is a function of dsr (or fuel {rho}R) and Y{sub n}, has improved almost two orders of magnitude since the first shot in September, 2010.« less

Neutron spectrometry-An essential tool for diagnosing implosions at the National Ignition Facility (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, M. Gatu; Frenje, J. A.; Casey, D. T.

2012-10-15

DT neutron yield (Y{sub n}), ion temperature (T{sub i}), and down-scatter ratio (dsr) determined from measured neutron spectra are essential metrics for diagnosing the performance of inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF). A suite of neutron-time-of-flight (nTOF) spectrometers and a magnetic recoil spectrometer (MRS) have been implemented in different locations around the NIF target chamber, providing good implosion coverage and the complementarity required for reliable measurements of Y{sub n}, T{sub i}, and dsr. From the measured dsr value, an areal density ({rho}R) is determined through the relationship {rho}R{sub tot} (g/cm{sup 2}) = (20.4 {+-} 0.6)more » Multiplication-Sign dsr{sub 10-12MeV}. The proportionality constant is determined considering implosion geometry, neutron attenuation, and energy range used for the dsr measurement. To ensure high accuracy in the measurements, a series of commissioning experiments using exploding pushers have been used for in situ calibration of the as-built spectrometers, which are now performing to the required accuracy. Recent data obtained with the MRS and nTOFs indicate that the implosion performance of cryogenically layered DT implosions, characterized by the experimental ignition threshold factor (ITFx), which is a function of dsr (or fuel {rho}R) and Y{sub n}, has improved almost two orders of magnitude since the first shot in September, 2010.« less

Fusion in a staged Z-pinch

NASA Astrophysics Data System (ADS)

Wessel, F. J.; Rahman, H. U.; Ney, P.; Valenzuela, J.; Beg, F.; McKee, E.; Darling, T.

2016-03-01

This paper is dedicated to Norman Rostoker, our (FJW and HUR) mentor and long-term collaborator, who will always be remembered for the incredible inspiration that he has provided us. Norman's illustrious career dealt with a broad range of fundamental-physics problems and we were fortunate to have worked with him on many important topics: intense-charged-particle beams, field-reversed configurations, and Z-pinches. Rostoker 's group at the University of CA, Irvine was well known for having implemented many refinements to the Z-pinch, that make it more stable, scalable, and efficient, including the development of: the gas-puff Z-pinch [1], which provides for the use of an expanded range of pinch-load materials; the gas-mixture Z-pinch [2], which enhances the pinch stability and increases its radiation efficiency; e-beam pre-ionization [3], which enhances the uniformity of the initial-breakdown process in a gas pinch; magnetic-flux-compression [4, 5], which allows for the amplification of an axial-magnetic field Bz; the Z-θ pinch [6], which predicts fusion in a pinch-on-fiber configuration; the Staged Z-pinch (SZP) [7], which allows for the amplification of the pinch self-magnetic field, Bθ , in addition to a Bz, and leads to a stable implosion and high-gain fusion [8, 9, 10]. This paper describes the physical basis for a magneto-inertial compression in a liner-on-target SZP [11]. Initially a high-atomic-number liner implodes under the action of the J →×B → , Lorentz Force. As the implosion becomes super Alfvénic, magnetosonic waves form, transporting current and magnetic field through the liner toward the interface of the low-atomic-number target. The target implosion remains subsonic with its surface bounded by a stable-shock front. Shock waves that pass into the target provide a source of target plasma pre-heat. At peak compression the assembly is compressed by liner inertia, with flux compression producing an intense-magnetic field near the target. Instability develops at the interface, as the plasma decelerates, which promotes the formation of target-hot spots. Early experiments provide evidence for the magneto-inertial implosion [8, 9, 10]. Studies underway are designed to verify these predictions on the National Terawatt Facility, Zebra Generator, located at the University of Nevada, Reno. Simulations for an unmagnetized, silver-plasma liner imploding onto a deuterium-tritium plasma target, driven by a 200 TW generator, predict fusion beyond break-even, with a 200 MJ yield in an ignited plasma, with an engineering gain factor of, G = Efusion/Estored˜20.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Guoyong; Budny, Robert; Gorelenkov, Nikolai

We report here the work done for the FY14 OFES Theory Performance Target as given below: "Understanding alpha particle confinement in ITER, the world's first burning plasma experiment, is a key priority for the fusion program. In FY 2014, determine linear instability trends and thresholds of energetic particle-driven shear Alfven eigenmodes in ITER for a range of parameters and profiles using a set of complementary simulation models (gyrokinetic, hybrid, and gyrofluid). Carry out initial nonlinear simulations to assess the effects of the unstable modes on energetic particle transport". In the past year (FY14), a systematic study of the alpha-driven Alfvenmore » modes in ITER has been carried out jointly by researchers from six institutions involving seven codes including the transport simulation code TRANSP (R. Budny and F. Poli, PPPL), three gyrokinetic codes: GEM (Y. Chen, Univ. of Colorado), GTC (J. McClenaghan, Z. Lin, UCI), and GYRO (E. Bass, R. Waltz, UCSD/GA), the hybrid code M3D-K (G.Y. Fu, PPPL), the gyro-fluid code TAEFL (D. Spong, ORNL), and the linear kinetic stability code NOVA-K (N. Gorelenkov, PPPL). A range of ITER parameters and profiles are specified by TRANSP simulation of a hybrid scenario case and a steady-state scenario case. Based on the specified ITER equilibria linear stability calculations are done to determine the stability boundary of alpha-driven high-n TAEs using the five initial value codes (GEM, GTC, GYRO, M3D-K, and TAEFL) and the kinetic stability code (NOVA-K). Both the effects of alpha particles and beam ions have been considered. Finally, the effects of the unstable modes on energetic particle transport have been explored using GEM and M3D-K.« less

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE PAGES

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; ...

2017-03-30

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.

By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1 × 10{sup 15} neutrons, the total yield ∼ v{sup 9.4}. This increase is considerably faster than the expected dependence for implosions without alpha heating (∼v{sup 5.9}) and is additional evidence that these experiments have significant alpha heating.« less

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

Ultra-processed foods in human health: a critical appraisal.

PubMed

Gibney, Michael J; Forde, Ciarán G; Mullally, Deirdre; Gibney, Eileen R

2017-09-01

The NOVA classification of foods proposes 4 categories: unprocessed or minimally processed foods, processed culinary ingredients, processed foods, and ultra-processed foods and drinks (UPFDs). It is argued that the latter relies heavily on modifications to foods, resulting in enhanced amounts of salt, added sugar, and fat as well as the use of additives in an attempt to make this food category highly palatable. It further argues that controlling food processing, rather than examining nutrients, should be foremost in shaping nutrition policy. This commentary challenges many of the basic arguments of using the NOVA food classification system to examine the link between food and health. We believe that there is no evidence to uphold the view that UPFDs give rise to hyperpalatable foods associated with a quasi-addictive effect and that the prevailing European Union and US data fail to uphold the assertion that UPFDs, which dominate energy intake, give rise to dietary patterns that are low in micronutrients. With regard to the use of the NOVA food classification in the development of food-based dietary guidelines, we show that the very broad definition of UPFDs makes this impossible. Finally, the available evidence does not support the view that the globalization of food is the driver of increased intakes of UPFDs in low- to middle-income countries but rather that this is driven by small indigenous companies. On balance, therefore, there seems to be little advantage from the use of the NOVA classification compared with the current epidemiologic approach, which relies on the linkage of nutrient intakes to chronic disease with subsequent identification of foods that merit consideration in public health nutrition strategies. © 2017 American Society for Nutrition.

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF

DOE PAGES

Ma, T.; Chen, H.; Patel, P. K.; ...

2016-08-18

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. We describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.Published by AIP Publishing

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF.

PubMed

Ma, T; Chen, H; Patel, P K; Schneider, M B; Barrios, M A; Casey, D T; Chung, H-K; Hammel, B A; Berzak Hopkins, L F; Jarrott, L C; Khan, S F; Lahmann, B; Nora, R; Rosenberg, M J; Pak, A; Regan, S P; Scott, H A; Sio, H; Spears, B K; Weber, C R

2016-11-01

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF

NASA Astrophysics Data System (ADS)

Ma, T.; Chen, H.; Patel, P. K.; Schneider, M. B.; Barrios, M. A.; Casey, D. T.; Chung, H.-K.; Hammel, B. A.; Berzak Hopkins, L. F.; Jarrott, L. C.; Khan, S. F.; Lahmann, B.; Nora, R.; Rosenberg, M. J.; Pak, A.; Regan, S. P.; Scott, H. A.; Sio, H.; Spears, B. K.; Weber, C. R.

2016-11-01

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

Status On Multi-microsecond Prepulse Technique On Sphinx Machine Going From Nested To Single Wire Array For 800 ns Implosion Time Z-pinch

NASA Astrophysics Data System (ADS)

Maury, P.; Calamy, H.; Grunenwald, J.; Lassalle, F.; Zucchini, F.; Loyen, A.; Georges, A.; Morell, A.; Bedoch, J. P.

2009-01-01

The Sphinx machine[1] is a 6 MA, 1 μS driver based on the LTD technology, used for Z-pinch experiments. Important improvements of Sphinx radiation output were recently obtained using a multi-microsecond current prepulse[2]. Total power per unit of length is multiplied by a factor of 6 and FWHM divided by a factor of 2.5. Early breakdown of the wires during the prepulse phase dramatically changes the ablation phase leading to an improvement of axial homogeneity of both the implosion and the final radiating column. As a consequence, the cathode bubble observed on classical shots is definitively removed. The implosion is then centered and zippering effect is reduced, leading to simultaneous x-ray emission of the whole length. A great reproducibility is obtained. Nested arrays were used before to mitigate the Rayleigh-Taylor instabilities during the implosion phase. Further experiments with pre-pulse technique are described here were inner array was removed. The goal of these experiments was to see if long prepulse could give stable enough implosion with single array and at the same time increase the η parameter by reducing the mass of the load. Experimental results of single wire array loads of typical dimension 5 cm in height with implosion time between 700 and 900 ns and diameter varying between 80 and 140 mm are given. Parameters of the loads were varying in term of radius and number of wires. Comparisons with nested wire array loads are done and trends are proposed. Characteristics of both the implosion and the final radiating column are shown. 2D MHD numerical simulations of single wire array become easier as there is no interaction between outer and inner array anymore. A systematic study was done using injection mass model to benchmark simulation with experiments.

Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Weilacher, F.; Radha, P. B.; Forrest, C.

2018-04-01

Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium-tritium (D-T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. It is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D-D and D-T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D-D reaction, whereas they insignificantly influence the inferred D-T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. This code will continue to be used for post-processing detailed hydrodynamic simulations and interpreting observed neutron spectra in ICF implosions.

X-ray continuum as a measure of pressure and fuel–shell mix in compressed isobaric hydrogen implosion cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Epstein, R.; Goncharov, V. N.; Marshall, F. J.

Pressure, by definition, characterizes the conditions within an isobaric implosion core at peak compression [Gus’kov et al., Nucl. Fusion 16, 957 (1976); Betti et al., Phys. Plasmas 8, 5257 (2001)] and is a key parameter in quantifying its near-ignition performance [Lawson, Proc. Phys. Soc. London, B 70, 6 (1957); Betti et al., Phys. Plasmas 17, 058102 (2010); Goncharov et al., Phys. Plasmas 21, 056315 (2014); and Glenzer et al., Phys. Plasmas 19, 056318 (2012)]. At high spectral energy, where the x-ray emission from an imploded hydrogen core is optically thin, the emissivity profile can be inferred from the spatially resolvedmore » core emission. This emissivity, which can be modeled accurately under hot-core conditions, is dependent almost entirely on the pressure when measured within a restricted spectral range matched to the temperature range anticipated for the emitting volume. In this way, the hot core pressure at the time of peak emission can be inferred from the measured free-free emissivity profile. The pressure and temperature dependences of the x-ray emissivity and the neutron-production rate explain a simple scaling of the total filtered x-ray emission as a constant power of the total neutron yield for implosions of targets of similar design over a broad range of shell implosion isentropes. This scaling behavior has been seen in implosion simulations and is confirmed by measurements of high-isentrope implosions [Sangster et al., Phys. Plasmas 20, 056317 (2013)] on the OMEGA laser system [Boehly et al., Opt. Commun. 133, 495 (1997)]. Attributing the excess emission from less-stable, low-isentrope implosions, above the level expected from this neutron-yield scaling, to the higher emissivity of shell carbon mixed into the implosion’s central hot spot, the hot-spot “fuel–shell” mix mass can be inferred.« less

Hot spot temperature measurements in DT layered implosions

NASA Astrophysics Data System (ADS)

Patel, Pravesh; Ma, T.; Macphee, A.; Callahan, D.; Chen, H.; Cerjan, C.; Clark, D.; Edgell, D.; Hurricane, O.; Izumi, N.; Khan, S.; Jarrott, L.; Kritcher, A.; Springer, P.

2015-11-01

The temperature of the burning DT hot spot in an ICF implosion is a crucial parameter in understanding the thermodynamic conditions of the fuel at stagnation and and the performance of the implosion in terms of alpha-particle self-heating and energy balance. The continuum radiation spectrum emitted from the hot spot provides an accurate measure of the emissivity-weighted electron temperature. Absolute measurements of the emitted radiation are made with several independent instruments including spatially-resolved broadband imagers, and space- and time-integrated monochromatic detectors. We present estimates of the electron temperature in DT layered implosions derived from the radiation spectrum most consistent with the available measurements. The emissivity-weighted electron temperatures are compared to the neutron-averaged apparent ion temperatures inferred from neutron time-of-flight detectors. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Computational modeling of Krypton gas puffs with tailored mass density profiles on Z

DOE PAGES

Jennings, Christopher A.; Ampleford, David J.; Lamppa, Derek C.; ...

2015-05-18

Large diameter multi-shell gas puffs rapidly imploded by high current (~20 MA, ~100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity Krypton K-shell emission at ~13 keV. Efficiently radiating at these high photon energies is a significant challenge which requires the careful design and optimization of the gas distribution. To facilitate this, we hydrodynamically model the gas flow out of the nozzle and then model its implosion using a 3-dimensional resistive, radiative MHD code (GORGON). This approach enables us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiativemore » output from this combined system. Furthermore, guided by our implosion calculations, we have designed gas profiles that help mitigate disruption from Magneto-Rayleigh–Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission.« less

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

NASA Astrophysics Data System (ADS)

Regan, S. P.; Goncharov, V. N.; Igumenshchev, I. V.; Sangster, T. C.; Betti, R.; Bose, A.; Boehly, T. R.; Bonino, M. J.; Campbell, E. M.; Cao, D.; Collins, T. J. B.; Craxton, R. S.; Davis, A. K.; Delettrez, J. A.; Edgell, D. H.; Epstein, R.; Forrest, C. J.; Frenje, J. A.; Froula, D. H.; Gatu Johnson, M.; Glebov, V. Yu.; Harding, D. R.; Hohenberger, M.; Hu, S. X.; Jacobs-Perkins, D.; Janezic, R.; Karasik, M.; Keck, R. L.; Kelly, J. H.; Kessler, T. J.; Knauer, J. P.; Kosc, T. Z.; Loucks, S. J.; Marozas, J. A.; Marshall, F. J.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Michel, D. T.; Myatt, J. F.; Obenschain, S. P.; Petrasso, R. D.; Radha, P. B.; Rice, B.; Rosenberg, M. J.; Schmitt, A. J.; Schmitt, M. J.; Seka, W.; Shmayda, W. T.; Shoup, M. J.; Shvydky, A.; Skupsky, S.; Solodov, A. A.; Stoeckl, C.; Theobald, W.; Ulreich, J.; Wittman, M. D.; Woo, K. M.; Yaakobi, B.; Zuegel, J. D.

2016-07-01

A record fuel hot-spot pressure Phs=56 ±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ˜60 % of the value required for ignition [A. Bose et al., Phys. Rev. E 93, LM15119ER (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.

Demonstration of fuel hot-spot pressure in excess of 50 Gbar for direct-drive, layered deuterium-tritium implosions on OMEGA

DOE PAGES

Regan, S. P.; Goncharov, V. N.; Igumenshchev, I. V.; ...

2016-07-07

A record fuel hot-spot pressure P hs = 56±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium–tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility (NIF), these implosions achieved a Lawson parameter ~60% of the value required for ignition [A. Bose et al., Phys. Rev. E (in press)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure ismore » ~40% lower. Furthermore, three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.« less

Demonstration of fuel hot-spot pressure in excess of 50 Gbar for direct-drive, layered deuterium-tritium implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regan, S. P.; Goncharov, V. N.; Igumenshchev, I. V.

A record fuel hot-spot pressure P hs = 56±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium–tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility (NIF), these implosions achieved a Lawson parameter ~60% of the value required for ignition [A. Bose et al., Phys. Rev. E (in press)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure ismore » ~40% lower. Furthermore, three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.« less

Design of a Neutron Temporal Diagnostic for measuring DD or DT burn histories at the NIF

NASA Astrophysics Data System (ADS)

Lahmann, B.; Frenje, J. A.; Sio, H.; Petrasso, R. D.; Bradley, D. K.; Le Pape, S.; MacKinnon, A. J.; Isumi, N.; Macphee, A.; Zayas, C.; Spears, B. K.; Hermann, H.; Hilsabeck, T. J.; Kilkenny, J. D.

2015-11-01

The DD or DT burn history in Inertial Confinement Fusion (ICF) implosions provides essential information about implosion performance and helps to constrain numerical modeling. The capability of measuring this burn history is thus important for the NIF in its pursuit of ignition. Currently, the Gamma Reaction History (GRH) diagnostic is the only system capable of measuring the burn history for DT implosions with yields greater than ~ 1e14. To complement GRH, a new NIF Neutron Temporal Diagnostic (NTD) is being designed for measuring the DD or DT burn history with yields greater than ~ 1e10. A traditional scintillator-based design and a pulse-dilation-based design are being considered. Using MCNPX simulations, both designs have been optimized, validated and contrasted for various types of implosions at the NIF. This work was supported in part by the U.S. DOE, LLNL and LLE.

Designing cylindrical implosion experiments on NIF to study deceleration phase of Rayleigh-Taylor

NASA Astrophysics Data System (ADS)

Vazirani, N.; Kline, J. L.; Loomis, E.; Sauppe, J. P.; Palaniyappan, S.; Flippo, K.; Srinivasan, B.; Malka, E.; Bose, A.; Shvarts, D.

2017-10-01

The Rayleigh-Taylor (RT) hydrodynamic instability occurs when a lower density fluid pushes on a higher density fluid. This occurs in inertial confinement fusion (ICF) implosions at each of the capsule interfaces during the initial acceleration and the deceleration as it stagnates. The RT instabilities mix capsule material into the fusion fuel degrading the Deuterium-Tritium reactivity and ultimately play a key role in limiting target performance. While significant effort has focused on understanding RT at the outer capsule surface, little work has gone into understanding the inner surface RT instability growth during the deceleration phase. Direct measurements of the RT instability are difficult to make at high convergence in a spherical implosion. Here we present the design of a cylindrical implosion system for the National Ignition Facility for studying deceleration phase RT. We will discuss the experimental design, the estimated instability growth, and our outstanding concerns.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

DOE PAGES

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; ...

2015-11-19

In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, Neal G.; Vu, M.; Kong, C.

Capsule drive in National Ignition Facility (NIF) indirect drive implosions is generated by x-ray illumination from cylindrical hohlraums. The cylindrical hohlraum geometry is axially symmetric but not spherically symmetric causing capsule-fuel drive asymmetries. We hypothesize that fabricating capsules asymmetric in wall thickness (shimmed) may compensate for drive asymmetries and improve implosion symmetry. Simulations suggest that for high compression implosions Legendre mode P 4 hohlraum flux asymmetries are the most detrimental to implosion performance. General Atomics has developed a diamond turning method to form a GDP capsule outer surface to a Legendre mode P 4 profile. The P 4 shape requiresmore » full capsule surface coverage. Thus, in order to avoid tool-lathe interference flipping the capsule part way through the machining process is required. This flipping process risks misalignment of the capsule causing a vertical step feature on the capsule surface. Recent trials have proven this step feature height can be minimized to ~0.25 µm.« less

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

NASA Astrophysics Data System (ADS)

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.

2015-11-01

In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ˜600 kA with ˜200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.

In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less

Validating Inertial Confinement Fusion (ICF) predictive capability using perturbed capsules

NASA Astrophysics Data System (ADS)

Schmitt, Mark; Magelssen, Glenn; Tregillis, Ian; Hsu, Scott; Bradley, Paul; Dodd, Evan; Cobble, James; Flippo, Kirk; Offerman, Dustin; Obrey, Kimberly; Wang, Yi-Ming; Watt, Robert; Wilke, Mark; Wysocki, Frederick; Batha, Steven

2009-11-01

Achieving ignition on NIF is a monumental step on the path toward utilizing fusion as a controlled energy source. Obtaining robust ignition requires accurate ICF models to predict the degradation of ignition caused by heterogeneities in capsule construction and irradiation. LANL has embarked on a project to induce controlled defects in capsules to validate our ability to predict their effects on fusion burn. These efforts include the validation of feature-driven hydrodynamics and mix in a convergent geometry. This capability is needed to determine the performance of capsules imploded under less-than-optimum conditions on future IFE facilities. LANL's recently initiated Defect Implosion Experiments (DIME) conducted at Rochester's Omega facility are providing input for these efforts. Recent simulation and experimental results will be shown.

Analysis of BigFoot HDC SymCap experiment N161205 on NIF

NASA Astrophysics Data System (ADS)

Dittrich, T. R.; Baker, K. L.; Thomas, C. A.; Berzak Hopkins, L. F.; Harte, J. A.; Zimmerman, G. B.; Woods, D. T.; Kritcher, A. L.; Ho, D. D.; Weber, C. R.; Kyrala, G.

2017-10-01

Analysis of NIF implosion experiment N161205 provides insight into both hohlraum and capsule performance. This experiment used an undoped High Density Carbon (HDC) ablator driven by a BigFoot x-ray profile in a Au hohlraum. Observations from this experiment include DT fusion yield, bang time, DSR, Tion and time-resolved x-ray emission images around bang time. These observations are all consistent with an x-ray spectrum having significantly reduced Au m-band emission that is present in a standard hohlraum simulation. Attempts to justify the observations using several other simulation modifications will be presented. This work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

Collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet

NASA Astrophysics Data System (ADS)

Espinosa, G.; Gil, J. M.; Rodriguez, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Suzuki-Vidal, F.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G.; Pickworth, L. A.; Skidmore, J.

2015-12-01

A computational investigation based on collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet is presented. The jet, both in vacuum and in argon ambient gas, was produced on the MAGPIE (Mega Ampere Generator for Plasma Implosion Experiments) generator and is formed by ablation of an aluminum foil driven by a 1.4 MA, 250 ns current pulse in a radial foil Z-pinch configuration. In this work, population kinetics and radiative properties simulations of the jet in different theoretical approximations were performed. In particular, local thermodynamic equilibrium (LTE), non-LTE steady state (SS) and non-LTE time dependent (TD) models have been considered. This study allows us to make a convenient microscopic characterization of the aluminum plasma jet.

X-ray source development for EXAFS measurements on the National Ignition Facility.

PubMed

Coppari, F; Thorn, D B; Kemp, G E; Craxton, R S; Garcia, E M; Ping, Y; Eggert, J H; Schneider, M B

2017-08-01

Extended X-ray absorption Fine Structure (EXAFS) measurements require a bright, spectrally smooth, and broad-band x-ray source. In a laser facility, such an x-ray source can be generated by a laser-driven capsule implosion. In order to optimize the x-ray emission, different capsule types and laser irradiations have been tested at the National Ignition Facility (NIF). A crystal spectrometer is used to disperse the x-rays and high efficiency image plate detectors are used to measure the absorption spectra in transmission geometry. EXAFS measurements at the K-edge of iron at ambient conditions have been obtained for the first time on the NIF laser, and the requirements for optimization have been established.

First beryllium capsule implosions on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kline, J. L.; Yi, S. A.; Simakov, A. N.

2016-05-15

The first indirect drive implosion experiments using Beryllium (Be) capsules at the National Ignition Facility confirm the superior ablation properties and elucidate possible Be-ablator issues such as hohlraum filling by ablator material. Since the 1990s, Be has been the preferred Inertial Confinement Fusion (ICF) ablator because of its higher mass ablation rate compared to that of carbon-based ablators. This enables ICF target designs with higher implosion velocities at lower radiation temperatures and improved hydrodynamic stability through greater ablative stabilization. Recent experiments to demonstrate the viability of Be ablator target designs measured the backscattered laser energy, capsule implosion velocity, core implosionmore » shape from self-emission, and in-flight capsule shape from backlit imaging. The laser backscatter is similar to that from comparable plastic (CH) targets under the same hohlraum conditions. Implosion velocity measurements from backlit streaked radiography show that laser energy coupling to the hohlraum wall is comparable to plastic ablators. The measured implosion shape indicates no significant reduction of laser energy from the inner laser cone beams reaching the hohlraum wall as compared with plastic and high-density carbon ablators. These results indicate that the high mass ablation rate for beryllium capsules does not significantly alter hohlraum energetics. In addition, these data, together with data for low fill-density hohlraum performance, indicate that laser power multipliers, required to reconcile simulations with experimental observations, are likely due to our limited understanding of the hohlraum rather than the capsule physics since similar multipliers are needed for both Be and CH capsules as seen in experiments.« less

Implosion dynamics of a megampere wire-array Z-pinch with an inner low-density foam shell at the Angara-5-1 facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V.; Bolkhovitinov, E. A.; Volkov, G. S., E-mail: volkov@triniti.ru

The implosion dynamics of a pinch with a highly inhomogeneous initial axial distribution of the load mass was studied experimentally. A cascade array consisting of a double nested tungsten wire array and a coaxial inner cylindrical shell located symmetrically with respect to the high-voltage electrodes was used as a load of the Angara-5-1 high-current generator. The cylindrical foam shell was half as long as the cathode− anode gap, and its diameter was equal to the diameter of the inner wire array. It is shown experimentally that two stages are typical of the implosion dynamics of such a load: the formationmore » of two separate pinches formed as a result of implosion of the wire array near the cathode and anode and the subsequent implosion of the central part of the load containing the cylindrical foam shell. The conditions are determined at which the implosion of the central part of the pinch with the foam cylinder is preceded by intense irradiation of the foam with the soft X-ray (SXR) emission generated by the near-electrode pinches and converting it into the plasma state. Using such a load, which models the main elements of the scheme of a dynamic hohlraum for inertial confinement fusion, it is possible to increase the efficiency of interaction between the outer accelerated plasma sheath and the inner foam shell by preionizing the foam with the SXR emission of the near-electrode pinches.« less

First beryllium capsule implosions on the National Ignition Facility

DOE PAGES

Kline, J. L.; Yi, S. A.; Simakov, A. N.; ...

2016-05-01

The first indirect drive implosion experiments using Beryllium (Be) capsules at the National Ignition Facility confirm the superior ablation properties and elucidate possible Be-ablator issues such as hohlraum filling by ablator material. Since the 1990s, Be has been the preferred Inertial Confinement Fusion (ICF) ablator because of its higher mass ablation rate compared to that of carbon-based ablators. This enables ICF target designs with higher implosion velocities at lower radiation temperatures and improved hydrodynamic stability through greater ablative stabilization. Recent experiments to demonstrate the viability of Be ablator target designs measured the backscattered laser energy, capsule implosion velocity, core implosionmore » shape from self-emission, and in-flight capsule shape from backlit imaging. The laser backscatter is similar to that from comparable plastic (CH) targets under the same hohlraum conditions. Implosion velocity measurements from backlit streaked radiography show that laser energy coupling to the hohlraum wall is comparable to plastic ablators. The measured implosion shape indicates no significant reduction of laser energy from the inner laser cone beams reaching the hohlraum wall as compared with plastic and high-density carbon ablators. These results indicate that the high mass ablation rate for beryllium capsules does not significantly alter hohlraum energetics. In addition, these data, together with data for low fill-density hohlraum performance, indicate that laser power multipliers, required to reconcile simulations with experimental observations, are likely due to our limited understanding of the hohlraum rather than the capsule physics since similar multipliers are needed for both Be and CH capsules as seen in experiments.« less

BOOK REVIEW: Inertial confinement fusion: The quest for ignition and energy gain using indirect drive

NASA Astrophysics Data System (ADS)

Yamanaka, C.

1999-06-01

Inertial confinement fusion (ICF) is an alternative way to control fusion which is based on scaling down a thermonuclear explosion to a small size, applicable for power production, a kind of thermonuclear internal combustion engine. This book extends many interesting topics concerning the research and development on ICF of the last 25 years. It provides a systematic development of the physics basis and also various experimental data on radiation driven implosion. This is a landmark treatise presented at the right time. It is based on the article ``Development of the indirect-drive approach to inertial confinement fusion and the target physics basis for ignition and gain'' by J.D. Lindl, published in Physics of Plasmas, Vol. 2, November 1995, pp. 3933-4024. As is well known, in the United States of America research on the target physics basis for indirect drive remained largely classified until 1994. The indirect drive approaches were closely related to nuclear weapons research at Lawrence Livermore and Los Alamos National Laboratories. In Japan and other countries, inertial confinement fusion research for civil energy has been successfully performed to achieve DT fuel pellet compression up to 1000 times normal density, and indirect drive concepts, such as the `Cannon Ball' scheme, also prevailed at several international conferences. In these circumstances the international fusion community proposed the Madrid Manifesto in 1988, which urged openness of ICF information to promote international collaboration on civil energy research for the future resources of the human race. This proposal was also supported by some of the US scientists. The United States Department of Energy revised its classification guidelines for ICF six years after the Madrid Manifesto. This first book from the USA treating target physics issues, covering topics from implosion dynamics to hydrodynamic stability, ignition physics, high-gain target design and the scope for energy applications is enthusiastically welcomed. The author joined Lawrence Livermore National Laboratory in 1972 to perform intensive theoretical and computational research on implosion and ignition. He was awarded the Edward Teller Medal in 1993. One therefore expects the topics to be treated with authority, and this expectation is well fulfilled. The general treatment throughout the book is to begin with the basic physics of implosion and show how its development leads to an explanation of many fundamental ideas about implosion, via direct drive or indirect drive, particularly ideas associated with radiation transport. This approach is generally successful, with the reader immediately able to relate the theoretical treatments to physical problems. One danger in this approach, however, is that fundamental concepts in implosion often become stressed within the framework of indirect radiation drive of hohlraum targets oriented towards research in the National Ignition Facility. The references in this book to Livermore or Los Alamos internal documents are not yet publicly available, because many are in the process of review for declassification. The reader will have to become accustomed to this situation, which has lasted for a long time but now seems to be gradually improving. The treatise is composed of 13 chapters, including 271 illustrations. An overview of ICF and the historical development of indirect drive in the ICF programme are described in Chapters 1 and 2. Direct drive and indirect drive have different features. The choice of which to use is a very interesting issue. The former has a higher laser-target coupling efficiency but is less uniform in laser irradiation due to discrete beams of lasers. Beam smoothing techniques have a key role in direct drive. The indirect drive by soft X rays which are generated at the inner surface of a hohlraum can have a higher uniform irradiation to reduce the growth of perturbations due to Rayleigh-Taylor (RT) instabilities. The soft X ray drive has much higher ablation rates and is less sensitive to hot electron preheat. A potential disadvantage of indirect drive is the larger scale length of the plasma travelled by the laser beam from the inlet hole to the hohlraum wall. Parametric instabilities in hohlraums have problems because of energy loss and coupling. One of the most important issues for indirect drive is a radiation drive concept which is essentially independent of the driver, such as laser or particle beam. The historical progress of ICF in the USA mainly depended upon the resolution of the fusion database for weaponry. This was a reason to choose indirect drive as the main scheme. Several structures of hohlraum target are described which for a long time were closed to the public. As the minimum energy for ignition depends strongly on the achievable implosion velocity, a great deal of benefit is derived from operating at the highest possible hohlraum temperature and in-flight aspect ratio (IFAR). The conclusion of Chapters 3, 4 and 5 is that achieving an implosion velocity of 3 × 107cm/s with an IFAR-30 Fermi degenerated shell would require a minimum drive temperature of about 200 eV. The hydrodynamic instability, ignition threshold and capsule gain are discussed in Chapter 6. The RT hydrodynamic instability began at the upper limit of the IFAR and hence at the peak implosion velocity. The growth rate of the instability in the acceleration phase was found to be suppressed by the ablation flow at Osaka. Instability during the deceleration phase was primarily stabilized by electron conduction. The combined effects of acceleration, feed-through and deceleration show that the principal modes contributing to perturbations in the fuel have spherical harmonic mode numbers less than about 30-40. The higher modes are rapidly reduced by rarefaction. The lower modes are killed by so-called `fire polishing'. The target uniformity and irradiation uniformity are very effective at suppressing instabilities. The maximum number of e-foldings sets the upper limit of the implosion velocity. This gives the threshold energy of ignition. The minimum capsule energy for ignition for indirect drive is compared with Nuckoll's projections for direct drive. The estimation depends strongly upon the effects of hydrodynamic instability and symmetry in the compressed fuel volume. If the margin of energy is 2, the necessary capsule absorbed energy is about 90 kJ with a radiation temperature of 300 eV. The coupling between driver and capsule is 10-15%, and the driver energy is 0.6-0.9 MJ. The scaling laws for the capsule absorbed power, radius and pulse length with a certain IFAR are given. It is concluded (Chapter 6) that the optimum strategy for gain is operation at the minimum implosion velocity consistent with the desired capsule size and yield, because at the excess implosion velocity the capsules tend to ignite earlier than the optimal point in the compression process. The most crucial issues for the hohlraum target are the coupling efficiency and hohlraum radiation uniformity. Various kinds of devices for hohlraum structures and double cone irradiation schemes have been investigated. These technological developments are energetically described. The implosion symmetry reproducibility (Chapters 7 and 8) for the Precision Nova advanced system meets the requirement of 1% uniformity for ignition experiment time averaged flux. Combined tests of symmetry and hydrodynamic instability as well as the hohlraum plasma conditions estimating the simulated Brillouin scattering (SBS) and simulated Raman scattering (SRS) effects and their influence on the hot electron preheat are summarized in Chapters 9, 10 and 11. The tolerable fraction of hot electrons for keeping the DT fuel preheat at approximately the Fermi specific energy indicates that direct drive capsules are 3 to 4 times larger than the indirect drive capsules. As a conclusion, Chapters 12 and 13 are proudly devoted to the National Ignition Facility and ignition targets. The NIF has a 192 beam, frequency tripled Nd:glass laser system with routine target energies and powers of 1.8 MJ and 500 TW, appropriately pulse shaped. The 192 beams are clustered in groups of 4, so that there are effectively 8 spots in each of the inner cones, and 16 in the outer cones in the hohlraum. Each cluster of 4 beams combines to form an effective f/8 optic. Various kinds of target design are described, for instance, a baseline design 300 eV hohlraum capsule, which absorbs 1.35 MJ of light, an ignition point hydrocarbon (CH) capsule, which is aimed at determining the requirements for symmetry, stability and ignition, and a lower temperature 250 eV capsule with a beryllium ablator, which provides a trade-off between hydroinstabilities and laser-plasma effects. The NIF baseline capsule designs absorb 150 kJ, of which about 25 kJ ends up in the compressed fuel. The central temperature increases to 10 keV when the capsule produces 400 kJ. The fuel energy gain is about 16 at ignition, or when the alpha particle deposition is about 3 times the initial energy delivered to the compressed fuel. The NIF baseline targets are then expected to yield up to 15 MJ and a fuel gain of about 600. Estimates based on NOVA experiments and modelling indicate that SBS, SRS and other plasma hazard processes can be kept within acceptable limits. If these are not attained, the ultimate recourse is to increase the hohlraum size, reduce the laser intensity and reduce the drive temperature to that of the 250 eV design, which has significantly less plasma. The remaining uncertainties can be mitigated by changes in the target design. The author has confidence ignition will be achieved in NIF, which seems to be strongly supported by the Centurion-Halite underground nuclear experiments demonstrating the excellent performance and the basic feasibility of achieving high gain. He thoughtfully adds a comment that developments in direct drive have reached the point where this approach also looks quite promising. NIF will be able to shift rapidly ( <= 1 d) between indirect drive and direct drive. Finally, the short last chapter (Chapter 13) gives an overview on the greatest potential for future ICF power plants. In a book review, questions are usually asked about the readers the book is primarily intended for, whether the book is written at the appropriate level for those readers and whether there are other books that achieve similar objectives. The last section of the Preface states that this book provides an in-depth analysis of theoretical and experimental work on indirect drive ICF classified up to 1994, as well as work carried out throughout the world. It is intended to serve as a reference guide for researchers in the field. Each topic covered contains enough introductory material that the book can also be used at the graduate level by students or newly interested researchers. Most of the laser technology and diagnostic development are not covered at all. To this reviewer that statement is a succinct summary of what the book achieves. Working fusion physicists, particularly in ICF, will find the book to be both instructive and enjoyable. As a secondary market, the book could well be used as a text for a graduate course in laser plasma physics, although some parts are like review papers. As to which books cover some of the same material, W.L. Kruer published Physics of Laser Plasma Interactions (Addison-Wesley, Redwood City, CA, 1988), which is suitable as a textbook for graduate students and also for the plasma physicist in general and C. Yamanaka published Introduction to Laser Fusion (Harwood Academic, Chur, 1991), which is the only book treating implosion physics, lasers, target design and diagnostics prior to the USDOE's declassification. As for the Handbook of Plasma Physics series (edited by M.N. Rosenbluth and R.Z. Sagdeev), Vol. 3, Physics of Laser Plasma (edited by A.H. Rubenchik and S. Witkowski) (Elsevier Science, Amsterdam, 1991) comes to mind. However, this last book is larger, and covers somewhat diverse topics. The typography of the book presently under review is also much to be preferred. In summary, I would strongly recommend the book by Lindl to my colleagues in plasma physics, particularly to those engaged in ICF.

Typical examples of classical novae

NASA Technical Reports Server (NTRS)

Hack, Margherita; Selvelli, Pierluigi; Bianchini, Antonio; Duerbeck, Hilmar W.

1993-01-01

Because of the very complicated individualistic behavior of each nova, we think it necessary to review the observations of a few well-observed individuals. We have selected a few objects of different speed classes, which have been extensively observed. They are: V1500 Cygni 1975, a very fast nova; V603 Aql 1918, fast nova; CP Pup 1942, fast nova; GK Per 1901, fast nova; V 1668 Cyg 1979, moderately fast nova; FH Ser 1970, slow nova; DQ Her 1934, slow nova; T Aur 1891, slow nova; RR Pic 1925, slow nova; and HR Del 1967, very slow nova.

Typical examples of classical novae

NASA Astrophysics Data System (ADS)

Hack, Margherita; Selvelli, Pierluigi; Bianchini, Antonio; Duerbeck, Hilmar W.

1993-09-01

Because of the very complicated individualistic behavior of each nova, we think it necessary to review the observations of a few well-observed individuals. We have selected a few objects of different speed classes, which have been extensively observed. They are: V1500 Cygni 1975, a very fast nova; V603 Aql 1918, fast nova; CP Pup 1942, fast nova; GK Per 1901, fast nova; V 1668 Cyg 1979, moderately fast nova; FH Ser 1970, slow nova; DQ Her 1934, slow nova; T Aur 1891, slow nova; RR Pic 1925, slow nova; and HR Del 1967, very slow nova.

Systematic Versus Semantic Desensitization and Implosive Therapy: A Comparative Study

ERIC Educational Resources Information Center

Hekmat, Hamid

1973-01-01

In this study, both the semantic and systematic desensitization methods were found to be significantly more effective than the implosive therapy and the control treatments in the modification of phobic behavior among the college student population. (Author)

Low-adiabat rugby hohlraum experiments on the National Ignition Facility: Comparison with high-flux modeling and the potential for gas-wall interpenetration

NASA Astrophysics Data System (ADS)

Amendt, Peter; Ross, J. Steven; Milovich, Jose L.; Schneider, Marilyn; Storm, Erik; Callahan, Debra A.; Hinkel, Denise; Lasinski, Barbara; Meeker, Don; Michel, Pierre; Moody, John; Strozzi, David

2014-11-01

Rugby-shaped gold hohlraums driven by a nominal low-adiabat laser pulse shape have been tested on the National Ignition Facility. The rugby affords a higher coupling efficiency than a comparably sized cylinder hohlraum or, alternatively, improved drive symmetry and laser beam clearances for a larger hohlraum with similar cylinder wall area and laser energy. A first (large rugby hohlraum) shot at low energy (0.75 MJ) to test laser backscatter resulted in a moderately oblate CH capsule implosion, followed by a high energy shot (1.3 MJ) that gave a highly oblate compressed core according to both time-integrated and -resolved x-ray images. These implosions used low wavelength separation (1.0 Å) between the outer and inner cones to provide an alternative platform free of significant cross-beam energy transfer for simplified hohlraum dynamics. Post-shot 2- and 3-D radiation-hydrodynamic simulations using the high-flux model [M. D. Rosen et al., High Energy Density Phys. 7, 180 (2011)], however, give nearly round implosions for both shots, in striking contrast with observations. An analytic assessment of Rayleigh-Taylor hydrodynamic instability growth on the gold-helium gas-fill interface shows the potential for significant linear growth, saturation and transition to a highly nonlinear state. Candidate seeds for instability growth include laser speckle during the early-time laser picket episode in the presence of only partial temporal beam smoothing (1-D smoothing by spectral dispersion and polarization smoothing) and intensity modulations from quad-to-quad and beam overlap. Radiation-hydrodynamic 2-D simulations adapted to include a dynamic fall-line mix model across the unstable Au-He interface show good agreement with the observed implosion symmetry for both shots using an interface-to-fall-line penetration fraction of 100%. Physically, the potential development of an instability layer in a rugby hohlraum is tantamount to an enhanced wall motion leading to hindered inner-beam propagation, due largely to the confluence of rugby shape and low ray angles relative to the hohlraum symmetry axis. A significant inward pointing shift of 500 μm in the outer cones for the third (full energy) shot of the series was used to improve the inner-beam propagation, resulting in a nearly symmetric x-ray self-emission image of the compressed core and reduced sensitivity to mix. Comparatively low time-dependent symmetry swings were also measured, and a significantly lower hot electron fraction was measured for potentially favorable fuel adiabat control. The outer cone stimulated Brillouin scatter levels jumped significantly, but remedial measures such as the use of a boron dopant in the Au wall are planned. A continuing trend of delayed implosion times is found in rugby hohlraums, suggesting levels of unaccounted hohlraum energy (˜150-200 kJ) similar to what is inferred in cylinder hohlraums. A mix-based physical scenario is described, based on suppressed channel heat flux to the dense gold wall from a temperature-gradient reversal induced by a multispecies plasma lapse rate [P. Amendt, C. Bellei, and S. C. Wilks, Phys. Rev. Lett. 109, 075002 (2012)].

Implosive Therapy as a Treatment for Insomnia.

ERIC Educational Resources Information Center

Carrera, Richard N.; Elenewski, Jeffrey J.

1980-01-01

The death implosion produced a decrease in insomnia beyond the strong expectancy effects that resulted from all experimental treatments. The failure to observe changes in reported fear of death was attributed to subjects' anxiety-based reluctance to acknowledge openly such fear. (Author)

In-flight neutron spectra as an ICF diagnostic for implosion asymmetries

NASA Astrophysics Data System (ADS)

Cerjan, C.; Sayre, D. B.; Sepke, S. M.

2018-02-01

The yield and spectral shape of the neutrons produced during in-flight reactions provide stringent constraints upon the symmetry of the fully compressed fuel conditions in Inertial Confinement Fusion implosions. Neutron production from a specific deuterium gas-filled implosion is simulated in detail and compared with the experimental neutron spectra along two lines-of-sight. An approximate reactivity formulation is applied to obtain further insight into the underlying fuel configuration. This analysis suggests that the differences observed in the observed spectra correspond to angularly dependent triton velocity distributions created by an asymmetric plasma configuration.

Radio Observations as a Tool to Investigate Shocks and Asymmetries in Accreting White Dwarf Binaries

NASA Astrophysics Data System (ADS)

Weston, Jennifer H. S.

2016-07-01

This dissertation uses radio observations with the Karl G. Jansky Very Large Array (VLA) to investigate the mechanisms that power and shape accreting white dwarfs (WD) and their ejecta. We test the predictions of both simple spherical and steady-state radio emission models by examining nova V1723 Aql, nova V5589 Sgr, symbiotic CH Cyg, and two small surveys of symbiotic binaries. First, we highlight classical nova V1723 Aql with three years of radio observations alongside optical and X-ray observations. We use these observations to show that multiple outflows from the system collided to create early non-thermal shocks with a brightness temperature of ≥106 K. While the late-time radio light curve is roughly consistent an expanding thermal shell of mass 2x10-4 M⊙ solar masses, resolved images of V1723 Aql show elongated material that apparently rotates its major axis over the course of 15 months, much like what is seen in gamma-ray producing nova V959 Mon, suggesting similar structures in the two systems. Next, we examine nova V5589 Sgr, where we find that the early radio emission is dominated by a shock-powered non-thermal flare that produces strong (kTx > 33 keV) X-rays. We additionally find roughly 10-5 M⊙ solar masses of thermal bremsstrahlung emitting material, all at a distance of ~4 kpc. The similarities in the evolution of both V1723 Aql and V5589 Sgr to that of nova V959 Mon suggest that these systems may all have dense equatorial tori shaping faster flows at their poles. Turning our focus to symbiotic binaries, we first use our radio observations of CH Cyg to link the ejection of a collimated jet to a change of state in the accretion disk. We additionally estimate the amount of mass ejected during this period (10-7 M⊙ masses), and improve measurements of the period of jet precession (P=12013 ± 74 days). We then use our survey of eleven accretion-driven symbiotic systems to determine that the radio brightness of a symbiotic system could potentially be used as an indicator of w hether a symbiotic is powered predominantly by shell burning on the surface of the WD or by accretion. We additionally make the first ever radio detections of seven of the targets in our survey. Our survey of seventeen radio bright symbiotics, comparing observations before and after the upgrades to the VLA, shows the technological feasibility to resolve the nebulae of nearby symbiotic binaries, opening the door for new lines of research. We spatially resolve extended structure in several symbiotic systems in radio for the first time. Additionally, our observations reveal extreme radio variability in symbiotic BF Cyg before and after the production of a jet from the system. Our results from our surveys of symbiotics provide some support for the model of radio emission where the red giant wind is photoionized by the WD, and suggests that there may be a greater population of radio faint, accretion driven symbiotic systems. This work emphasizes the powerful nature of radio observations as a tool for understanding eruptive WD binaries and their outflows.

Evolution of sausage and helical modes in magnetized thin-foil cylindrical liners driven by a Z-pinch

NASA Astrophysics Data System (ADS)

Yager-Elorriaga, D. A.; Lau, Y. Y.; Zhang, P.; Campbell, P. C.; Steiner, A. M.; Jordan, N. M.; McBride, R. D.; Gilgenbach, R. M.

2018-05-01

In this paper, we present experimental results on axially magnetized (Bz = 0.5 - 2.0 T), thin-foil (400 nm-thick) cylindrical liner-plasmas driven with ˜600 kA by the Michigan Accelerator for Inductive Z-Pinch Experiments, which is a linear transformer driver at the University of Michigan. We show that: (1) the applied axial magnetic field, irrespective of its direction (e.g., parallel or anti-parallel to the flow of current), reduces the instability amplitude for pure magnetohydrodynamic (MHD) modes [defined as modes devoid of the acceleration-driven magneto-Rayleigh-Taylor (MRT) instability]; (2) axially magnetized, imploding liners (where MHD modes couple to MRT) generate m = 1 or m = 2 helical modes that persist from the implosion to the subsequent explosion stage; (3) the merging of instability structures is a mechanism that enables the appearance of an exponential instability growth rate for a longer than expected time-period; and (4) an inverse cascade in both the axial and azimuthal wavenumbers, k and m, may be responsible for the final m = 2 helical structure observed in our experiments. These experiments are particularly relevant to the magnetized liner inertial fusion program pursued at Sandia National Laboratories, where helical instabilities have been observed.

The HEPCloud Facility: elastic computing for High Energy Physics – The NOvA Use Case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuess, S.; Garzoglio, G.; Holzman, B.

The need for computing in the HEP community follows cycles of peaks and valleys mainly driven by conference dates, accelerator shutdown, holiday schedules, and other factors. Because of this, the classical method of provisioning these resources at providing facilities has drawbacks such as potential overprovisioning. As the appetite for computing increases, however, so does the need to maximize cost efficiency by developing a model for dynamically provisioning resources only when needed. To address this issue, the HEPCloud project was launched by the Fermilab Scientific Computing Division in June 2015. Its goal is to develop a facility that provides a commonmore » interface to a variety of resources, including local clusters, grids, high performance computers, and community and commercial Clouds. Initially targeted experiments include CMS and NOvA, as well as other Fermilab stakeholders. In its first phase, the project has demonstrated the use of the “elastic” provisioning model offered by commercial clouds, such as Amazon Web Services. In this model, resources are rented and provisioned automatically over the Internet upon request. In January 2016, the project demonstrated the ability to increase the total amount of global CMS resources by 58,000 cores from 150,000 cores - a 25 percent increase - in preparation for the Recontres de Moriond. In March 2016, the NOvA experiment has also demonstrated resource burst capabilities with an additional 7,300 cores, achieving a scale almost four times as large as the local allocated resources and utilizing the local AWS s3 storage to optimize data handling operations and costs. NOvA was using the same familiar services used for local computations, such as data handling and job submission, in preparation for the Neutrino 2016 conference. In both cases, the cost was contained by the use of the Amazon Spot Instance Market and the Decision Engine, a HEPCloud component that aims at minimizing cost and job interruption. This paper describes the Fermilab HEPCloud Facility and the challenges overcome for the CMS and NOvA communities.« less

Progress Toward Ignition on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kauffman, R L

2011-10-17

The principal approach to ignition on the National Ignition Facility (NIF) is indirect drive. A schematic of an ignition target is shown in Figure 1. The laser beams are focused through laser entrance holes at each end of a high-Z cylindrical case, or hohlraum. The lasers irradiate the hohlraum walls producing x-rays that ablate and compress the fuel capsule in the center of the hohlraum. The hohlraum is made of Au, U, or other high-Z material. For ignition targets, the hohlraum is {approx}0.5 cm diameter by {approx}1 cm in length. The hohlraum absorbs the incident laser energy producing x-rays formore » symmetrically imploding the capsule. The fuel capsule is a {approx}2-mm-diameter spherical shell of CH, Be, or C filled with DT fuel. The DT fuel is in the form of a cryogenic layer on the inside of the capsule. X-rays ablate the outside of the capsule, producing a spherical implosion. The imploding shell stagnates in the center, igniting the DT fuel. NIC has overseen installation of all of the hardware for performing ignition experiments, including commissioning of approximately 50 diagnostic systems in NIF. The diagnostics measure scattered optical light, x-rays from the hohlraum over the energy range from 100 eV to 500 keV, and x-rays, neutrons, and charged particles from the implosion. An example of a diagnostic is the Magnetic Recoil Spectrometer (MRS) built by a collaboration of scientists from MIT, UR-LLE, and LLNL shown in Figure 2. MRS measures the neutron spectrum from the implosion, providing information on the neutron yield and areal density that are metrics of the quality of the implosion. Experiments on NIF extend ICF research to unexplored regimes in target physics. NIF can produce more than 50 times the laser energy and more than 20 times the power of any previous ICF facility. Ignition scale hohlraum targets are three to four times larger than targets used at smaller facilities, and the ignition drive pulses are two to five times longer. The larger targets and longer pulse lengths produce unique plasma conditions for laser-plasma instabilities that could reduce hohlraum coupling efficiency. Initial experiments have demonstrated efficient coupling of laser energy to x-rays. X-ray drive greater than 300 eV has been measured in gas-filled ignition hohlraum and shows the expected scaling with laser energy and hohlraum scale size. Experiments are now optimizing capsule implosions for ignition. Ignition conditions require assembling the fuel with sufficient density and temperature for thermonuclear burn. X-rays ablate the outside of the capsule, accelerating and spherically compressing the capsule for assembling the fuel. The implosion stagnates, heating the central core and producing a hot spot that ignites and burns the surrounding fuel. The four main characteristics of the implosion are shell velocity, central hot spot shape, fuel adiabat, and mix. Experiments studying these four characteristics of implosions are used to optimize the implosion. Integrated experiments using cryogenic fuel layer experiments demonstrate the quality of the implosion as the optimization experiments progress. The final compressed fuel conditions are diagnosed by measuring the x-ray emission from the hot core and the neutrons and charged particles produced in the fusion reactions. Metrics of the quality of the implosion are the neutron yield and the shell areal density, as well as the size and shape of the core. The yield depends on the amount of fuel in the hot core and its temperature and is a gauge of the energy coupling to the fuel. The areal density, the density of the fuel times its thickness, diagnoses the fuel assembly, which is measured using the fraction of neutrons that are down scattered passing through the dense shell. The yield and fraction of down scattered neutrons, or shell rho-r, from the cryogenic layered implosions are shown in Figure 3. The different sets of data represent results after a series of implosion optimization experiments. Both yield and areal density show significant increases as a result of the optimization. The experimental Ignition Threshold Factor (ITFX) is a measure of the progress toward ignition. ITFX is analogous to the Lawson Criterion in Magnetic Fusion. Implosions have improved by over a factor of 50 since the first cryogenic layered experiments were done in September 2010. This increase is a measure of the progress made toward the ignition goal in the past year. Optimization experiments are planned in the coming year for continued improvement in implosion performance to achieve the ignition goal. In summary, NIF has made significant progress toward ignition in the 30 months since project completion. Diagnostics and all of the supporting equipment are in place for ignition experiments. The Ignition Campaign is under way as a national collaborative effort of all the National Nuclear Security Administration (NNSA) science laboratories as well as international partners.« less

Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

DOE PAGES

Igumenshchev, I. V.; Goncharov, V. N.; Marshall, F. J.; ...

2016-05-04

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-dimension hydrodynamic simulations performed using a newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (~10 to 20 μm), and imperfect pointing, energy balance, and timing of the beams (with typical σ rms ~10 μm, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which a 880-μm-diameter capsule is illuminated by the same-diameter beams, and a “R75”more » design using a capsule of 900 μm in diameter and beams of 75% of this diameter. Simulations found that nonuniformities because of capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores resulting in an incomplete stagnation. The shape of distorted cores is well represented by neutron images, but loosely in x-rays. Simulated neutron spectra from perturbed implosions show large directional variations and up to ~ 2 keV variation of the hot spot temperature inferred from these spectra. The R75 design is more hydrodynamically efficient because of mitigation of crossed-beam energy transfer, but also suffers more from the nonuniformities. Furthermore, simulations predict a performance advantage of this design over the nominal design when the target offset and beam imbalance σ rms are reduced to less than 5 μm and 5%, respectively.« less

Detailed implosion modeling of deuterium-tritium layered experiments on the National Ignition Facilitya)

NASA Astrophysics Data System (ADS)

Clark, D. S.; Hinkel, D. E.; Eder, D. C.; Jones, O. S.; Haan, S. W.; Hammel, B. A.; Marinak, M. M.; Milovich, J. L.; Robey, H. F.; Suter, L. J.; Town, R. P. J.

2013-05-01

More than two dozen inertial confinement fusion ignition experiments with cryogenic deuterium-tritium layers have now been performed on the National Ignition Facility (NIF) [G. H. Miller et al., Opt. Eng. 443, 2841 (2004)]. Each of these yields a wealth of data including neutron yield, neutron down-scatter fraction, burn-averaged ion temperature, x-ray image shape and size, primary and down-scattered neutron image shape and size, etc. Compared to 2-D radiation-hydrodynamics simulations modeling both the hohlraum and the capsule implosion, however, the measured capsule yield is usually lower by a factor of 5 to 10, and the ion temperature varies from simulations, while most other observables are well matched between experiment and simulation. In an effort to understand this discrepancy, we perform detailed post-shot simulations of a subset of NIF implosion experiments. Using two-dimensional HYDRA simulations [M. M. Marinak, et al., Phys. Plasmas 8, 2275 (2001).] of the capsule only, these simulations represent as accurately as possible the conditions of a given experiment, including the as-shot capsule metrology, capsule surface roughness, and ice layer defects as seeds for the growth of hydrodynamic instabilities. The radiation drive used in these capsule-only simulations can be tuned to reproduce quite well the measured implosion timing, kinematics, and low-mode asymmetry. In order to simulate the experiments as accurately as possible, a limited number of fully three-dimensional implosion simulations are also being performed. Despite detailed efforts to incorporate all of the effects known and believed to be important in determining implosion performance, substantial yield discrepancies remain between experiment and simulation. Some possible alternate scenarios and effects that could resolve this discrepancy are discussed.

Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Igumenshchev, I. V.; Goncharov, V. N.; Marshall, F. J.

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-dimension hydrodynamic simulations performed using a newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (~10 to 20 μm), and imperfect pointing, energy balance, and timing of the beams (with typical σ rms ~10 μm, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which a 880-μm-diameter capsule is illuminated by the same-diameter beams, and a “R75”more » design using a capsule of 900 μm in diameter and beams of 75% of this diameter. Simulations found that nonuniformities because of capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores resulting in an incomplete stagnation. The shape of distorted cores is well represented by neutron images, but loosely in x-rays. Simulated neutron spectra from perturbed implosions show large directional variations and up to ~ 2 keV variation of the hot spot temperature inferred from these spectra. The R75 design is more hydrodynamically efficient because of mitigation of crossed-beam energy transfer, but also suffers more from the nonuniformities. Furthermore, simulations predict a performance advantage of this design over the nominal design when the target offset and beam imbalance σ rms are reduced to less than 5 μm and 5%, respectively.« less

Unique capabilities for ICF and HEDP research with the KrF laser

NASA Astrophysics Data System (ADS)

Obenschain, Stephen; Bates, Jason; Chan, Lop-Yung; Karasik, Max; Kehne, David; Sethian, John; Serlin, Victor; Weaver, James; Oh, Jaechul; Jenkins, Bruce; Lehmberg, Robert; Hegeler, Frank; Terrell, Stephen; Aglitskiy, Yefim; Schmitt, Andrew

2014-10-01

The krypton-fluoride (KrF) laser provides the shortest wavelength, broadest bandwidth and most uniform target illumination of all developed high-energy lasers. For directly driven targets these characteristics result in higher and more uniform ablation pressures as well as higher intensity thresholds for laser-plasma instability. The ISI beam smoothing scheme implemented on the NRL Nike KrF facility allows easy implementation of focal zooming where the laser radial profile is varied during the laser pulse. The capability for near continuous zooming with KrF would be valuable towards minimizing the effects of cross beam energy transport (CBET) in directly driven capsule implosions. The broad bandwidth ISI beam smoothing that is utilized with the Nike KrF facility may further inhibit certain laser plasma instability. In this presentation we will summarize our current understanding of laser target interaction with the KrF laser and the benefits it provides for ICF and certain HEDP experiments. Status and progress in high-energy KrF laser technology will also be discussed. Work supported by the Deparment of Energy, NNSA.

Observation of parametric instabilities in the quarter critical density region driven by the Nike KrF laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Phillips, L.; Afeyan, B.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S. P.; Serlin, V.; Schmitt, A. J.; Feldman, U.; Lehmberg, R. H.; Mclean, E.; Manka, C.

2013-02-01

The krypton-fluoride (KrF) laser is an attractive choice for inertial confinement fusion due to its combination of short wavelength (λ =248 nm), large bandwidth (up to 3 THz), and superior beam smoothing by induced spatial incoherence. These qualities improve the overall hydrodynamics of directly driven pellet implosions and should allow use of increased laser intensity due to higher thresholds for laser plasma instabilities when compared to frequency tripled Nd:glass lasers (λ =351 nm). Here, we report the first observations of the two-plasmon decay instability using a KrF laser. The experiments utilized the Nike laser facility to irradiate solid plastic planar targets over a range of pulse lengths (0.35 ns≤τ≤1.25 ns) and intensities (up to 2×1015 W/cm2). Variation of the laser pulse created different combinations of electron temperature and electron density scale length. The observed onset of instability growth was consistent with the expected scaling that KrF lasers have a higher intensity threshold for instabilities in the quarter critical density region.

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

DOE PAGES

Haines, Brian Michael; Grim, Gary P.; Fincke, James R.; ...

2016-07-29

Here, we present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employmore » any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.« less

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haines, Brian M., E-mail: bmhaines@lanl.gov; Fincke, James R.; Shah, Rahul C.

We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ anymore » adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.« less

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haines, Brian Michael; Grim, Gary P.; Fincke, James R.

Here, we present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employmore » any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.« less

The US ICF Ignition Program and the Inertial Fusion Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindl, J D; Hammel, B A; Logan, B G

2003-07-02

There has been rapid progress in inertial fusion in the past few years. This progress spans the construction of ignition facilities, a wide range of target concepts, and the pursuit of integrated programs to develop fusion energy using lasers, ion beams and z-pinches. Two ignition facilities are under construction (NIF in the U.S. and LMJ in France) and both projects are progressing toward an initial experimental capability. The LIL prototype beamline for LMJ and the first 4 beams of NIF will be available for experiments in 2003. The full 192 beam capability of NIF will be available in 2009 andmore » ignition experiments are expected to begin shortly after that time. There is steady progress in the target science and target fabrication in preparation for indirect drive ignition experiments on NIF. Advanced target designs may lead to 5-10 times more yield than initial target designs. There has also been excellent progress on the science of ion beam and z-pinch driven indirect drive targets. Excellent progress on direct-drive targets has been obtained on the Omega laser at the University of Rochester. This includes improved performance of targets with a pulse shape predicted to result in reduced hydrodynamic instability. Rochester has also obtained encouraging results from initial cryogenic implosions. There is widespread interest in the science of fast ignition because of its potential for achieving higher target gain with lower driver energy and relaxed target fabrication requirements. Researchers from Osaka have achieved outstanding implosion and heating results from the Gekko XII Petawatt facility and implosions suitable for fast ignition have been tested on the Omega laser. A broad based program to develop lasers and ions beams for IFE is under way with excellent progress in drivers, chambers, target fabrication and target injection. KrF and Diode Pumped Solid-State lasers (DPSSL) are being developed in conjunction with drywall chambers and direct drive targets. Induction accelerators for heavy ions are being developed in conjunction with thick-liquid protected wall chambers and indirect-drive targets.« less

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

NASA Astrophysics Data System (ADS)

Haines, Brian M.; Grim, Gary P.; Fincke, James R.; Shah, Rahul C.; Forrest, Chad J.; Silverstein, Kevin; Marshall, Frederic J.; Boswell, Melissa; Fowler, Malcolm M.; Gore, Robert A.; Hayes-Sterbenz, Anna C.; Jungman, Gerard; Klein, Andreas; Rundberg, Robert S.; Steinkamp, Michael J.; Wilhelmy, Jerry B.

2016-07-01

We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a "CD Mixcap," is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.

NOVA2-mediated RNA regulation is required for axonal pathfinding during development.

PubMed

Saito, Yuhki; Miranda-Rottmann, Soledad; Ruggiu, Matteo; Park, Christopher Y; Fak, John J; Zhong, Ru; Duncan, Jeremy S; Fabella, Brian A; Junge, Harald J; Chen, Zhe; Araya, Roberto; Fritzsch, Bernd; Hudspeth, A J; Darnell, Robert B

2016-05-25

The neuron specific RNA-binding proteins NOVA1 and NOVA2 are highly homologous alternative splicing regulators. NOVA proteins regulate at least 700 alternative splicing events in vivo, yet relatively little is known about the biologic consequences of NOVA action and in particular about functional differences between NOVA1 and NOVA2. Transcriptome-wide searches for isoform-specific functions, using NOVA1 and NOVA2 specific HITS-CLIP and RNA-seq data from mouse cortex lacking either NOVA isoform, reveals that NOVA2 uniquely regulates alternative splicing events of a series of axon guidance related genes during cortical development. Corresponding axonal pathfinding defects were specific to NOVA2 deficiency: Nova2-/- but not Nova1-/- mice had agenesis of the corpus callosum, and axonal outgrowth defects specific to ventral motoneuron axons and efferent innervation of the cochlea. Thus we have discovered that NOVA2 uniquely regulates alternative splicing of a coordinate set of transcripts encoding key components in cortical, brainstem and spinal axon guidance/outgrowth pathways during neural differentiation, with severe functional consequences in vivo.

Design Options for the High-Foot Ignition Capsule Series on NIF

NASA Astrophysics Data System (ADS)

Dittrich, T. R.; Hurricane, O. A.; Berzak Hopkins, L. F.; Callahan, D. A.; Clark, D.; Doeppner, T.; Haan, S. W.; Hammel, B. A.; Harte, J. A.; Hinkel, D. E.; Ma, T.; Pak, A. E.; Park, H.-S.; Salmonson, J. D.; Weber, C. R.; Zimmerman, G. B.; Olson, R. E.; Kline, J. L.; Leeper, R. J.

2015-11-01

Several options exist for improving implosion performance in the High-Foot series of ignition capsules on NIF. One option is to modify the fill tube used to supply DT to the capsule. Simulations indicate that a gold-coated glass tube may reduce implosion hydro effects and allow fielding a larger diameter tube capable of supporting the capsule, eliminating the need for the nominal tent support. A second option adds a fourth shock to the implosion history. According to simulation, this extra shock improves fuel confinement and capsule performance. A third option studies the feasibility of holding the DT fuel in liquid form in a foam layer inside the shell. This ``wetted foam'' concept, advanced by Olson, has existed for several years and may allow some control over the convergence of the capsule during implosion. This work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

Techniques for Enhancing Implosion Performance on High-Foot Ignition Capsules on NIF

NASA Astrophysics Data System (ADS)

Dittrich, T. R.; Hurricane, O.; Berzak Hopkins, L. F.; Callahan, D. A.; Clark, D.; Haan, S. W.; Hinkel, D. E.; Ma, T.; Nikroo, A.; Pak, A. E.; Park, H. S.; Salmonson, J. D.; Weber, C. R.

2016-10-01

Two options that have the potential to improve implosion performance in the High-Foot series of ignition capsules on NIF will be presented. The first option explores changing the shape of the x-ray drive to include a 4th and even a 5th shock in the implosion. According to simulations, these extra shocks improve the configuration of the assembled fuel and lead to improved confinement and performance. A ``ramp compression'' between the foot of the drive and the main pulse is also investigated. The second option studies the effect of increasing the Si dopant in a thin-shell capsule. NIF shot N150211 produced relatively high fusion yield (7.6E15 neutrons) but may have suffered from shell burn through. Increasing the Si dopant may delay this burn through yet preserve high implosion velocity. This work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smalyuk, V. A.; Robey, H. F.; Casey, D. T.

Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. Here in the deceleration phase of implosions, several experimental platformsmore » were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.« less

Mix and hydrodynamic instabilities on NIF

NASA Astrophysics Data System (ADS)

Smalyuk, V. A.; Robey, H. F.; Casey, D. T.; Clark, D. S.; Döppner, T.; Haan, S. W.; Hammel, B. A.; MacPhee, A. G.; Martinez, D.; Milovich, J. L.; Peterson, J. L.; Pickworth, L.; Pino, J. E.; Raman, K.; Tipton, R.; Weber, C. R.; Baker, K. L.; Bachmann, B.; Berzak Hopkins, L. F.; Bond, E.; Caggiano, J. A.; Callahan, D. A.; Celliers, P. M.; Cerjan, C.; Dixit, S. N.; Edwards, M. J.; Felker, S.; Field, J. E.; Fittinghoff, D. N.; Gharibyan, N.; Grim, G. P.; Hamza, A. V.; Hatarik, R.; Hohenberger, M.; Hsing, W. W.; Hurricane, O. A.; Jancaitis, K. S.; Jones, O. S.; Khan, S.; Kroll, J. J.; Lafortune, K. N.; Landen, O. L.; Ma, T.; MacGowan, B. J.; Masse, L.; Moore, A. S.; Nagel, S. R.; Nikroo, A.; Pak, A.; Patel, P. K.; Remington, B. A.; Sayre, D. B.; Spears, B. K.; Stadermann, M.; Tommasini, R.; Widmayer, C. C.; Yeamans, C. B.; Crippen, J.; Farrell, M.; Giraldez, E.; Rice, N.; Wilde, C. H.; Volegov, P. L.; Gatu Johnson, M.

2017-06-01

Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.

Time history prediction of direct-drive implosions on the Omega facility

DOE PAGES

Laffite, S.; Bourgade, J. L.; Caillaud, T.; ...

2016-01-14

We present in this article direct-drive experiments that were carried out on the Omega facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Two different pulse shapes were tested in order to vary the implosion stability of the same target whose parameters, dimensions and composition, remained the same. The direct-drive configuration on the Omega facility allows the accurate time-resolvedmeasurement of the scattered light. We show that, provided the laser coupling is well controlled, the implosion time history, assessed by the “bang-time” and the shell trajectory measurements, can be predicted. This conclusion is independent on the pulse shape. Inmore » contrast, we show that the pulse shape affects the implosion stability, assessed by comparing the target performances between prediction and measurement. For the 1-ns square pulse, the measuredneutron number is about 80% of the prediction. Lastly, for the 2-step 2-ns pulse, we test here that this ratio falls to about 20%.« less

Capsule Shimming Developments for National Ignition Facility (NIF) Hohlraum Asymmetry Experiments

DOE PAGES

Rice, Neal G.; Vu, M.; Kong, C.; ...

2017-12-20

Capsule drive in National Ignition Facility (NIF) indirect drive implosions is generated by x-ray illumination from cylindrical hohlraums. The cylindrical hohlraum geometry is axially symmetric but not spherically symmetric causing capsule-fuel drive asymmetries. We hypothesize that fabricating capsules asymmetric in wall thickness (shimmed) may compensate for drive asymmetries and improve implosion symmetry. Simulations suggest that for high compression implosions Legendre mode P 4 hohlraum flux asymmetries are the most detrimental to implosion performance. General Atomics has developed a diamond turning method to form a GDP capsule outer surface to a Legendre mode P 4 profile. The P 4 shape requiresmore » full capsule surface coverage. Thus, in order to avoid tool-lathe interference flipping the capsule part way through the machining process is required. This flipping process risks misalignment of the capsule causing a vertical step feature on the capsule surface. Recent trials have proven this step feature height can be minimized to ~0.25 µm.« less

Measuring radial profiles of nuclear burn in ICF implosions at OMEGA and the NIF using proton emission imaging

NASA Astrophysics Data System (ADS)

Seguin, F. H.; Rinderknecht, H. G.; Rosenberg, M.; Zylstra, A.; Frenje, J.; Li, C. K.; Petrasso, R.; Marshall, F. J.; Sangster, T. C.; Hoffman, N. M.; Amendt, P. A.; Bellei, C.; Le Pape, S.; Wilks, S. C.

2014-10-01

Fusion reactions in ICF implosions of D3He-filled capsules produce 14.7-MeV D3He protons and 3-MeV DD protons. Measurements of the spatial distributions of the D3He and DD reactions are studied with a penumbral imaging system that utilizes a CR-39-based imaging detector to simultaneously record separate penumbral images of the two types of protons. Measured burn profiles are useful for studying implosion physics and provide a critical test for benchmarking simulations. Recent implosions at OMEGA of CD capsules containing 3He gas fill and SiO2 capsules containing low-pressure D3He gas were expected to have hollow D3He burn profiles (in the 3He-filled capsule, due to fuel-shell mix), but penumbral imaging showed that the reactions were centrally peaked due to enhanced ion diffusion. The imaging technique is to be implemented soon on the NIF. This work was supported in part by NLUF, DOE, and LLE.

Mix and hydrodynamic instabilities on NIF

DOE PAGES

Smalyuk, V. A.; Robey, H. F.; Casey, D. T.; ...

2017-06-01

Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. Here in the deceleration phase of implosions, several experimental platformsmore » were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.« less

Time history prediction of direct-drive implosions on the Omega facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laffite, S.; Bourgade, J. L.; Caillaud, T.

We present in this article direct-drive experiments that were carried out on the Omega facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Two different pulse shapes were tested in order to vary the implosion stability of the same target whose parameters, dimensions and composition, remained the same. The direct-drive configuration on the Omega facility allows the accurate time-resolvedmeasurement of the scattered light. We show that, provided the laser coupling is well controlled, the implosion time history, assessed by the “bang-time” and the shell trajectory measurements, can be predicted. This conclusion is independent on the pulse shape. Inmore » contrast, we show that the pulse shape affects the implosion stability, assessed by comparing the target performances between prediction and measurement. For the 1-ns square pulse, the measuredneutron number is about 80% of the prediction. Lastly, for the 2-step 2-ns pulse, we test here that this ratio falls to about 20%.« less

Time history prediction of direct-drive implosions on the Omega facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laffite, S.; Bourgade, J. L.; Caillaud, T.

We present in this article direct-drive experiments that were carried out on the Omega facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Two different pulse shapes were tested in order to vary the implosion stability of the same target whose parameters, dimensions and composition, remained the same. The direct-drive configuration on the Omega facility allows the accurate time-resolved measurement of the scattered light. We show that, provided the laser coupling is well controlled, the implosion time history, assessed by the “bang-time” and the shell trajectory measurements, can be predicted. This conclusion is independent on the pulse shape.more » In contrast, we show that the pulse shape affects the implosion stability, assessed by comparing the target performances between prediction and measurement. For the 1-ns square pulse, the measured neutron number is about 80% of the prediction. For the 2-step 2-ns pulse, we test here that this ratio falls to about 20%.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klem, Michael

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory seeks to achieve thermonuclear ignition through inertial confinement fusion. The accurate assessment of the performance of each implosion experiment is a crucial step. Here we report on work to derive a reliable electron temperature for the cryogenic deuteriumtritium implosions completed on the NIF using the xray signal from the Ross filter diagnostic. These Xrays are dominated by bremsstrahlung emission. By fitting the xray signal measured through each of the individual Ross filters, the source bremsstrahlung spectrum can be inferred, and an electron temperature of the implosion hot spot inferred.more » Currently, each filter is weighted equally in this analysis. We present work quantifying the errors with such a technique and the results from investigating the contribution of each filter to the overall accuracy of the temperature inference. Using this research, we also compare the inferred electron temperature against other measured implosion quantities to develop a more complete understanding of the hotspot physics.« less

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA.

PubMed

Regan, S P; Goncharov, V N; Igumenshchev, I V; Sangster, T C; Betti, R; Bose, A; Boehly, T R; Bonino, M J; Campbell, E M; Cao, D; Collins, T J B; Craxton, R S; Davis, A K; Delettrez, J A; Edgell, D H; Epstein, R; Forrest, C J; Frenje, J A; Froula, D H; Gatu Johnson, M; Glebov, V Yu; Harding, D R; Hohenberger, M; Hu, S X; Jacobs-Perkins, D; Janezic, R; Karasik, M; Keck, R L; Kelly, J H; Kessler, T J; Knauer, J P; Kosc, T Z; Loucks, S J; Marozas, J A; Marshall, F J; McCrory, R L; McKenty, P W; Meyerhofer, D D; Michel, D T; Myatt, J F; Obenschain, S P; Petrasso, R D; Radha, P B; Rice, B; Rosenberg, M J; Schmitt, A J; Schmitt, M J; Seka, W; Shmayda, W T; Shoup, M J; Shvydky, A; Skupsky, S; Solodov, A A; Stoeckl, C; Theobald, W; Ulreich, J; Wittman, M D; Woo, K M; Yaakobi, B; Zuegel, J D

2016-07-08

A record fuel hot-spot pressure P_{hs}=56±7  Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, 011201(R) (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.

Convergent ablation measurements with gas-filled rugby hohlraum on OMEGA

NASA Astrophysics Data System (ADS)

Casner, A.; Jalinaud, T.; Galmiche, D.

2016-03-01

Convergent ablation experiments with gas-filled rugby hohlraum were performed for the first time on the OMEGA laser facility. A time resolved 1D streaked radiography of capsule implosion is acquired in the direction perpendicular to hohlraum axis, whereas a 2D gated radiography is acquired at the same time along the hohlraum axis on a x-ray framing camera. The implosion trajectory has been measured for various kinds of uniformly doped ablators, including germanium-doped and silicon-doped polymers (CH), at two different doping fraction (2% and 4% at.). Our experiments aimed also at measuring the implosion performance of laminated capsules. A laminated ablator is constituted by thin alternate layers of un-doped and doped CH. It has been previously shown in planar geometry that laminated ablators could mitigate Rayleigh Taylor growth at ablation front. Our results confirm that the implosion of a capsule constituted with a uniform or laminated ablator behaves similarly, in accordance with post-shot simulations performed with the CEA hydrocode FCI2.

Analysis of time-resolved argon line spectra from OMEGA direct-drive implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florido, R.; Nagayama, T.; Mancini, R. C.

2008-10-15

We discuss the observation and data analysis of argon K-shell line spectra from argon-doped deuterium-filled OMEGA direct-drive implosion cores based on data recorded with two streaked crystal spectrometers. The targets were 870 {mu}m in diameter, 27 {mu}m wall thickness plastic shells filled with 20 atm of deuterium gas, and a tracer amount of argon for diagnostic purposes. The argon K-shell line spectrum is primarily emitted at the collapse of the implosion and its analysis provides a spectroscopic diagnostic of the core implosion conditions. The observed spectra includes the He{alpha}, Ly{alpha}, He{beta}, He{gamma}, Ly{beta}, and Ly{gamma} line emissions and their associatedmore » He- and Li-like satellites thus covering a broad photon energy range from 3100 to 4200 eV with a spectral resolution power of approximately 500. The data analysis relies on detailed atomic and spectral models that take into account nonequilibrium collisional-radiative atomic kinetics, Stark-broadened line shapes, and radiation transport calculations.« less

A reassessment study of multi-material-shell gas puff z-pinches as a pulsed neutron source on the sandia ZR

NASA Astrophysics Data System (ADS)

Chong, Y. K.; Velikovich, A. L.; Thornhil, J. W.; Giuliani, J. L.; Knapp, P.; Jennings, C.

2013-10-01

Over the last few years, numerous 1D and 2D MHD simulation studies of deuterium (D) based double-shell gas-puff Z-pinch implosions driven by the Sandia ZR accelerator have been carried out to assess the Z-pinch as a pulsed thermal fusion neutron source. In these studies, an ad-hoc time-dependent shunt impedance model was used within the external driving circuit model in order to account for the unresolved current loss in the MITL and the load. In this study, we incorporate an improved ZR circuit model recently formulated based on the recent Sandia argon gas-puff experiment circuit data into the multi-material version of the Mach +DDTCRE RMHD code. We reinvestigate the effects of multidimensional structure and nonuniform gradients as well as the outer- and inner-shell material interaction on the implosion physics and dynamics of both D-on-D and argon-on-D Z-pinch loads using the model. Then, we characterize the neutron production performance of the Z-pinch loads as a function of total mass, mass ratio and/or radius toward their optimization as a pulsed thernonuclear neutron source. Work supported by DOE/NNSA. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's NNSA under contract DE-AC04-94AL85000.

Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weilacher, F.; Radha, P. B.; Forrest, C.

Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium–tritium (D–T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. Here, it is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [T. R.more » Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D–D and D–T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D–D reaction, whereas they insignificantly influence the inferred D–T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. Finally, this code will continue to be used for post-processing detailed hydrodynamic simulations and interpreting observed neutron spectra in ICF implosions.« less

Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

DOE PAGES

Weilacher, F.; Radha, P. B.; Forrest, C.

2018-04-26

Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium–tritium (D–T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. Here, it is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [T. R.more » Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D–D and D–T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D–D reaction, whereas they insignificantly influence the inferred D–T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. Finally, this code will continue to be used for post-processing detailed hydrodynamic simulations and interpreting observed neutron spectra in ICF implosions.« less

Fast-Ion Spectrometry of ICF Implosions and Laser-Foil Experiments at the Omega and MTW Laser Facilities

NASA Astrophysics Data System (ADS)

Sinenian, Nareg

Fast ions generated from laser-plasma interactions (LPI) have been used to study inertial confinement fusion (ICF) implosions and laser-foil interactions. LPI, which vary in nature depending on the wavelength and intensity of the driver, generate hot electrons with temperatures ranging from tens to thousands of kilo-electron-volts. These electrons, which accelerate the ions measured in this work, can be either detrimental or essential to implosion performance depending on the ICF scheme employed. In direct-drive hot-spot ignition, hot electrons can preheat the fuel and raise the adiabat, potentially degrading compression in the implosion. The amount of preheat depends on the hot-electron source characteristics and the time duration over which electrons can deposit energy into the fuel. This time duration is prescribed by the evolution of a sheath that surrounds the implosion and traps electrons. Fast-ion measurements have been used to develop a circuit model that describes the time decay of the sheath voltage for typical OMEGA implosions. In the context of electron fast ignition, the produced fast ions are considered a loss channel that has been characterized for the first time. These ions have also been used as a diagnostic tool to infer the temperature of the hot electrons in fast-ignition experiments. It has also been shown that the hot-electron temperature scales with laser intensity as expected, but is enhanced by a factor of 2-3. This enhancement is possibly due to relativistic effects and leads to poor implosion performance. Finally, fast-ion generation by ultra-intense lasers has also been studied using planar targets. The mean and maximum energies of protons and heavy ions has been measured, and it has been shown that a two-temperature hot-electron distribution affects the energies of heavy ions and protons. This work is important for advanced fusion concepts that utilize ion beams and also has applications in medicine. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

A scheme for reducing deceleration-phase Rayleigh-Taylor growth in inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

2016-05-01

It is demonstrated that the growth of acceleration-phase instabilities in inertial confinement fusion implosions can be controlled, especially in the high-foot implosions [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility. However, the excessive growth of the deceleration-phase instabilities can still destroy the hot spot ignition. A scheme is proposed to retard the deceleration-phase Rayleigh-Taylor instability growth by shock collision near the waist of the inner shell surface. Two-dimensional radiation hydrodynamic simulations confirm the improved deceleration-phase hot spot stability properties without sacrificing the fuel compression.

Variable convergence liquid layer implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Zylstra, A. B.; Yi, S. A.; Haines, B. M.; Olson, R. E.; Leeper, R. J.; Braun, T.; Biener, J.; Kline, J. L.; Batha, S. H.; Berzak Hopkins, L.; Bhandarkar, S.; Bradley, P. A.; Crippen, J.; Farrell, M.; Fittinghoff, D.; Herrmann, H. W.; Huang, H.; Khan, S.; Kong, C.; Kozioziemski, B. J.; Kyrala, G. A.; Ma, T.; Meezan, N. B.; Merrill, F.; Nikroo, A.; Peterson, R. R.; Rice, N.; Sater, J. D.; Shah, R. C.; Stadermann, M.; Volegov, P.; Walters, C.; Wilson, D. C.

2018-05-01

Liquid layer implosions using the "wetted foam" technique, where the liquid fuel is wicked into a supporting foam, have been recently conducted on the National Ignition Facility for the first time [Olson et al., Phys. Rev. Lett. 117, 245001 (2016)]. We report on a series of wetted foam implosions where the convergence ratio was varied between 12 and 20. Reduced nuclear performance is observed as convergence ratio increases. 2-D radiation-hydrodynamics simulations accurately capture the performance at convergence ratios (CR) ˜ 12, but we observe a significant discrepancy at CR ˜ 20. This may be due to suppressed hot-spot formation or an anomalous energy loss mechanism.

A scheme for reducing deceleration-phase Rayleigh–Taylor growth in inertial confinement fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L. F., E-mail: wang-lifeng@iapcm.ac.cn; Ye, W. H.; Liu, Jie

It is demonstrated that the growth of acceleration-phase instabilities in inertial confinement fusion implosions can be controlled, especially in the high-foot implosions [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility. However, the excessive growth of the deceleration-phase instabilities can still destroy the hot spot ignition. A scheme is proposed to retard the deceleration-phase Rayleigh–Taylor instability growth by shock collision near the waist of the inner shell surface. Two-dimensional radiation hydrodynamic simulations confirm the improved deceleration-phase hot spot stability properties without sacrificing the fuel compression.

Simulation and assessment of ion kinetic effects in a direct-drive capsule implosion experiment

DOE PAGES

Le, Ari Yitzchak; Kwan, Thomas J. T.; Schmitt, Mark J.; ...

2016-10-24

The first simulations employing a kinetic treatment of both fuel and shell ions to model inertial confinement fusion experiments are presented, including results showing the importance of kinetic physics processes in altering fusion burn. A pair of direct drive capsule implosions performed at the OMEGA facility with two different gas fills of deuterium, tritium, and helium-3 are analyzed. During implosion shock convergence, highly non-Maxwellian ion velocity distributions and separations in the density and temperature amongst the ion species are observed. Finally, diffusion of fuel into the capsule shell is identified as a principal process that degrades fusion burn performance.

Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive

DOE PAGES

Casey, D. T.; Milovich, J. L.; Smalyuk, V. A.; ...

2015-09-01

Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR > 1 g=cm 2. This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.

Assessment of the impact that the capsule fill tube has on implosions conducted with high density carbon ablators

NASA Astrophysics Data System (ADS)

Pak, Arthur; Benedetti, L. R.; Berzak Hopkins, L. F.; Clark, D.; Divol, L.; Dewald, E. L.; Fittinghoff, D.; Izumi, N.; Khan, S. F.; Landen, O.; Lepape, S.; Ma, T.; Marley, E.; Nagel, S.; Volegov, P.; Weber, C.; Bradley, D. K.; Callahan, D.; Grim, G.; Hurricane, O. A.; Patel, P.; Schneider, M. B.; Edwards, M. J.

2017-10-01

In recent inertial confinement implosion experiments conducted at the National Ignition Facility, bright and spatially localized x-ray emission within the hot spot at stagnation has been observed. This emission is associated with higher Z ablator material that is injected into the hot spot by the hydrodynamic perturbation induced by the 5-10 um diameter capsule fill tube. The reactivity of the DT fuel and subsequent yield of the implosion are strongly dependent on the density, temperature, and confinement time achieved throughout the stagnation of the implosion. Radiative losses from higher Z ablator material that mixes into the hot spot as well as non-uniformities in the compression and confinement induced by the fill tube perturbation can degrade the yield of the implosion. This work will examine the impact to conditions at stagnation that results from the fill tube perturbation. This assessment will be based from a pair of experiments conducted with a high density carbon ablator where the only deliberate change was reduction in fill tube diameter from 10 to 5 um. An estimate of the radiative losses and impact on performance from ablator mix injected into the hot spot by the fill tube perturbation will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Dynamics of conical wire array Z-pinch implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.

2007-10-15

A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators--the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P.more » Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.« less

Validating Hydrodynamic Growth in National Ignition Facility Implosions

NASA Astrophysics Data System (ADS)

Peterson, J. Luc

2014-10-01

The hydrodynamic growth of capsule imperfections can threaten the success of inertial confinement fusion implosions. Therefore, it is important to design implosions that are robust to hydrodynamic instabilities. However, the numerical simulation of interacting Rayleigh-Taylor and Richtmyer-Meshkov growth in these implosions is sensitive to modeling uncertainties such as radiation drive and material equations of state, the effects of which are especially apparent at high mode number (small perturbation wavelength) and high convergence ratio (small capsule radius). A series of validation experiments were conducted at the National Ignition Facility to test the ability to model hydrodynamic growth in spherically converging ignition-relevant implosions. These experiments on the Hydro-Growth Radiography platform constituted direct measurements of the growth of pre-imposed imperfections up to Legendre mode 160 and a convergence ratio of greater than four using two different laser drives: a ``low-foot'' drive used during the National Ignition Campaign and a larger adiabat ``high-foot'' drive that is modeled to be relatively more robust to ablation front hydrodynamic growth. We will discuss these experiments and how their results compare to numerical simulations and analytic theories of hydrodynamic growth, as well as their implications for the modeling of future designs. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

NOVA2-mediated RNA regulation is required for axonal pathfinding during development

PubMed Central

Saito, Yuhki; Miranda-Rottmann, Soledad; Ruggiu, Matteo; Park, Christopher Y; Fak, John J; Zhong, Ru; Duncan, Jeremy S; Fabella, Brian A; Junge, Harald J; Chen, Zhe; Araya, Roberto; Fritzsch, Bernd; Hudspeth, A J; Darnell, Robert B

2016-01-01

The neuron specific RNA-binding proteins NOVA1 and NOVA2 are highly homologous alternative splicing regulators. NOVA proteins regulate at least 700 alternative splicing events in vivo, yet relatively little is known about the biologic consequences of NOVA action and in particular about functional differences between NOVA1 and NOVA2. Transcriptome-wide searches for isoform-specific functions, using NOVA1 and NOVA2 specific HITS-CLIP and RNA-seq data from mouse cortex lacking either NOVA isoform, reveals that NOVA2 uniquely regulates alternative splicing events of a series of axon guidance related genes during cortical development. Corresponding axonal pathfinding defects were specific to NOVA2 deficiency: Nova2-/- but not Nova1-/- mice had agenesis of the corpus callosum, and axonal outgrowth defects specific to ventral motoneuron axons and efferent innervation of the cochlea. Thus we have discovered that NOVA2 uniquely regulates alternative splicing of a coordinate set of transcripts encoding key components in cortical, brainstem and spinal axon guidance/outgrowth pathways during neural differentiation, with severe functional consequences in vivo. DOI: http://dx.doi.org/10.7554/eLife.14371.001 PMID:27223325

X-ray source development for EXAFS measurements on the National Ignition Facility

DOE PAGES

Coppari, F.; Thorn, D. B.; Kemp, G. E.; ...

2017-08-28

We present that extended X-ray absorption Fine Structure (EXAFS) measurements require a bright, spectrally smooth, and broad-band x-ray source. In a laser facility, such an x-ray source can be generated by a laser-driven capsule implosion. In order to optimize the x-ray emission, different capsule types and laser irradiations have been tested at the National Ignition Facility (NIF). A crystal spectrometer is used to disperse the x-rays and high efficiency image plate detectors are used to measure the absorption spectra in transmission geometry. Finally, EXAFS measurements at the K-edge of iron at ambient conditions have been obtained for the first timemore » on the NIF laser, and the requirements for optimization have been established.« less

Early-Time Symmetry Tuning in the Presence of Cross-Beam Energy Transfer in ICF Experiments on the National Ignition Facility

DOE PAGES

Dewald, E. L.; Milovich, J. L.; Michel, P.; ...

2013-12-01

At the National Ignition Facility (NIF) we have successfully tuned the early time (~2 ns) lowest order Legendre mode (P 2) of the incoming radiation drive asymmetry of indirectly driven ignition capsule implosions by varying the inner power cone fraction. The measured P 2/P 0 sensitivity vs come fraction is similar to calculations, but a significant -15 to -20% P 2/P 0 offset was observed. This can be explained by a considerable early time laser energy transfer from the outer to the inner beams during the laser burn-through of the Laser Entrance Hole (LEH) windows and hohlraum fill gas whenmore » the LEH plasma is still dense and relatively cold.« less

Radiation hardening of gated x-ray imagers for the National Ignition Facility (invited).

PubMed

Bell, P M; Bradley, D K; Kilkenny, J D; Conder, A; Cerjan, C; Hagmann, C; Hey, D; Izumi, N; Moody, J; Teruya, A; Celeste, J; Kimbrough, J; Khater, H; Eckart, M J; Ayers, J

2010-10-01

The National Ignition Facility will soon be producing x-ray flux and neutron yields higher than any produced in laser driven implosion experiments in the past. Even a non-igniting capsule will require x-ray imaging of near burning plasmas at 10(17) neutrons, requiring x-ray recording systems to work in more hostile conditions than we have encountered in past laser facilities. We will present modeling, experimental data and design concepts for x-ray imaging with electronic recording systems for this environment (ARIANE). A novel instrument, active readout in a nuclear environment, is described which uses the time-of-flight difference between the gated x-ray signal and the neutron which induces a background signal to increase the yield at which gated cameras can be used.

AT Cnc: A SECOND DWARF NOVA WITH A CLASSICAL NOVA SHELL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shara, Michael M.; Mizusawa, Trisha; Zurek, David

2012-10-20

We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented 'shell', 3 arcmin in diameter, surrounding the dwarf novamore » AT Cancri. This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae cannot be very rare. The shell geometry is suggestive of bipolar, conical ejection seen nearly pole-on. A spectrum of the brightest AT Cnc shell knot is similar to that of the ejecta of the classical nova GK Per, and of Z Cam, dominated by [N II] emission. Galaxy Evolution Explorer FUV imagery reveals a similar-sized, FUV-emitting shell. We determine a distance of 460 pc to AT Cnc, and an upper limit to its ejecta mass of {approx}5 Multiplication-Sign 10{sup -5} M {sub Sun }, typical of classical novae.« less

Increase in Blood-Brain Barrier Perrmeability, Oxidative Stress, and Activated Microglia in a Rat Model of Blast-Induced Traumatic Brain Injury

DTIC Science & Technology

2010-01-01

a critical role in the secondary it~ury process following TBI. In recent work, our coiJeagues demonstrated that, in both controlled cortical...Animals were then placed inco the end of the expansion chamber of an air-driven shock tube (2.5 ft com- pression chamber conn!:cted to a 15 ft expansion...Significance with A NOVA fo llowed by post hoc analysis (SNK) as follows: * P < 0.05. progression of neuropatho logical processes tha t could be relevant to

Variable convergence liquid layer implosions on the National Ignition Facility

DOE PAGES

Zylstra, A. B.; Yi, S. A.; Haines, B. M.; ...

2018-03-19

Liquid layer implosions using the “wetted foam” technique, where the liquid fuel is wicked into a supporting foam, have been recently conducted on the National Ignition Facility for the first time [Olson et al., Phys. Rev. Lett. 117, 245001 (2016)]. In this paper, we report on a series of wetted foam implosions where the convergence ratio was varied between 12 and 20. Reduced nuclear performance is observed as convergence ratio increases. 2-D radiation-hydrodynamics simulations accurately capture the performance at convergence ratios (CR) ~ 12, but we observe a significant discrepancy at CR ~ 20. Finally, this may be due tomore » suppressed hot-spot formation or an anomalous energy loss mechanism.« less

Variable convergence liquid layer implosions on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B.; Yi, S. A.; Haines, B. M.

Liquid layer implosions using the “wetted foam” technique, where the liquid fuel is wicked into a supporting foam, have been recently conducted on the National Ignition Facility for the first time [Olson et al., Phys. Rev. Lett. 117, 245001 (2016)]. In this paper, we report on a series of wetted foam implosions where the convergence ratio was varied between 12 and 20. Reduced nuclear performance is observed as convergence ratio increases. 2-D radiation-hydrodynamics simulations accurately capture the performance at convergence ratios (CR) ~ 12, but we observe a significant discrepancy at CR ~ 20. Finally, this may be due tomore » suppressed hot-spot formation or an anomalous energy loss mechanism.« less

Comparison of Three Methods of Reducing Test Anxiety: Systematic Desensitization, Implosive Therapy, and Study Counseling

ERIC Educational Resources Information Center

Cornish, Richard D.; Dilley, Josiah S.

1973-01-01

Systematic desensitization, implosive therapy, and study counseling have all been effective in reducing test anxiety. In addition, systematic desensitization has been compared to study counseling for effectiveness. This study compares all three methods and suggests that systematic desentization is more effective than the others, and that implosive…

Three-dimensional simulations of National Ignition Facility implosions: Insight into experimental observablesa)

NASA Astrophysics Data System (ADS)

Spears, Brian K.; Munro, David H.; Sepke, Scott; Caggiano, Joseph; Clark, Daniel; Hatarik, Robert; Kritcher, Andrea; Sayre, Daniel; Yeamans, Charles; Knauer, James; Hilsabeck, Terry; Kilkenny, Joe

2015-05-01

We simulate in 3D both the hydrodynamics and, simultaneously, the X-ray and neutron diagnostic signatures of National Ignition Facility (NIF) implosions. We apply asymmetric radiation drive to study the impact of low mode asymmetry on diagnostic observables. We examine X-ray and neutron images as well as neutron spectra for these perturbed implosions. The X-ray images show hot spot evolution on small length scales and short time scales, reflecting the incomplete stagnation seen in the simulation. The neutron images show surprising differences from the X-ray images. The neutron spectra provide additional measures of implosion asymmetry. Flow in the hot spot alters the neutron spectral peak, namely, the peak location and width. The changes in the width lead to a variation in the apparent temperature with viewing angle that signals underlying hot spot asymmetry. We compare our new expectations based on the simulated data with NIF data. We find that some recent cryogenic layered experiments show appreciable temperature anisotropy indicating residual flow in the hot spot. We also find some trends in the data that do not reflect our simulation and theoretical understanding.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Temporal, Mauro; Canaud, Benoit; Cayzac, Witold

The alpha-particle energy deposition mechanism modifies the ignition conditions of the thermonuclear Deuterium-Tritium fusion reactions, and constitutes a key issue in achieving high gain in Inertial Confinement Fusion implosions. One-dimensional hydrodynamic calculations have been performed with the code Multi-IFE to simulate the implosion of a capsule directly irradiated by a laser beam. The diffusion approximation for the alpha energy deposition has been used to optimize three laser profiles corresponding to different implosion velocities. A Monte-Carlo package has been included in Multi-IFE to calculate the alpha energy transport, and in this case the energy deposition uses both the LP and themore » BPS stopping power models. Homothetic transformations that maintain a constant implosion velocity have been used to map out the transition region between marginally-igniting and high-gain configurations. Furthermore, the results provided by the two models have been compared and it is found that – close to the ignition threshold – in order to produce the same fusion energy, the calculations performed with the BPS model require about 10% more invested energy with respect to the LP model.« less

Main drive optimization of a high-foot pulse shape in inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

2016-12-01

While progress towards hot-spot ignition has been made achieving an alpha-heating dominated state in high-foot implosion experiments [Hurricane et al., Nat. Phys. 12, 800 (2016)] on the National Ignition Facility, improvements are needed to increase the fuel compression for the enhancement of the neutron yield. A strategy is proposed to improve the fuel compression through the recompression of a shock/compression wave generated by the end of the main drive portion of a high-foot pulse shape. Two methods for the peak pulse recompression, namely, the decompression-and-recompression (DR) and simple recompression schemes, are investigated and compared. Radiation hydrodynamic simulations confirm that the peak pulse recompression can clearly improve fuel compression without significantly compromising the implosion stability. In particular, when the convergent DR shock is tuned to encounter the divergent shock from the capsule center at a suitable position, not only the neutron yield but also the stability of stagnating hot-spot can be noticeably improved, compared to the conventional high-foot implosions [Hurricane et al., Phys. Plasmas 21, 056314 (2014)].

Specific features of implosion of metallized fiber arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitrofanov, K. N., E-mail: mitrofan@triniti.ru; Aleksandrov, V. V.; Gritsuk, A. N.

2017-02-15

Implosion of metallized fiber arrays was studied experimentally at the Angara-5-1 facility. The use of such arrays makes it possible to investigate the production and implosion dynamics of plasmas of various metals (such as tin, indium, and bismuth) that were previously unavailable for such studies. The plasma production rates m-dot (in μg/(cm{sup 2} ns)) for different metals were determined and quantitatively compared. Varying the thickness of the metal layer deposited on kapron fibers (the total linear mass of the metal coating being maintained at the level of 220 μg/cm), the current and velocity of the plasma precursor were studied asmore » functions of the thickness of the metal coating. The strong difference in the rates of plasma production from the metal coating and kapron fibers results in the redistribution of the discharge current between the Z-pinch and the trailing fiber plasma. The outer boundary of the plasma produced from the metal coating is found to be stable against instabilities typical of the final stage of implosion of conventional wire arrays.« less

Capsule modeling of high foot implosion experiments on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, D. S.; Kritcher, A. L.; Milovich, J. L.

This study summarizes the results of detailed, capsule-only simulations of a set of high foot implosion experiments conducted on the National Ignition Facility (NIF). These experiments span a range of ablator thicknesses, laser powers, and laser energies, and modeling these experiments as a set is important to assess whether the simulation model can reproduce the trends seen experimentally as the implosion parameters were varied. Two-dimensional (2D) simulations have been run including a number of effects—both nominal and off-nominal—such as hohlraum radiation asymmetries, surface roughness, the capsule support tent, and hot electron pre-heat. Selected three-dimensional simulations have also been run tomore » assess the validity of the 2D axisymmetric approximation. As a composite, these simulations represent the current state of understanding of NIF high foot implosion performance using the best and most detailed computational model available. While the most detailed simulations show approximate agreement with the experimental data, it is evident that the model remains incomplete and further refinements are needed. Nevertheless, avenues for improved performance are clearly indicated.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weilacher, F.; Radha, P. B., E-mail: rbah@lle.rochester.edu; Collins, T. J. B.

Ongoing polar-direct-drive (PDD) implosions on the National Ignition Facility (NIF) [J. D. Lindl and E. I. Moses, Phys. Plasmas 18, 050901 (2011)] use existing NIF hardware, including indirect-drive phase plates. This limits the performance achievable in these implosions. Spot shapes are identified that significantly improve the uniformity of PDD NIF implosions; outer surface deviation is reduced by a factor of 7 at the end of the laser pulse and hot-spot distortion is reduced by a factor of 2 when the shell has converged by a factor of ∼10. As a result, the neutron yield increases by approximately a factor ofmore » 2. This set of laser spot shapes is a combination of circular and elliptical spots, along with elliptical spot shapes modulated by an additional higher-intensity ellipse offset from the center of the beam. This combination is motivated in this paper. It is also found that this improved implosion uniformity is obtained independent of the heat conduction model. This work indicates that significant improvement in performance can be obtained robustly with the proposed spot shapes.« less

Hydro-scaling of DT implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Patel, Pravesh; Spears, Brian; Clark, Dan

2017-10-01

Recent implosion experiments on the National Ignition Facility (NIF) exceed 50 kJ in fusion yield and exhibit yield amplifications of >2.5-3x due to alpha-particle self-heating of the hot-spot. Two methods to increase the yield are (i) to improve the implosion quality, or stagnation pressure, at fixed target scale (by increasing implosion velocity, reducing 3D effects, etc.), and (ii) to hydrodynamically scale the capsule and absorbed energy. In the latter case the stagnation pressure remains constant, but the yield-in the absence of alpha-heating-increases as Y S 4 . 5 , where the capsule radius is increased by S, and the absorbed energy by S3 . With alpha-heating the increase with scale is considerably stronger. We present projections in the performance of current DT experiments, and the extrapolations to ignition, based on applying hydro-scaling theory and accounting for the effect of alpha-heating. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Improved Understanding of Implosion Symmetry through New Experimental Techniques Connecting Hohlraum Dynamics with Laser Beam Deposition

NASA Astrophysics Data System (ADS)

Ralph, Joseph; Salmonson, Jay; Dewald, Eduard; Bachmann, Benjamin; Edwards, John; Graziani, Frank; Hurricane, Omar; Landen, Otto; Ma, Tammy; Masse, Laurent; MacLaren, Stephen; Meezan, Nathan; Moody, John; Parrilla, Nicholas; Pino, Jesse; Sacks, Ryan; Tipton, Robert

2017-10-01

Understanding what affects implosion symmetry has been a challenge for scientists designing indirect drive inertial confinement fusion experiments on the National Ignition Facility (NIF). New experimental techniques and data analysis have been employed aimed at improving our understanding of the relationship between hohlraum dynamics and implosion symmetry. Thin wall imaging data allows for time-resolved imaging of 10 keV Au l-band x-rays providing for the first time on the NIF, a spatially resolved measurement of laser deposition with time. In the work described here, we combine measurements from the thin wall imaging with time resolved views of the interior of the hohlraum. The measurements presented are compared to hydrodynamic simulations as well as simplified physics models. The goal of this work is to form a physical picture that better explains the relationship of the hohlraum dynamics and capsule ablator on laser beam propagation and implosion symmetry. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

First-principles equation of state of polystyrene and its effect on inertial confinement fusion implosions

DOE PAGES

Hu, S. X.; Collins, L. A.; Goncharov, V. N.; ...

2015-10-14

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. Thus, with first-principles calculations, we have investigated the extended EOS of CH over a wide range of plasma conditions (ρ = 0.1 to 100 g/cm 3 and T = 1,000 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 targetmore » implosions on OMEGA using the FPEOS table of CH have predicted ~5% reduction in implosion velocity and ~30% decrease in neutron yield in comparison with the usual SESAME simulations. This is attributed to 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 lights from ICF implosions.« less

First-principles equation of state of polystyrene and its effect on inertial confinement fusion implosions.

PubMed

Hu, S X; Collins, L A; Goncharov, V N; Kress, J D; McCrory, R L; Skupsky, S

2015-10-01

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.

Final Report. Grant DOE DE-FG02-04ER54768

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betti, Riccardo

The magnetized spherical implosion campaign funded by this grant is summarized in this progress report. The main goal of this grant was to improve the seed eld generator MIFEDS (Magneto- Inertial Fusion Energy Delivery System) on the OMEGA laser to enable experiments at high elds (> 8 T) and to carry out magnetized spherical implosion experiments to study the e ect of magnetic elds on the fusion yield. New experiments were carried out in the last budget period to study the e ect of higher elds and shaped laser pulses. These new experiments improved the magnetized implosion database and allowedmore » us to improve the con dence of our conclusions with respect to the e ect of magnetic elds on implosion performance. The main conclusion is that adding magnetic eld leads to a 30% higher neutron yield, but using seed magnetic eld higher than 8 T does not further increase the neutron yield. A further conclusion is that the yield enhancement due to the magnetic eld is approximately independent of the laser pulse shape.« less

Measurement of Hydrodynamic Growth near Peak Velocity in an Inertial Confinement Fusion Capsule Implosion using a Self-Radiography Technique

NASA Astrophysics Data System (ADS)

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; MacPhee, A. G.; Scott, H. A.; Robey, H. F.; Landen, O. L.; Barrios, M. A.; Regan, S. P.; Schneider, M. B.; Hoppe, M.; Kohut, T.; Holunga, D.; Walters, C.; Haid, B.; Dayton, M.

2016-07-01

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 μ m , 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.

Gas-filled Rugby hohlraum energetics and implosions experiments on OMEGA

NASA Astrophysics Data System (ADS)

Casner, Alexis; Philippe, F.; Tassin, V.; Seytor, P.; Monteil, M. C.; Villette, B.; Reverdin, C.

2010-11-01

Recent experiments [1,2] have validated the x-ray drive enhancement provided by rugby-shaped hohlraums over cylinders in the indirect drive (ID) approach to inertial confinement fusion (ICF). This class of hohlraum is the baseline design for the Laser Mégajoule program, is also applicable to the National Ignition Facility and could therefore benefit ID Inertial Fusion Energy studies. We have carried out a serie of energetics and implosions experiments with OMEGA ``scale 1'' rugby hohlraums [1,2]. For empty hohlraums these experiments provide complementary measurements of backscattered light along 42 cone, as well as detailed drive history. In the case of gas-filled rugby hohlraums we have also study implosion performance (symmetry, yield, bangtime, hotspot spectra...) using a high contrast shaped pulse leading to a different implosion regime and for a range of capsule convergence ratios. These results will be compared with FCI2 hydrocodes calculations and future experimental campaigns will be suggested. [4pt] [1] F. Philippe et al., Phys. Rev. Lett. 104, 035004 (2010). [0pt] [2] H. Robey et al., Phys. Plasnas 17, 056313 (2010).

Modeling of Low Feed-Through CD Mix Implosions

NASA Astrophysics Data System (ADS)

Pino, Jesse; MacLaren, Steven; Greenough, Jeff; Casey, Daniel; Dittrich, Tom; Kahn, Shahab; Kyrala, George; Ma, Tammy; Salmonson, Jay; Smalyuk, Vladimir; Tipton, Robert

2015-11-01

The CD Mix campaign previously demonstrated the use of nuclear diagnostics to study the mix of separated reactants in plastic capsule implosions at the National Ignition Facility. However, the previous implosions suffered from large instability growth seeded from perturbations on the outside of the capsule. Recently, the separated reactants technique has been applied to two platforms designed to minimize this feed-through and isolate local mix at the gas-ablator interface: the Two Shock (TS) and Adiabat-Shaped (AS) Platforms. Additionally, the background contamination of Deuterium in the gas has been greatly reduced, allowing for simultaneous observation of TT, DT, and DD neutrons, which respectively give information about core gas performance, gas-shell atomic mix, and heating of the shell. In this talk, we describe efforts to model these implosions using high-resolution 2D ARES simulations with both a Reynolds-Averaged Navier Stokes method and an enhanced diffusivity model. 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-674867.

Measurement of hydrodynamic growth near peak velocity in an inertial confinement fusion capsule implosion using a self-radiography technique

DOE PAGES

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; ...

2016-07-11

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 linesmore » 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. As a result, 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.« less

Capsule modeling of high foot implosion experiments on the National Ignition Facility

DOE PAGES

Clark, D. S.; Kritcher, A. L.; Milovich, J. L.; ...

2017-03-21

This study summarizes the results of detailed, capsule-only simulations of a set of high foot implosion experiments conducted on the National Ignition Facility (NIF). These experiments span a range of ablator thicknesses, laser powers, and laser energies, and modeling these experiments as a set is important to assess whether the simulation model can reproduce the trends seen experimentally as the implosion parameters were varied. Two-dimensional (2D) simulations have been run including a number of effects—both nominal and off-nominal—such as hohlraum radiation asymmetries, surface roughness, the capsule support tent, and hot electron pre-heat. Selected three-dimensional simulations have also been run tomore » assess the validity of the 2D axisymmetric approximation. As a composite, these simulations represent the current state of understanding of NIF high foot implosion performance using the best and most detailed computational model available. While the most detailed simulations show approximate agreement with the experimental data, it is evident that the model remains incomplete and further refinements are needed. Nevertheless, avenues for improved performance are clearly indicated.« less

Experiments on helical modes in magnetized thin foil-plasmas

NASA Astrophysics Data System (ADS)

Yager-Elorriaga, David

2017-10-01

This paper gives an in-depth experimental study of helical features on magnetized, ultrathin foil-plasmas driven by the 1-MA linear transformer driver at University of Michigan. Three types of cylindrical liner loads were designed to produce: (a) pure magneto-hydrodynamic (MHD) modes (defined as being void of the acceleration-driven magneto-Rayleigh-Taylor instability, MRT) using a non-imploding geometry, (b) pure kink modes using a non-imploding, kink-seeded geometry, and (c) MRT-MHD coupled modes in an unseeded, imploding geometry. For each configuration, we applied relatively small axial magnetic fields of Bz = 0.2-2.0 T (compared to peak azimuthal fields of 30-40 T). The resulting liner-plasmas and instabilities were imaged using 12-frame laser shadowgraphy and visible self-emission on a fast framing camera. The azimuthal mode number was carefully identified with a tracking algorithm of self-emission minima. Our experiments show that the helical structures are a manifestation of discrete eigenmodes. The pitch angle of the helix is simply m / kR , from implosion to explosion, where m, k, and R are the azimuthal mode number, axial wavenumber, and radius of the helical instability. Thus, the pitch angle increases (decreases) during implosion (explosion) as R becomes smaller (larger). We found that there are one, or at most two, discrete helical modes that arise for magnetized liners, with no apparent threshold on the applied Bz for the appearance of helical modes; increasing the axial magnetic field from zero to 0.5 T changes the relative weight between the m = 0 and m = 1 modes. Further increasing the applied axial magnetic fields yield higher m modes. Finally, the seeded kink instability overwhelms the intrinsic instability modes of the plasma. These results are corroborated with our analytic theory on the effects of radial acceleration on the classical sausage, kink, and higher m modes. Work supported by US DOE award DE-SC0012328, Sandia National Laboratories, and the National Science Foundation. D.Y.E. was supported by NSF fellowship Grant Number DGE 1256260. The fast framing camera was supported by a DURIP, AFOSR Grant FA9550-15-1-0419.

Block Ignition Inertial Confinement Fusion (ICF) with Condensed Matter Cluster Type Targets for p-B11 Powered Space Propulsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miley, George H.; Hora, H.; Badziak, J.

The use of laser-driven Inertial Confinement Fusion (ICF) for space propulsion has been the subject of several earlier conceptual design studies, (see: Orth, 1998; and other references therein). However, these studies were based on older ICF technology using either 'direct' or 'in-direct x-ray driven' type target irradiation. Important new directions have opened for laser ICF in recent years following the development of 'chirped' lasers capable of ultra short pulses with powers of TW up to few PW which leads to the concept of 'fast ignition (FI)' to achieve higher energy gains from target implosions. In a recent publication the authorsmore » showed that use of a modified type of FI, termed 'block ignition' (Miley et al., 2008), could meet many of the requirements anticipated (but not then available) by the designs of the Vehicle for Interplanetary Space Transport Applications (VISTA) ICF fusion propulsion ship (Orth, 2008) for deep space missions. Subsequently the first author devised and presented concepts for imbedding high density condensed matter 'clusters' of deuterium into the target to obtain ultra high local fusion reaction rates (Miley, 2008). Such rates are possible due to the high density of the clusters (over an order of magnitude above cryogenic deuterium). Once compressed by the implosion, the yet higher density gives an ultra high reaction rate over the cluster volume since the fusion rate is proportional to the square of the fuel density. Most recently, a new discovery discussed here indicates that the target matrix could be composed of B{sup 11} with proton clusters imbedded. This then makes p-B{sup 11} fusion practical, assuming all of the physics issues such as stability of the clusters during compression are resolved. Indeed, p-B{sup 11} power is ideal for fusion propulsion since it has a minimum of unwanted side products while giving most of the reaction energy to energetic alpha particles which can be directed into an exhaust (propulsion) nozzle. Power plants using p-B{sup 11} have been discussed for such applications before, but prior designs face formidable physics/technology issues, largely overcome with the present approach.« less

Multidimensional Analysis of Direct-Drive Plastic-Shell Implosions on OMEGA

NASA Astrophysics Data System (ADS)

Radha, P. B.

2004-11-01

Direct-drive implosions of plastic shells with the OMEGA laser are used as energy-scaled warm surrogates for ignition cryogenic targets designed for use on the National Ignition Facility. Plastic targets involve varying shell thickness (15 to 33 μm), fill pressures (3 to 15 atm), and shell adiabats. The multidimensional hydrodynamics code DRACO is used to evaluate the effects of capsule-surface roughness and illumination nonuniformities on target performance. These simulations indicate that shell stability during the acceleration phase plays a critical role in determining fusion yields. For shells that are thick enough to survive the Rayleigh--Taylor growth, target yields are significantly reduced by growth of the long (ℓ < 10) and intermediate modes (20 < ℓ < 50) occurring from single-beam laser nonuniformities. The neutron production rate for these thick shells truncates relative to one-dimensional (1-D) predictions. The neutron-rate curves for the thinner shells, however, have significantly lower amplitudes and widths closer to 1-D results, indicating shell breakup during the acceleration phase. The simulation results are consistent with experimental observations. Previously, the stability of plastic-shell implosions had been correlated to a static ``mix-width'' at the boundary of the gas and plastic pusher estimated using a variety of experimental observables and an assumption of spherical symmetry. Results of these 2-D simulations provide a comprehensive understanding of warm-target implosion dynamics without assumptions of spherical symmetry and serve to answer the question of the hydrodynamic surrogacy between these plastic-shell implosions and the cryogenic ignition designs.

Observing the Next Galactic Supernova with the NOvA Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasel, Justin A.; Sheshukov, Andrey; Habig, Alec

The next galactic core-collapse supernova will deliver a wealth of neutrinos which for the first time we are well-situated to measure. These explosions produce neutrinos with energies between 10 and 100 MeV over a period of tens of seconds. Galactic supernovae are relatively rare events, occurring with a frequency of just a few per century. It is therefore essential that all neutrino detectors capable of detecting these neutrinos are ready to trigger on this signal when it occurs. This poster describes a data-driven trigger which is designed to detect the neutrino signal from a galactic core-collapse supernova with the NOvAmore » detectors. The trigger analyzes 5ms blocks of detector activity and applies background rejection algorithms to detect the signal time structure over the background. This background reduction is an essential part of the process, as the NOvA detectors are designed to detect neutrinos from Fermilab's NuMI beam which have an average energy of 2GeV--well above the average energy of supernova neutrinos.« less

A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors.

PubMed

Waugh, C J; Rosenberg, M J; Zylstra, A B; Frenje, J A; Séguin, F H; Petrasso, R D; Glebov, V Yu; Sangster, T C; Stoeckl, C

2015-05-01

Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition, comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.

A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

DOE PAGES

Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.; ...

2015-05-27

Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.

Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waugh, C. J., E-mail: cjwaugh@mit.edu; Zylstra, A. B.; Frenje, J. A.

2015-05-15

Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

Hydro-instability growth of perturbation seeds from alternate capsule-support strategies in indirect-drive implosions on National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez, D. A.; Smalyuk, V. A.; MacPhee, A. G.

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). 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 wasmore » 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 perturbations have studied instability growth of 10-μm and 30-μm thick fill tubes to compare them with 30-nm thick tent perturbations at convergence ratios up to ~3. In other experiments, the perturbations from cantilevered fill tubes were measured and compared to the tent perturbations. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by 100 μm, 200 μm, and 300 μm from the capsule surfaces. Based on these experiments, 30-μm thick fill tubes and 300-μm offset cantilevered fill tubes were recommended for further tests using layered deuterium-tritium implosions. In conclusion, the effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments.« less

Hydro-instability growth of perturbation seeds from alternate capsule-support strategies in indirect-drive implosions on National Ignition Facility

DOE PAGES

Martinez, D. A.; Smalyuk, V. A.; MacPhee, A. G.; ...

2017-10-20

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). 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 wasmore » 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 perturbations have studied instability growth of 10-μm and 30-μm thick fill tubes to compare them with 30-nm thick tent perturbations at convergence ratios up to ~3. In other experiments, the perturbations from cantilevered fill tubes were measured and compared to the tent perturbations. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by 100 μm, 200 μm, and 300 μm from the capsule surfaces. Based on these experiments, 30-μm thick fill tubes and 300-μm offset cantilevered fill tubes were recommended for further tests using layered deuterium-tritium implosions. In conclusion, the effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments.« less

Hydro-instability growth of perturbation seeds from alternate capsule-support strategies in indirect-drive implosions on National Ignition Facility

NASA Astrophysics Data System (ADS)

Martinez, D. A.; Smalyuk, V. A.; MacPhee, A. G.; Milovich, J.; Casey, D. T.; Weber, C. R.; Robey, H. F.; Chen, K.-C.; Clark, D. S.; Crippen, J.; Farrell, M.; Felker, S.; Field, J. E.; Haan, S. W.; Hammel, B. A.; Hamza, A. V.; Stadermann, M.; Hsing, W. W.; Kroll, J. J.; Landen, O. L.; Nikroo, A.; Pickworth, L.; Rice, N.

2017-10-01

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 perturbations have studied instability growth of 10-μm and 30-μm thick fill tubes to compare them with 30-nm thick tent perturbations at convergence ratios up to ˜3. In other experiments, the perturbations from cantilevered fill tubes were measured and compared to the tent perturbations. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by 100 μm, 200 μm, and 300 μm from the capsule surfaces. Based on these experiments, 30-μm thick fill tubes and 300-μm offset cantilevered fill tubes were recommended for further tests using layered deuterium-tritium implosions. The effects of x-ray shadowing during the drive and oxygen-induced perturbations during target assembly produced additional seeds for instabilities and were also measured in these experiments.

Performance of beryllium targets with full-scale capsules in low-fill 6.72-mm hohlraums on the National Ignition Facility

DOE PAGES

Simakov, A. N.; Wilson, D. C.; Yi, S. A.; ...

2017-05-10

When used with 1.06-mm beryllium (Be) capsules on the National Ignition Facility, gold hohlraums with the inner diameter of 5.75 mm and helium gas fill density of 1.6 mg/cm 3 exhibit significant drive degradation due to laser energy backscatter (of order 14%–17%) and “missing” X-ray drive energy (about 32% during the main pulse). Also, hard to simulate cross-beam energy transfer (CBET) must be used to control the implosion symmetry. Larger, 6.72-mm hohlraums with fill densities ≤0.6 mg/cm 3 generally offer improved drive efficiency, reduced hot-electron preheat, and better control of the implosion symmetry without CBET. Recently, we carried out anmore » exploratory campaign to evaluate performance of 1.06-mm Be capsules in such hohlraums and determine optimal hohlraum parameters. Specifically, we performed in this paper a hohlraum fill-density scan with a three-shock, 9.5-ns laser pulse and found that an appropriate axial laser repointing and azimuthal outer-quad splitting resulted in significantly improved hohlraum energetics at fill densities ≤0.3 mg/cm 3 (with backscattered and “missing” energies being of about 5% and 23% of the total laser energy, respectively). The capsule shape at stagnation was slightly oblate and improved with lowering the fill density. We also performed an implosion with a lower-picket, 12.6-ns pulse at the hohlraum fill density of 0.15 mg/cm 3 to observe comparable hohlraum energetics (about 3% of backscattered and 27% of “missing” energy) but an even more oblate implosion shape. Finally, achieving symmetric implosions of 1.06-mm Be capsules in low-fill, 6.72-mm gold hohlraums with reasonably low-adiabat pulses may not be feasible. However, symmetric implosions have recently been successfully demonstrated in such hohlraums with 0.8-mm Be capsules.« less

A Hubble Space Telescope survey for novae in M87.I. light and color curves, spatial distributions, and the nova rate

DOE PAGES

Shara, Michael M.; Doyle, Trisha F.; Lauer, Tod R.; ...

2016-11-08

The Hubble Space Telescope has imaged the central part of M87 over a 10 week span, leading to the discovery of 32 classical novae (CNe) and nine fainter, likely very slow, and/or symbiotic novae. In this first paper of a series, we present the M87 nova finder charts, and the light and color curves of the novae. We demonstrate that the rise and decline times, and the colors of M87 novae are uncorrelated with each other and with position in the galaxy. The spatial distribution of the M87 novae follows the light of the galaxy, suggesting that novae accreted by M87 during cannibalistic episodes are well-mixed. Conservatively using only the 32 brightest CNe we derive a nova rate for M87:more » $${363}_{-45}^{+33}$$ novae yr –1. We also derive the luminosity-specific classical nova rate for this galaxy, which is $${7.88}_{-2.6}^{+2.3}\\,{\\mathrm{yr}}^{-1}/{10}^{10}\\,{L}_{\\odot }{,}_{K}$$. Both rates are 3–4 times higher than those reported for M87 in the past, and similarly higher than those reported for all other galaxies. As a result, we suggest that most previous ground-based surveys for novae in external galaxies, including M87, miss most faint, fast novae, and almost all slow novae near the centers of galaxies.« less

Study of Plasma Liner Driven Magnetized Target Fusion Via Advanced Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samulyak, Roman V.; Brookhaven National Lab.; Parks, Paul

The feasibility of the plasma liner driven Magnetized Target Fusion (MTF) via terascale numerical simulations will be assessed. In the MTF concept, a plasma liner, formed by merging of a number (60 or more) of radial, highly supersonic plasma jets, implodes on the target in the form of two compact plasma toroids, and compresses it to conditions of the fusion ignition. By avoiding major difficulties associated with both the traditional laser driven inertial confinement fusion and solid liner driven MTF, the plasma liner driven MTF potentially provides a low-cost and fast R&D path towards the demonstration of practical fusion energy.more » High fidelity numerical simulations of full nonlinear models associated with the plasma liner MTF using state-of-art numerical algorithms and terascale computing are necessary in order to resolve uncertainties and provide guidance for future experiments. At Stony Brook University, we have developed unique computational capabilities that ideally suite the MTF problem. The FronTier code, developed in collaboration with BNL and LANL under DOE funding including SciDAC for the simulation of 3D multi-material hydro and MHD flows, has beenbenchmarked and used for fundamental and engineering problems in energy science applications. We have performed 3D simulations of converging supersonic plasma jets, their merger and the formation of the plasma liner, and a study of the corresponding oblique shock problem. We have studied the implosion of the plasma liner on the magnetized plasma target by resolving Rayleigh-Taylor instabilities in 2D and 3D and other relevant physics and estimate thermodynamic conditions of the target at the moment of maximum compression and the hydrodynamic efficiency of the method.« less

Recurrent novae

NASA Technical Reports Server (NTRS)

Hack, Margherita; Selvelli, Pierluigi

1993-01-01

Recurrent novae seem to be a rather inhomogeneous group: T CrB is a binary with a M III companion; U Sco probably has a late dwarf as companion. Three are fast novae; two are slow novae. Some of them appear to have normal chemical composition; others may present He and CNO excess. Some present a mass-loss that is lower by two orders of magnitude than classical novae. However, our sample is too small for saying whether there are several classes of recurrent novae, which may be related to the various classes of classical novae, or whether the low mass-loss is a general property of the class or just a peculiarity of one member of the larger class of classical novae and recurrent novae.

The awakening of a classical nova from hibernation.

PubMed

Mróz, Przemek; Udalski, Andrzej; Pietrukowicz, Paweł; Szymański, Michał K; Soszyński, Igor; Wyrzykowski, Łukasz; Poleski, Radosław; Kozłowski, Szymon; Skowron, Jan; Ulaczyk, Krzysztof; Skowron, Dorota; Pawlak, Michał

2016-09-29

Cataclysmic variable stars-novae, dwarf novae, and nova-likes-are close binary systems consisting of a white dwarf star (the primary) that is accreting matter from a low-mass companion star (the secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of ten thousand to a million years. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a billionth of a solar mass per year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate in the binary, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for a thousand to a million years, starting the hibernation phase. After that the nova awakes again-with accretion returning to the pre-eruption level and leading to a new nova explosion. The hibernation model predicts cyclical evolution of cataclysmic variables through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around the dwarf novae Z Camelopardalis and AT Cancri, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Here we report long-term observations of the classical nova V1213 Cen (Nova Centauri 2009) covering its pre- and post-eruption phases and precisely documenting its evolution. Within the six years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is two orders of magnitude brighter than the pre-nova at minimum light with no trace of dwarf nova behaviour, implying that the mass-transfer rate increased considerably as a result of the nova explosion.

The Masses and Accretion Rates of White Dwarfs in Classical and Recurrent Novae

NASA Astrophysics Data System (ADS)

Shara, Michael M.; Prialnik, Dina; Hillman, Yael; Kovetz, Attay

2018-06-01

Models have long predicted that the frequency-averaged masses of white dwarfs (WDs) in Galactic classical novae are twice as large as those of field WDs. Only a handful of dynamically well-determined nova WDs masses have been published, leaving the theoretical predictions poorly tested. The recurrence time distributions and mass accretion rate distributions of novae are even more poorly known. To address these deficiencies, we have combined our extensive simulations of nova eruptions with the Strope et al. and Schaefer databases of outburst characteristics of Galactic classical and recurrent novae (RNe) to determine the masses of 92 WDs in novae. We find that the mean mass (frequency-averaged mean mass) of 82 Galactic classical novae is 1.06 (1.13) M ⊙, while the mean mass of 10 RNe is 1.31 M ⊙. These masses, and the observed nova outburst amplitude and decline time distributions allow us to determine the long-term mass accretion rate distribution of classical novae. Remarkably, that value is just 1.3 × 10‑10 M ⊙ yr‑1, which is an order of magnitude smaller than that of cataclysmic binaries in the decades before and after classical nova eruptions. This predicts that old novae become low-mass transfer rate systems, and hence dwarf novae, for most of the time between nova eruptions. We determine the mass accretion rates of each of the 10 known Galactic recurrent nova, finding them to be in the range of 10‑7–10‑8 M ⊙ yr‑1. We are able to predict the recurrence time distribution of novae and compare it with the predictions of population synthesis models.

Evidence for Stratification of Deuterium-Tritium Fuel in Inertial Confinement Fusion Implosions

NASA Astrophysics Data System (ADS)

Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; Manuel, M. J.-E.; Rinderknecht, H. G.; Sinenian, N.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu; Meyerhofer, D. D.; Sangster, T. C.; McNabb, D. P.; Amendt, P. A.; Boyd, R. N.; Rygg, J. R.; Herrmann, H. W.; Kim, Y. H.; Bacher, A. D.

2012-02-01

Measurements of the D(d,p)T (dd) and T(t,2n)He4 (tt) reaction yields have been compared with those of the D(t,n)He4 (dt) reaction yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on the OMEGA laser, absolute spectral measurements of dd protons and tt neutrons were obtained. From these measurements, it was concluded that the dd yield is anomalously low and the tt yield is anomalously high relative to the dt yield, an observation that we conjecture to be caused by a stratification of the fuel in the implosion core. This effect may be present in ignition experiments planned on the National Ignition Facility.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility.

PubMed

Marozas, J A; Hohenberger, M; Rosenberg, M J; Turnbull, D; Collins, T J B; Radha, P B; McKenty, P W; Zuegel, J D; Marshall, F J; Regan, S P; Sangster, T C; Seka, W; Campbell, E M; Goncharov, V N; Bowers, M W; Di Nicola, J-M G; Erbert, G; MacGowan, B J; Pelz, L J; Yang, S T

2018-02-23

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  Å 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.

Evidence for stratification of deuterium-tritium fuel in inertial confinement fusion implosions.

PubMed

Casey, D T; Frenje, J A; Johnson, M Gatu; Manuel, M J-E; Rinderknecht, H G; Sinenian, N; Séguin, F H; Li, C K; Petrasso, R D; Radha, P B; Delettrez, J A; Glebov, V Yu; Meyerhofer, D D; Sangster, T C; McNabb, D P; Amendt, P A; Boyd, R N; Rygg, J R; Herrmann, H W; Kim, Y H; Bacher, A D

2012-02-17

Measurements of the D(d,p)T (dd) and T(t,2n)(4)He (tt) reaction yields have been compared with those of the D(t,n)(4)He (dt) reaction yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on the OMEGA laser, absolute spectral measurements of dd protons and tt neutrons were obtained. From these measurements, it was concluded that the dd yield is anomalously low and the tt yield is anomalously high relative to the dt yield, an observation that we conjecture to be caused by a stratification of the fuel in the implosion core. This effect may be present in ignition experiments planned on the National Ignition Facility.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; Turnbull, D.; Collins, T. J. B.; Radha, P. B.; McKenty, P. W.; Zuegel, J. D.; Marshall, F. J.; Regan, S. P.; Sangster, T. C.; Seka, W.; Campbell, E. M.; Goncharov, V. N.; Bowers, M. W.; Di Nicola, J.-M. G.; Erbert, G.; MacGowan, B. J.; Pelz, L. J.; Yang, S. T.

2018-02-01

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 Å 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.

A Hubble Space Telescope Survey for Novae in M87. I. Light and Color Curves, Spatial Distributions, and the Nova Rate

NASA Astrophysics Data System (ADS)

Shara, Michael M.; Doyle, Trisha F.; Lauer, Tod R.; Zurek, David; Neill, J. D.; Madrid, Juan P.; Mikołajewska, Joanna; Welch, D. L.; Baltz, Edward A.

2016-11-01

The Hubble Space Telescope has imaged the central part of M87 over a 10 week span, leading to the discovery of 32 classical novae (CNe) and nine fainter, likely very slow, and/or symbiotic novae. In this first paper of a series, we present the M87 nova finder charts, and the light and color curves of the novae. We demonstrate that the rise and decline times, and the colors of M87 novae are uncorrelated with each other and with position in the galaxy. The spatial distribution of the M87 novae follows the light of the galaxy, suggesting that novae accreted by M87 during cannibalistic episodes are well-mixed. Conservatively using only the 32 brightest CNe we derive a nova rate for M87: {363}-45+33 novae yr‑1. We also derive the luminosity-specific classical nova rate for this galaxy, which is {7.88}-2.6+2.3 {yr}}-1/{10}10 {L}ȯ {,}K. Both rates are 3–4 times higher than those reported for M87 in the past, and similarly higher than those reported for all other galaxies. We suggest that most previous ground-based surveys for novae in external galaxies, including M87, miss most faint, fast novae, and almost all slow novae near the centers of galaxies. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. Here, we propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method usesmore » a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT "clean" and DT "mix" gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. Furthermore, we observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λ ii~T 2/Z 2ρ at the gas/shell interface. Finally, since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.« less

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

DOE PAGES

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.; ...

2016-05-26

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. Here, we propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method usesmore » a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT "clean" and DT "mix" gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. Furthermore, we observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λ ii~T 2/Z 2ρ at the gas/shell interface. Finally, since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.« less

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.; McEvoy, A. M.; Zylstra, A.; Hammel, B. A.; Sepke, S. M.; Leatherland, A.; Gales, S.

2016-05-01

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. We propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method uses a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT “clean” and DT “mix” gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. An experiment to observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λii∼T2/Z2ρ at the gas/shell interface. Since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.

Axial magnetic field injection in magnetized liner inertial fusion

NASA Astrophysics Data System (ADS)

Gourdain, P.-A.; Adams, M. B.; Davies, J. R.; Seyler, C. E.

2017-10-01

MagLIF is a fusion concept using a Z-pinch implosion to reach thermonuclear fusion. In current experiments, the implosion is driven by the Z-machine using 19 MA of electrical current with a rise time of 100 ns. MagLIF requires an initial axial magnetic field of 30 T to reduce heat losses to the liner wall during compression and to confine alpha particles during fusion burn. This field is generated well before the current ramp starts and needs to penetrate the transmission lines of the pulsed-power generator, as well as the liner itself. Consequently, the axial field rise time must exceed hundreds of microseconds. Any coil capable of being submitted to such a field for that length of time is inevitably bulky. The space required to fit the coil near the liner, increases the inductance of the load. In turn, the total current delivered to the load decreases since the voltage is limited by driver design. Yet, the large amount of current provided by the Z-machine can be used to produce the required 30 T field by tilting the return current posts surrounding the liner, eliminating the need for a separate coil. However, the problem now is the field penetration time, across the liner wall. This paper discusses why skin effect arguments do not hold in the presence of resistivity gradients. Numerical simulations show that fields larger than 30 T can diffuse across the liner wall in less than 60 ns, demonstrating that external coils can be replaced by return current posts with optimal helicity.

The Galactic Nova Rate Revisited

NASA Astrophysics Data System (ADS)

Shafter, A. W.

2017-01-01

Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching m≤slant 2 to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae and by employing a Monte Carlo analysis to better estimate the uncertainty in the derived nova rates. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations and in the absolute magnitude distribution. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates of ˜50 to in excess of 100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of ˜35 to ˜75 per year. An average of the most plausible models yields a rate of {50}-23+31 yr-1, which is arguably the best estimate currently available for the nova rate in the Galaxy. Virtually all models produce rates that represent significant increases over recent estimates, and bring the Galactic nova rate into better agreement with that expected based on comparison with the latest results from extragalactic surveys.

Implosion-driven technique to create fast shockwaves in high-density gas

NASA Astrophysics Data System (ADS)

Serge, Matthew; Loiseau, Jason; Huneault, Justin; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent

2012-03-01

Pressurized tubes surrounded by either one or two layers (separated by a secondary tube) of sensitized nitromethane and encased in a thick-walled tube (the tamper) were imploded. The distance between the detonation wave in the explosive and shock wave in the innermost tube were measured (the standoff). A simple model based on hoop stress and acoustic interactions between the tubing was developed and used to predict the standoff distance. At low initial pressures (on the order of 7MPa), results indicate that the secondary tube and two layers of explosive did not prove to significantly increase the standoff. However, at higher pressures (on the order of 10 MPa), standoff was noticeably greater when the secondary tube was inserted between the pressurized tube and the tamper. The measured values are in reasonable agreement with the predictions of the model.

Observation of LPI Thresholds for the Nike Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Afeyan, B.; Charbonneau-Lefort, M.; Phillips, L.; Seely, J.; Kehne, D.; Brown, C.; Obenschain, S.; Schmitt, A. J.; Feldman, U.; Holland, G.; Lehmberg, R. H.; McLean, E.; Manka, C.

2008-11-01

The Nike laser is being used to study thresholds for laser plasma instabilities (LPI) at intensities (10^15-10^16 W/cm^2) relevant to advanced implosion designs for direct drive inertial confinement fusion. The combination of short wavelength (248 nm), large bandwidth (1-2 THz), and beam smoothing by induced spatial incoherence available with this krypton-fluoride laser make these experiments unique among current facilities. This talk will present an overview of results with an emphasis on the two-plasmon decay instability (2φp). Measurements of x-rays and emission near ^1/2φo and ^3/2 φo harmonics of the laser wavelength have been collected over a wide range of intensities for both solid and foam targets. Data indicate collective multiple-angle driven excitation compatible with previous observations using solid planar targets.

Proper-motion age dating of the progeny of Nova Scorpii AD 1437.

PubMed

Shara, M M; Iłkiewicz, K; Mikołajewska, J; Pagnotta, A; Bode, M F; Crause, L A; Drozd, K; Faherty, J; Fuentes-Morales, I; Grindlay, J E; Moffat, A F J; Pretorius, M L; Schmidtobreick, L; Stephenson, F R; Tappert, C; Zurek, D

2017-08-30

'Cataclysmic variables' are binary star systems in which one star of the pair is a white dwarf, and which often generate bright and energetic stellar outbursts. Classical novae are one type of outburst: when the white dwarf accretes enough matter from its companion, the resulting hydrogen-rich atmospheric envelope can host a runaway thermonuclear reaction that generates a rapid brightening. Achieving peak luminosities of up to one million times that of the Sun, all classical novae are recurrent, on timescales of months to millennia. During the century before and after an eruption, the 'novalike' binary systems that give rise to classical novae exhibit high rates of mass transfer to their white dwarfs. Another type of outburst is the dwarf nova: these occur in binaries that have stellar masses and periods indistinguishable from those of novalikes but much lower mass-transfer rates, when accretion-disk instabilities drop matter onto the white dwarfs. The co-existence at the same orbital period of novalike binaries and dwarf novae-which are identical but for their widely varying accretion rates-has been a longstanding puzzle. Here we report the recovery of the binary star underlying the classical nova eruption of 11 March AD 1437 (refs 12, 13), and independently confirm its age by proper-motion dating. We show that, almost 500 years after a classical-nova event, the system exhibited dwarf-nova eruptions. The three other oldest recovered classical novae display nova shells, but lack firm post-eruption ages, and are also dwarf novae at present. We conclude that many old novae become dwarf novae for part of the millennia between successive nova eruptions.

Novae as distance indicators

NASA Technical Reports Server (NTRS)

Ford, Holland C.; Ciardullo, Robin

1988-01-01

Nova shells are characteristically prolate with equatorial bands and polar caps. Failure to account for the geometry can lead to large errors in expansion parallaxes for individual novae. When simple prescriptions are used for deriving expansion parallaxes from an ensemble of randomly oriented prolate spheroids, the average distance will be too small by factors of 10 to 15 percent. The absolute magnitudes of the novae will be underestimated and the resulting distance scale will be too small by the same factors. If observations of partially resolved nova shells select for large inclinations, the systematic error in the resulting distance scale could easily be 20 to 30 percent. Extinction by dust in the bulge of M31 may broaden and shift the intrinsic distribution of maximum nova magnitudes versus decay rates. We investigated this possibility by projecting Arp's and Rosino's novae onto a composite B - 6200A color map of M31's bulge. Thirty two of the 86 novae projected onto a smooth background with no underlying structure due to the presence of a dust cloud along the line of sight. The distribution of maximum magnitudes versus fade rates for these unreddened novae is indistinguishable from the distribution for the entire set of novae. It is concluded that novae suffer very little extinction from the filamentary and patchy distribution of dust seen in the bulge of M31. Time average B and H alpha nova luminosity functions are potentially powerful new ways to use novae as standard candles. Modern CCD observations and the photographic light curves of M31 novae found during the last 60 years were analyzed to show that these functions are power laws. Consequently, unless the eruption times for novae are known, the data cannot be used to obtain distances.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitrani, J

Bayesian networks (BN) are an excellent tool for modeling uncertainties in systems with several interdependent variables. A BN is a directed acyclic graph, and consists of a structure, or the set of directional links between variables that depend on other variables, and conditional probabilities (CP) for each variable. In this project, we apply BN's to understand uncertainties in NIF ignition experiments. One can represent various physical properties of National Ignition Facility (NIF) capsule implosions as variables in a BN. A dataset containing simulations of NIF capsule implosions was provided. The dataset was generated from a radiation hydrodynamics code, and itmore » contained 120 simulations of 16 variables. Relevant knowledge about the physics of NIF capsule implosions and greedy search algorithms were used to search for hypothetical structures for a BN. Our preliminary results found 6 links between variables in the dataset. However, we thought there should have been more links between the dataset variables based on the physics of NIF capsule implosions. Important reasons for the paucity of links are the relatively small size of the dataset, and the sampling of the values for dataset variables. Another factor that might have caused the paucity of links is the fact that in the dataset, 20% of the simulations represented successful fusion, and 80% didn't, (simulations of unsuccessful fusion are useful for measuring certain diagnostics) which skewed the distributions of several variables, and possibly reduced the number of links. Nevertheless, by illustrating the interdependencies and conditional probabilities of several parameters and diagnostics, an accurate and complete BN built from an appropriate simulation set would provide uncertainty quantification for NIF capsule implosions.« less

ARCADE IMPLOSION CAUSED BY A FILAMENT ERUPTION IN A FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Juntao; Simões, P. J. A.; Fletcher, L.

Coronal implosions—the convergence motion of plasmas and entrained magnetic field in the corona due to a reduction in magnetic pressure—can help to locate and track sites of magnetic energy release or redistribution during solar flares and eruptions. We report here on the analysis of a well-observed implosion in the form of an arcade contraction associated with a filament eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events including the magnetic flux-rope instability and distortion, followed by a filament eruption and arcade implosion, lead us to conclude that the implosion arises from the transfer of magnetic energy from beneath the arcademore » as part of the global magnetic instability, rather than due to local magnetic energy dissipation in the flare. The observed net contraction of the imploding loops, which is found also in nonlinear force-free field extrapolations, reflects a permanent reduction of magnetic energy underneath the arcade. This event shows that, in addition to resulting in the expansion or eruption of an overlying field, flux-rope instability can also simultaneously implode an unopened field due to magnetic energy transfer. It demonstrates the “partial opening of the field” scenario, which is one of the ways in 3D to produce a magnetic eruption without violating the Aly–Sturrock hypothesis. In the framework of this observation, we also propose a unification of three main concepts for active region magnetic evolution, namely the metastable eruption model, the implosion conjecture, and the standard “CSHKP” flare model.« less

Magnetic Field Disturbances Associated with changes in Lithologic Stress

NASA Astrophysics Data System (ADS)

Johnston, J. M.; Budker, D.; Johnson, R. M.; Tchernychev, M.; Craig, M. S.

2013-12-01

In August 2013 demolition by implosion of a multistory building on the campus of California State University East Bay (CSUEB) provided a strong seismic wave source. Anticipating that this event might provide an opportunity to acquire measurements of magnetic phenomena that could be associated with temporal changes in the lithologic stress regime, we placed several total-field magnetometers in the vicinity of CSUEB. The proximity of the implosion site to the active trace of the Hayward Fault provided additional incentive to measure any magnetic response to the propagation of seismic waves. The instruments used at the implosion site included three total-field cesium vapor magnetometers. These were distributed so as to acquire measurements within 200 m of the implosion site and to straddle the Hayward fault. This experiment also used the total magnetic field measurements acquired at the Jasper Ridge Biological Preserve (JRBP) cesium vapor magnetometer in the foothills behind Stanford University, some 20 km from the implosion site, as a distant reference. All magnetometers were configured to sample at a rate of 10 Hz and were synchronized to better that 1 mSec relative to GPS time. The Magnetic field measurements were coordinated with seismic motion measurements recorded at approximately 600 residential seismic stations and several multichannel seismographs located around the demolition site. Magnetic phenomena that may be associated with lithologic stress phenomena are compared to the seismic measurements in an effort to the observe correlations between lithologic stress and the generation of an anomalous magnetic field. The coherence of the magnetic and seismic events should provide insight into the character of possible earthquake precursor magnetic signals.

A hybrid-drive nonisobaric-ignition scheme for inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, X. T., E-mail: xthe@iapcm.ac.cn; Center for Applied Physics and Technology, HEDPS, Peking University, Beijing 100871; IFSA Collaborative Innovation Center of MoE, Shanghai Jiao-Tong University, Shanghai 200240

A new hybrid-drive (HD) nonisobaric ignition scheme of inertial confinement fusion (ICF) is proposed, in which a HD pressure to drive implosion dynamics increases via increasing density rather than temperature in the conventional indirect drive (ID) and direct drive (DD) approaches. In this HD (combination of ID and DD) scheme, an assembled target of a spherical hohlraum and a layered deuterium-tritium capsule inside is used. The ID lasers first drive the shock to perform a spherical symmetry implosion and produce a large-scale corona plasma. Then, the DD lasers, whose critical surface in ID corona plasma is far from the radiationmore » ablation front, drive a supersonic electron thermal wave, which slows down to a high-pressure electron compression wave, like a snowplow, piling up the corona plasma into high density and forming a HD pressurized plateau with a large width. The HD pressure is several times the conventional ID and DD ablation pressure and launches an enhanced precursor shock and a continuous compression wave, which give rise to the HD capsule implosion dynamics in a large implosion velocity. The hydrodynamic instabilities at imploding capsule interfaces are suppressed, and the continuous HD compression wave provides main pdV work large enough to hotspot, resulting in the HD nonisobaric ignition. The ignition condition and target design based on this scheme are given theoretically and by numerical simulations. It shows that the novel scheme can significantly suppress implosion asymmetry and hydrodynamic instabilities of current isobaric hotspot ignition design, and a high-gain ICF is promising.« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikovich, A. L.; Schmit, P. F.

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikovich, A. L.; Schmit, P. F.

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

DOE PAGES

Velikovich, A. L.; Schmit, P. F.

2015-12-28

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Schmit, P. F.

2015-12-01

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining the "instantaneous growth rate" are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].

X-ray Heating and Electron Temperature of Laboratory Photoionized Plasmas

NASA Astrophysics Data System (ADS)

Mancini, Roberto; Lockard, Tom; Mayes, Daniel C.; Loisel, Guillaume; Bailey, James E.; Rochau, Gregory; Abdallah, J.; Golovkin, I.

2018-06-01

In separate experiments performed at the Z facility of Sandia National Laboratories two different samples were employed to produce and characterize photoionized plasmas. One was a gas cell filled with neon, and the other was a thin silicon layer coated with plastic. Both samples were driven by the broadband x-ray flux produced at the collapse of a wire array z-pinch implosion. Transmission spectroscopy of a narrowband portion of the x-ray flux was used to diagnose the charge state distribution, and the electron temperature was extracted from a Li-like ion level population ratio. To interpret the temperature measurement, we performed Boltzmann kinetics and radiation-hydrodynamic simulations. We found that non-equilibrium atomic physics and the coupling of the radiation flux to the atomic level population kinetics play a critical role in modeling the x-ray heating of photoionized plasmas. In spite of being driven by similar x-ray drives, differences of ionization and charged state distributions in the neon and silicon plasmas are reflected in the plasma heating and observed electron temperatures.This work was sponsored in part by DOE Office of Science Grant DE-SC0014451, and the Z Facility Fundamental Science Program of SNL.

Plasma Radiation Source Development Program

DTIC Science & Technology

2006-03-01

shell mass distributions perform belter than thin shells. The dual plenum, double shell load has unique diagnostic features that enhance our...as implosion time increases. 13. SUBJECT TERMS Zpinch x-ray diagnostics Rayleigh-Taylor instability pulsed-power x-ray spectroscopy supersonic...feature permits some very useful diagnostics that shed light on critical details of the implosion process. See Section 3 for details. We have

High-resolution Imaging of Deuterium-Tritium Capsule Implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Bachmann, Benjamin; Rygg, Ryan; Collins, Gilbert; Patel, Pravesh

2017-10-01

Highly-resolved 3-D simulations of inertial confinement fusion (ICF) implosions predict a hot spot plasma that exhibits complex micron-scale structure originating from a variety of 3-D perturbations. Experimental diagnosis of these conditions requires high spatial resolution imaging techniques. X-ray penumbral imaging can improve the spatial resolution over pinhole imaging while simultaneously increasing the detected photon yield at x-ray energies where the ablator opacity becomes negligible. Here we report on the first time-integrated x-ray penumbral imaging experiments of ICF capsule implosions at the National Ignition Facility that achieved spatial resolution as high as 4 micrometer. 6 to 30 keV hot spot images from layered DT implosions will be presented from a variety of experimental ICF campaigns, revealing previously unseen detail. It will be discussed how these and future results can be used to improve our physics understanding of inertially confined fusion plasmas by enabling spatially resolved measurements of hot spot properties, such as radiation energy, temperature or derived quantities. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

Hot spot mix in ICF implosions on the NIF

NASA Astrophysics Data System (ADS)

Ma, Tammy

2016-10-01

In the quest to achieve ignition through the inertial confinement fusion scheme, one of the critical challenges is to drive a symmetric implosion at high velocity without hydrodynamic instabilities becoming detrimental. These instabilities, primarily at the ablation front and the fuel-ablator interface, can cause mix of the higher-Z shell into the hot spot, resulting in increased radiation loss and thus reduced temperature and neutron yield. To quantify the level of mix, we developed a model that infers the level of hot spot contamination using the ratio of the enhanced x-ray production relative to the neutron yield. Applying this methodology to the full ensemble of indirect-drive National Ignition Facility (NIF) cryogenically layered DT implosions provides insight on the sensitivity of performance to the level of ablator-hot spot mix. In particular, the improvement seen with the High Foot design can be primarily attributed to a reduction in ablation-front instability mix that enabled the implosions to be pushed to higher velocity and performance. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, Lawrence Livermore National Security, LLC.

Analysis of staged Z-pinch implosion trajectories from experiments on Zebra

NASA Astrophysics Data System (ADS)

Ross, Mike P.; Conti, F.; Darling, T. W.; Ruskov, E.; Valenzuela, J.; Wessel, F. J.; Beg, F.; Narkis, J.; Rahman, H. U.

2017-10-01

The Staged Z-pinch plasma confinement concept relies on compressing an annular liner of high-Z plasma onto a target plasma column of deuterium fuel. The interface between the liner and target is stable against the Magneto-Rayleigh-Taylor Instability, which leads to effective fuel compression and makes the concept interesting as a potential fusion reactor. The liner initiates as a neutral gas puff, while the target plasma is a partially ionized (Zeff < 10 percent column ejected from a coaxial plasma gun. The Zebra pulsed power generator (1 MA peak current, 100 ns rise time) provides the discharge that ionizes the liner and drives the Z-pinch implosion. Diverse diagnostics observe the 100-300 km/s implosions including silicon diodes, photo-conducting detectors (PCDs), laser shadowgraphy, an XUV framing camera, and a visible streak camera. The imaging diagnostics track instabilities smaller than 0.1 mm, and Z-pinch diameters below 2.5 mm are seen at peak compression. This poster correlates the data from these diagnostics to elucidate implosion behavior dependencies on liner gas, liner pressure, target pressure, and applied, axial-magnetic field. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

Study of the formation, stability, and X-ray emission of the Z-pinch formed during implosion of fiber arrays at the Angara-5-1 facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V.; Volkov, G. S.; Grabovski, E. V.

Results from experimental studies on the implosion of arrays made of kapron fibers coated with different metals (Al, In, Sn, and Bi) are presented. It is shown that the power, total energy, and spectrum of radiation emitted by the imploding array depend on the number of metallized fibers and the mass of the metal layer deposited on them but are independent of the metal characteristics (density, atomic number, etc.). Analysis of frame X-ray images shows that the Z-pinches formed in the implosion of metallized kapron fiber arrays are more stable than those formed in wire arrays and that MHD perturbationsmore » in them develop at a slower growth rate. Due to the lower rate of plasma production from kapron fibers, the plasma formed at the periphery of the array forms a layer that plays the role of a hohlraum wall partially trapping soft X-ray emission of the Z-pinch formed in the implosion of the material of the deposited metal layer. The closure of the anode aperture doubles the energy of radiation emitted in the radial direction.« less

Neutron temporal diagnostic for high-yield deuterium-tritium cryogenic implosions on OMEGA

DOE PAGES

Stoeckl, C.; Boni, R.; Ehrne, F.; ...

2016-05-10

A next-generation neutron temporal diagnostic (NTD) capable of recording high-quality data for the highest anticipated yield cryogenic DT implosion experiments was recently installed at the Omega Laser Facility. A high-quality measurement of the neutron production width is required to determine the hot-spot pressure achieved in inertial confinement fusion experiments—a key metric in assessing the quality of these implosions. The design of this NTD is based on a fast-rise-time plastic scintillator, which converts the neutron kinetic energy to 350- to 450-nm-wavelength light. The light from the scintillator inside the nose-cone assembly is relayed ~16 m to a streak camera in amore » well-shielded location. An ~200× reduction in neutron background was observed during the first high-yield DT cryogenic implosions compared to the current NTD installation on OMEGA. An impulse response of ~40±10 ps was measured in a dedicated experiment using hard x rays from a planar target irradiated with a 10-ps short pulse from the OMEGA EP laser. Furthermore, the measured instrument response includes contributions from the scintillator rise time, optical relay, and streak camera.« less

Energy balance during underwater implosion of ductile metallic cylinders.

PubMed

Chamberlin, Ryan E; Guzas, Emily L; Ambrico, Joseph M

2014-11-01

Energy-based metrics are developed and applied to a numerical test case of implosion of an underwater pressure vessel. The energy metrics provide estimates of the initial energy in the system (potential energy), the energy released into the fluid as a pressure pulse, the energy absorbed by the imploding structure, and the energy absorbed by air trapped within the imploding structure. The primary test case considered is the implosion of an aluminum cylinder [diameter: 2.54 cm (1 in.), length: 27.46 cm (10.81 in.)] that collapses flat in a mode-2 shape with minimal fracture. The test case indicates that the structure absorbs the majority (92%) of the initial energy in the system. Consequently, the energy emitted as a pressure pulse into the fluid is a small fraction, approximately 5%, of the initial energy. The energy absorbed by the structure and the energy emitted into the fluid are calculated for additional simulations of underwater pressure vessel implosions. For all cases investigated, there is minimal fracture in the collapse, the structure absorbs more than 80% of the initial energy of the system, and the released pressure pulse carries away less than 6% of the initial energy.

Shock timing measurements and analysis in deuterium-tritium-ice layered capsule implosions on NIF

NASA Astrophysics Data System (ADS)

Robey, H. F.; Celliers, P. M.; Moody, J. D.; Sater, J.; Parham, T.; Kozioziemski, B.; Dylla-Spears, R.; Ross, J. S.; LePape, S.; Ralph, J. E.; Hohenberger, M.; Dewald, E. L.; Berzak Hopkins, L.; Kroll, J. J.; Yoxall, B. E.; Hamza, A. V.; Boehly, T. R.; Nikroo, A.; Landen, O. L.; Edwards, M. J.

2014-02-01

Recent advances in shock timing experiments and analysis techniques now enable shock measurements to be performed in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility (NIF). Previous measurements of shock timing in inertial confinement fusion implosions [Boehly et al., Phys. Rev. Lett. 106, 195005 (2011); Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] were performed in surrogate targets, where the solid DT ice shell and central DT gas were replaced with a continuous liquid deuterium (D2) fill. These previous experiments pose two surrogacy issues: a material surrogacy due to the difference of species (D2 vs. DT) and densities of the materials used and a geometric surrogacy due to presence of an additional interface (ice/gas) previously absent in the liquid-filled targets. This report presents experimental data and a new analysis method for validating the assumptions underlying this surrogate technique. Comparison of the data with simulation shows good agreement for the timing of the first three shocks, but reveals a considerable discrepancy in the timing of the 4th shock in DT ice layered implosions. Electron preheat is examined as a potential cause of the observed discrepancy in the 4th shock timing.

Neutron temporal diagnostic for high-yield deuterium–tritium cryogenic implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoeckl, C.; Boni, R.; Ehrne, F.

A next-generation neutron temporal diagnostic (NTD) capable of recording high-quality data for the highest anticipated yield cryogenic deuterium–tritium (DT) implosion experiments was recently installed at the Omega Laser Facility. A high-quality measurement of the neutron production width is required to determine the hot-spot pressure achieved in inertial confinement fusion experiments—a key metric in assessing the quality of these implosions. The design of this NTD is based on a fast-rise-time plastic scintillator, which converts the neutron kinetic energy to 350- to 450-nm-wavelength light. The light from the scintillator inside the nose-cone assembly is relayed ∼16 m to a streak camera inmore » a well-shielded location. An ∼200× reduction in neutron background was observed during the first high-yield DT cryogenic implosions compared to the current NTD installation on OMEGA. An impulse response of ∼40 ± 10 ps was measured in a dedicated experiment using hard x-rays from a planar target irradiated with a 10-ps short pulse from the OMEGA EP laser. The measured instrument response includes contributions from the scintillator rise time, optical relay, and streak camera.« less

Neutron temporal diagnostic for high-yield deuterium-tritium cryogenic implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoeckl, C.; Boni, R.; Ehrne, F.

A next-generation neutron temporal diagnostic (NTD) capable of recording high-quality data for the highest anticipated yield cryogenic DT implosion experiments was recently installed at the Omega Laser Facility. A high-quality measurement of the neutron production width is required to determine the hot-spot pressure achieved in inertial confinement fusion experiments—a key metric in assessing the quality of these implosions. The design of this NTD is based on a fast-rise-time plastic scintillator, which converts the neutron kinetic energy to 350- to 450-nm-wavelength light. The light from the scintillator inside the nose-cone assembly is relayed ~16 m to a streak camera in amore » well-shielded location. An ~200× reduction in neutron background was observed during the first high-yield DT cryogenic implosions compared to the current NTD installation on OMEGA. An impulse response of ~40±10 ps was measured in a dedicated experiment using hard x rays from a planar target irradiated with a 10-ps short pulse from the OMEGA EP laser. Furthermore, the measured instrument response includes contributions from the scintillator rise time, optical relay, and streak camera.« less

Simulating Coronal Loop Implosion and Compressible Wave Modes in a Flare Hit Active Region

NASA Astrophysics Data System (ADS)

Sarkar, Aveek; Vaidya, Bhargav; Hazra, Soumitra; Bhattacharyya, Jishnu

2017-12-01

There is considerable observational evidence of implosion of magnetic loop systems inside solar coronal active regions following high-energy events like solar flares. In this work, we propose that such collapse can be modeled in three dimensions quite accurately within the framework of ideal magnetohydrodynamics. We furthermore argue that the dynamics of loop implosion is only sensitive to the transmitted disturbance of one or more of the system variables, e.g., velocity generated at the event site. This indicates that to understand loop implosion, it is sensible to leave the event site out of the simulated active region. Toward our goal, a velocity pulse is introduced to model the transmitted disturbance generated at the event site. Magnetic field lines inside our simulated active region are traced in real time, and it is demonstrated that the subsequent dynamics of the simulated loops closely resemble observed imploding loops. Our work highlights the role of plasma β in regards to the rigidity of the loop systems and how that might affect the imploding loops’ dynamics. Compressible magnetohydrodynamic modes such as kink and sausage are also shown to be generated during such processes, in accordance with observations.

Multiple Experimental Platform Consistency at NIF

NASA Astrophysics Data System (ADS)

Benedetti, L. R.; Barrios, M. A.; Bradley, D. K.; Eder, D. C.; Khan, S. F.; Izumi, N.; Jones, O. S.; Ma, T.; Nagel, S. R.; Peterson, J. L.; Rygg, J. R.; Spears, B. K.; Town, R. P.

2013-10-01

ICF experiments at NIF utilize several platforms to assess different metrics of implosion quality. In addition to the point design-a target capsule of DT ice inside a thin plastic ablator-notable platforms include: (i) Symmetry Capsules(SymCaps), mass-adjusted CH capsules filled with DT gas for similar hydrodynamic performance without the need for a DT crystal; (ii) D:3He filled SymCaps, designed for low neutron yield implosions to accommodate a variety of x-ray and optical diagnostics; and (iii) Convergent Ablators, SymCaps coupled with x-radiography to assess in-flight velocity and symmetry of the implosion over ~1 ns before stagnation and burn. These platforms are expected to be good surrogates for one another, and their hohlraum and implosion performance variations have been simulated in detail. By comparing results of similar experiments, we isolate platform-specific variations. We focus on the symmetry, convergence, and timing of x-ray emission as observed in each platform as this can be used to infer stagnation pressure and temperature. This work performed under the auspices of the U.S. Dept. of Energy by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-640865.

Radiation characteristics and implosion dynamics of tungsten wire array Z-pinches on the YANG accelerator

NASA Astrophysics Data System (ADS)

Huang, Xian-Bin; Yang, Li-Bing; Li, Jing; Zhou, Shao-Tong; Ren, Xiao-Dong; Zhang, Si-Qun; Dan, Jia-Kun; Cai, Hong-Chun; Duan, Shu-Chao; Chen, Guang-Hua; Zhang, Zheng-Wei; Ouyang, Kai; Li, Jun; Zhang, Zhao-Hui; Zhou, Rong-Guo; Wang, Gui-Lin

2012-05-01

We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ~ 90 ns. The arrays are made up of (8-32) × 5 μm wires 6/10 mm in diameter and 15 mm in height. The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ~ 13 kJ and the energy conversion efficiency ~ 9% (24 × 5 μm wires, 6 mm in diameter). Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV, peaked at 250 and 375 eV. The dominant wavelengths of the wire ablation and the magneto-Rayleigh—Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images. Through analyzing the implosion trajectories obtained by an optical streak camera, the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about (1.3-2.1) × 107 cm/s.

Mix Model Comparison of Low Feed-Through Implosions

NASA Astrophysics Data System (ADS)

Pino, Jesse; MacLaren, S.; Greenough, J.; Casey, D.; Dewald, E.; Dittrich, T.; Khan, S.; Ma, T.; Sacks, R.; Salmonson, J.; Smalyuk, V.; Tipton, R.; Kyrala, G.

2016-10-01

The CD Mix campaign previously demonstrated the use of nuclear diagnostics to study the mix of separated reactants in plastic capsule implosions at the NIF. Recently, the separated reactants technique has been applied to the Two Shock (TS) implosion platform, which is designed to minimize this feed-through and isolate local mix at the gas-ablator interface and produce core yields in good agreement with 1D clean simulations. The effects of both inner surface roughness and convergence ratio have been probed. The TT, DT, and DD neutron signals respectively give information about core gas performance, gas-shell atomic mix, and heating of the shell. In this talk, we describe efforts to model these implosions using high-resolution 2D ARES simulations. Various methods of interfacial mix will be considered, including the Reynolds-Averaged Navier Stokes (RANS) KL method as well as and a multicomponent enhanced diffusivity model with species, thermal, and pressure gradient terms. We also give predictions of a upcoming campaign to investigate Mid-Z mixing by adding a Ge dopant to the CD layer. LLNL-ABS-697251 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Classical novae and recurrent novae: General properties

NASA Technical Reports Server (NTRS)

Hack, Margherita; Selvelli, Pierluigi; Duerbeck, Hilmar W.

1993-01-01

We describe the observable characteristics of classical novae and recurrent novae obtained by different techniques (photometry, spectroscopy, and imaging) in all the available spectral ranges. We consider the three stages in the life of a nova: quiescence (pre- and post-outburst), outburst, final decline and nebular phase. We describe the photometric properties during the quiescent phase. We describe the photometric properties during outburst, the classification according the rate of decline (magnitudes per day), which permits us to define very fast, fast, intermediate, slow, and very slow novae and the correlation between luminosity and speed class. We report the scanty data on the spectra of the few known prenovae and those on the spectra of old novae and those of dwarf novae and nova-like, which, however, are almost undistinguishable. We describe the typical spectra appearing from the beginning of the outburst, just before maximum, up to the nebular phase and the correlation between spectral type at maximum, expansional velocity, and speed class of the nova. We report the existing infrared observations, which permit us to explain some of the characteristics of the outburst light curve, and give evidence of the formation of a dust shell in slow and intermediate novae (with the important exception of the very slow nova HR Del 1967) and its absence or quasi-absence in fast novae. The ultraviolet and X-ray observations are described. The X ray observations of novae, mainly from the two satellites EINSTEIN and EXOSAT, are reported. Observations of the final decline and of the envelopes appearing several months after outburst are also reported.

Inertial confinement fusion ablator physics experiments on Saturn and Nova

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, R.E.; Porter, J.L.; Chandler, G.A.

1997-05-01

The Saturn pulsed power accelerator [R. B. Spielman {ital et al.}, in {ital Proceedings of the 2nd International Conference on Dense} Z-{ital pinches}, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] at Sandia National Laboratories (SNL) and the Nova laser [J. T. Hunt and D. R. Speck, Opt. Eng. {bold 28}, 461 (1989)] at Lawrence Livermore National Laboratory (LLNL) have been used to explore techniques for studying the behavior of ablator material in x-ray radiation environments comparable in magnitude, spectrum, and duration to those thatmore » would be experienced in National Ignition Facility (NIF) hohlraums [J. D. Lindl, Phys. Plasmas {bold 2}, 3933 (1995)]. The large x-ray outputs available from the Saturn pulsed-power-driven z pinch have enabled us to drive hohlraums of full NIF ignition scale size at radiation temperatures and time scales comparable to those required for the low-power foot pulse of an ignition capsule. The high-intensity drives available in the Nova laser have allowed us to study capsule ablator physics in smaller-scale hohlraums at radiation temperatures and time scales relevant to the peak power pulse for an ignition capsule. Taken together, these experiments have pointed the way to possible techniques for testing radiation-hydrodynamics code predictions of radiation flow, opacity, equation of state, and ablator shock velocity over the range of radiation environments that will be encountered in a NIF hohlraum. {copyright} {ital 1997 American Institute of Physics.}« less

The classical nova hibernation scenario: a definitive confirmation

NASA Astrophysics Data System (ADS)

Gaensicke, Boris

2017-08-01

The detached white dwarf plus M-dwarf binary LL Eri exhibits truly unique behaviour within this class of compact binaries. As part of a COS snapshot survey, we detected large-amplitude variability in the ultraviolet flux of the white dwarf, confirmed by extensive ground-based blue-band photometry. The three independent frequencies detected in the light curves clearly identify this variability as non-radial pulsations of the white dwarf. However, with a hydrogen atmosphere and Teff=17200K, this white dwarf is nearly 5000K hotter than the canonical instability strip.The COS spectrum, albeit noisy, reveals that the metal lines typically detected in this class of stars, arising from material captured from the M-dwarf wind, are very broad. If interpreted as rotationally broadened, they imply a spin of only a few minutes. Such a short period could be explained by a past phase of intense accretion of mass and angular momentum. It has been postulated for over thirty years that classical nova eruptions on the white dwarf could cause such switching from a semi-detached to a detached binary configuration, during which the system hibernates - yet, to date no hibernating nova has been identified. However, the broad lines could also be due to pulsation-driven surface velocity fields, in which case the nature and past evolution of LL Eri would not be easily linked to any exisiting scenario for compact binary evolution. We propose to obtain a deeper COS observations to unambiguosly determine whether the cause of the observed line broadening is due to rapid rotation, which would unequivocally confirm the hibernation scenario.

Time-of-Flight Measurements of Neutron Yields from Implosions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Caggaino, Joseph

2014-10-01

Three 20-m time-of-flight detectors measure neutron spectra from implosions of deuterium-tritium targets at the National Ignition Facility. Two prominent peaks appear in the spectra from the T(d, n) and D(d, n) reactions. The ratio of yields extracted from the peaks depend on the DT and DD reaction rates and attenuation from the compressed DT fuel, which makes the ratio a diagnostic of the hotspot thermodynamics and fuel areal density. The measured peak widths provide additional constraints on reactant temperature. Recent measurements from a high-yield campaign will be presented and compared to radiation-hydrodynamic simulations of similar implosions. This research is supported by the Department of Energy National Nuclear Security Administration under Contract DE-NA0001944.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

DOE PAGES

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; ...

2018-02-22

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. Direct-drive implosions at the National Ignition Facility were conducted to reduce CBET by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams over the equatorial region of the target. For the first time, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in themore » average ablation pressure.« less

A comparison of hydro-instabilities in CH, HDC, and beryllium ablators on NIF

NASA Astrophysics Data System (ADS)

Smalyuk, V. A.; Robey, H. F.; Ali, S.; Berzak Hopkins, L. F.; Casey, D. T.; Celliers, P. M.; Clark, D. S.; Felker, S. J.; Field, J. E.; Haan, S. W.; Hammel, B. A.; Hsing, W. W.; Kroll, J. J.; Landen, O. L.; Lepape, S.; Macphee, A. G.; Martinez, D.; Milovich, J.; Nikroo, A.; Pickworth, L.; Stadermann, M.; Weber, C. R.; Kline, J.; Loomis, E.; Yi, A.

2017-10-01

A comparison of the hydrodynamic growth in plastic, high-density carbon, and beryllium ablators will be presented in indirect-drive implosions on National Ignition Facility. This comparison is based on experimentally measured instabilities in all phases of implosions for the three ablators. The 2-D and 3-D perturbations were measured at the ablation-surface with the Hydrodynamic Growth Radiography platform. In the deceleration phase of implosions, innovative self-emission and ``self-backlight'' techniques were used. Results of the 3-D perturbation growth including engineering features will also be presented for convergence up to 20 and compared for the three ablators. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.

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. Direct-drive implosions at the National Ignition Facility were conducted to reduce CBET by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams over the equatorial region of the target. For the first time, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in themore » average ablation pressure.« less

Implosion spectroscopy in Rugby hohlraums on OMEGA

NASA Astrophysics Data System (ADS)

Philippe, Franck; Tassin, Veronique; Bitaud, Laurent; Seytor, Patricia; Reverdin, Charles

2014-10-01

The rugby hohlraum concept has been validated in previous experiments on the OMEGA laser facility. This new hohlraum type can now be used as a well-characterized experimental platform to study indirect drive implosion, at higher radiation temperatures than would be feasible at this scale with classical cylindrical hohlraums. Recent experiments have focused on the late stages of implosion and hotspot behavior. The capsules included both a thin buried Titanium tracer layer, 0-3 microns from the inner surface, Argon dopant in the deuterium gas fuel and Germanium doped CH shells, providing a variety of spectral signatures of the plasma conditions in different parts of the target. X-ray spectroscopy and imaging were used to study compression, Rayleigh-Taylor instabilities growth at the inner surface and mix between the shell and gas.

A statistical analysis of IUE spectra of dwarf novae and nova-like stars

NASA Technical Reports Server (NTRS)

Ladous, Constanze

1990-01-01

First results of a statistical analysis of the IUE International Ultraviolet Explorer archive on dwarf novae and nova like stars are presented. The archive contains approximately 2000 low resolution spectra of somewhat over 100 dwarf novae and nova like stars. Many of these were looked at individually, but so far the collective information content of this set of data has not been explored. The first results of work are reported.

Gamma Rays from Classical Novae

NASA Technical Reports Server (NTRS)

1997-01-01

NASA at the University of Chicago, provided support for a program of theoretical research into the nature of the thermonuclear outbursts of the classical novae and their implications for gamma ray astronomy. In particular, problems which have been addressed include the role of convection in the earliest stages of nova runaway, the influence of opacity on the characteristics of novae, and the nucleosynthesis expected to accompany nova outbursts on massive Oxygen-Neon-Magnesium (ONeMg) white dwarfs. In the following report, I will identify several critical projects on which considerable progress has been achieved and provide brief summaries of the results obtained:(1) two dimensional simulation of nova runaway; (2) nucleosynthesis of nova modeling; and (3) a quasi-analytic study of nucleosynthesis in ONeMg novae.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hachisu, Izumi; Kato, Mariko, E-mail: hachisu@ea.c.u-tokyo.ac.jp, E-mail: mariko@educ.cc.keio.ac.jp

We identified a general course of classical nova outbursts in the B – V versus U – B color-color diagram. It is reported that novae show spectra similar to those of A-F supergiants near optical light maximum. However, they do not follow the supergiant sequence in the color-color diagram, neither the blackbody nor the main-sequence sequence. Instead, we found that novae evolve along a new sequence in the pre-maximum and near-maximum phases, which we call 'the nova-giant sequence'. This sequence is parallel to but Δ(U – B) ≈ –0.2 mag bluer than the supergiant sequence. This is because the massmore » of a nova envelope is much (∼10{sup –4} times) less than that of a normal supergiant. After optical maximum, its color quickly evolves back blueward along the same nova-giant sequence and reaches the point of free-free emission (B – V = –0.03, U – B = –0.97), which coincides with the intersection of the blackbody sequence and the nova-giant sequence, and remains there for a while. Then the color evolves leftward (blueward in B – V but almost constant in U – B), owing mainly to the development of strong emission lines. This is the general course of nova outbursts in the color-color diagram, which was deduced from eight well-observed novae in various speed classes. For a nova with unknown extinction, we can determine a reliable value of the color excess by matching the observed track of the target nova with this general course. This is a new and convenient method for obtaining the color excesses of classical novae. Using this method, we redetermined the color excesses of 20 well-observed novae. The obtained color excesses are in reasonable agreement with the previous results, which in turn support the idea of our general track of nova outbursts. Additionally, we estimated the absolute V magnitudes of about 30 novae using a method for time-stretching nova light curves to analyze the distance-reddening relations of the novae.« less

The spectroscopic evolution of novae in the bulge of M31 and a search for their possible origin in the M31 globular cluster system

NASA Astrophysics Data System (ADS)

Tomaney, Austin Bede

Results are presented from a three year (1987 to 1989) spectroscopic and photometric survey of novae in M3l's bulge, the first comprehensive study of novae outside the Galactic and Magellanic Cloud systems. Nine novae were detected and monitored and their spectra cover a range of outburst states from early decline to the early nebular phases. Broad agreement in spectral morphology and evolution is found with Galactic novae. Since Galactic novae are mainly disk objects, this indicates that novae outburst properties are not critically dependent on the metallicity of the progenitor population. However, in this sample, and in a sample of four M31 nova spectra taken in 1983, no fast, violent outbursts frequently associated with nova systems containing ONeMg white dwarfs were found, suggestive of a systematic difference between the observed proportion of such outbursts between Galactic and M31 bulge novae. Three novae in the sample were observed on succeeding nights during the transition phase of their evolution. Extraordinary variations in some nightly line strengths, particularly the N III lines, were discovered. It is argued that this variability reflects the deposition of drag energy by the secondary star during the common envelope phase of nova evolution and is indicative of a key phase in mass loss from nova systems. Observations include the spectroscopic coverage of an extremely slow nova from 1987 to l990, during the object's evolution in the nebula phase. This provided a unique opportunity to make the first detailed comparison of the evolution and properties of an extra galactic nova with those in our own Galaxy. The roughly solar abundances obtained are typical of similar slow Galactic novae. Further observations are also presented of a unique outburst in 1988 that was independently discovered and reported by Rich et al. These data confirm the inferences of other observers that the outburst differed markedly from that of a typical classical nova. Finally an extensive spectroscopic survey of the M31 globular cluster system was made in an effort to find evidence of a previously suggested enhanced nova rate in these objects. No outbursts were detected during an effective survey time of one year for the entire system.

Search for gamma-ray emission from Galactic novae with the Fermi -LAT

NASA Astrophysics Data System (ADS)

Franckowiak, A.; Jean, P.; Wood, M.; Cheung, C. C.; Buson, S.

2018-02-01

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims: We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods: We repeated the analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results: Two new novae candidates have been found at 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.

Search for gamma-ray emission from Galactic novae with the Fermi-LAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franckowiak, A.; Jean, P.; Wood, M.

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims. We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods. We repeated themore » analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results. Two new novae candidates have been found at ~ 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Lastly, our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.« less

Search for gamma-ray emission from Galactic novae with the Fermi-LAT

DOE PAGES

Franckowiak, A.; Jean, P.; Wood, M.; ...

2018-02-05

Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically detected Galactic novae in the first 7.4 years of operation of the Fermi Large Area Telescope using the Pass 8 data set. Aims. We compile an optical nova catalog including light curves from various resources and estimate the optical peak time and optical peak magnitude in order to search for gamma-ray emission to determine whether all novae are gamma-ray emitters. Methods. We repeated themore » analysis of the six novae previously identified as gamma-ray sources and developed a unified analysis strategy that we then applied to all novae in our catalog. We searched for emission in a 15 day time window in two-day steps ranging from 20 days before to 20 days after the optical peak time. We performed a population study with Monte Carlo simulations to set constraints on the properties of the gamma-ray emission of novae. Results. Two new novae candidates have been found at ~ 2σ global significance. Although these two novae candidates were not detected at a significant level individually, taking them together with the other non-detected novae, we found a sub-threshold nova population with a cumulative 3σ significance. We report the measured gamma-ray flux for detected sources and flux upper limits for novae without significant detection. Lastly, our results can be reproduced by several gamma-ray emissivity models (e.g., a power-law distribution with a slope of 2), while a constant emissivity model (i.e., assuming novae are standard candles) can be rejected.« less

Recent progress in understanding the eruptions of classical novae

NASA Technical Reports Server (NTRS)

Shara, Michael M.

1988-01-01

Dramatic progress has occurred in the last two decades in understanding the physical processes and events leading up to, and transpiring during the eruption of a classical nova. The mechanism whereby a white dwarf accreting hydrogen-rich matter from a low-mass main-sequence companion produces a nova eruption has been understood since 1970. The mass-transferring binary stellar configuration leads inexorably to thermonuclear runaways detected at distances of megaparsecs. Summarized here are the efforts of many researchers in understanding the physical processes which generate nova eruptions; the effects upon nova eruptions of different binary-system parameters (e.g., chemical composition or mass of the white dwarf, different mass accretion rates); the possible metamorphosis from dwarf to classical novae and back again; and observational diagnostics of novae, including x ray and gamma ray emission, and the characteristics and distributions of novae in globular clusters and in extragalactic systems. While the thermonuclear-runaway model remains the successful cornerstone of nova simulation, it is now clear that a wide variety of physical processes, and three-dimensional hydrodynamic simulations, will be needed to explain the rich spectrum of behavior observed in erupting novae.

Nova V2214 Ophiuchi 1988 - A magnetic nova inside the period gap

NASA Technical Reports Server (NTRS)

Baptista, R.; Jablonski, F. J.; Cieslinski, D.; Steiner, J. E.

1993-01-01

The discovery of a coherent photometric modulation in Nova Oph 1988 with period 0.117515 +/- 0.000002 d, which is associated with the orbital period of the underlying binary, is reported. On the basis of photometric observations, it is concluded that Nova V2214 Oph 1988 is a magnetic nova with an orbital period inside the period gap. The inclusion of this system in the statistics of novae suggests that there is no period gap for novae and that there is a clear correlation between the occurrence of novae with short orbital periods and the presence of magnetic white dwarfs. It is suggested that funneling of the accretion flow onto the magnetic poles favors the conditions for a thermonuclear runaway, increasing the frequency of eruptions for magnetic systems.

LLE Review Quarterly Report January - March 2012. Volume 130

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvydky, Alex

2012-03-01

This volume of the LLE Review, covering January–March 2012, features “OMEGA Polar-Drive Target Designs,” by P. B. Radha, J. A. Marozas, F. J. Marshall, A. Shvydky, T. J. B. Collins, V. N. Goncharov, R. L. McCrory, P. W. McKenty, D. D. Meyerhofer, T. C. Sangster, and S. Skupsky. This article (p. 57) describes low-adiabat, cryogenic-deuterium–tritium, and warm-plastic-shell polar-drive (PD)–implosion designs for the OMEGA laser. The designs are at two different on-target laser intensities, each at a different in-flight aspect ratio (IFAR). The first design permits one to study implosion energetics and target performance closer to ignition-relevant intensities (7 X 10more » 14 W/cm 2 at the quarter-critical surface), where nonlocal heat conduction and laser–plasma interactions can play an important role, but at lower values of IFAR (~22). The second design permits one to study implosion energetics and target performance at a lower intensity (3 X 10 14 W/cm 2) but at higher IFAR (~32), where the shell instability can play an important role. The higher IFAR designs are accessible on the existing OMEGA Laser System only at lower intensities. Implosions at ignition-relevant intensities can be obtained only by reducing target radius, although only at smaller values of IFAR. Polar-drive geometry requires repointing the laser beams to improve shell symmetry. The higher-intensity designs optimize target performance by repointing beams to a lesser extent and compensate for the reduced equatorial drive by increasing beam energies for the repointed beams and using custom beam profiles that improve equatorial illumination at the expense of irradiation at higher latitudes. These designs will be studied when new phase plates for the OMEGA Laser System, corresponding to the smaller target radii and custom beam profiles, are obtained. Implosion results from the combined set of high-intensity and high-IFAR implosions should yield valuable data to validate models of laser-energy deposition, heat conduction, nonuniformity growth, and fuel assembly in PD geometry.« less

Incubation pit analysis and calculation of the hydrodynamic impact pressure from the implosion of an acoustic cavitation bubble.

PubMed

Tzanakis, I; Eskin, D G; Georgoulas, A; Fytanidis, D K

2014-03-01

An experimental study to evaluate cavitation bubble dynamics is conducted. The aim is to predict the magnitude and statistical distribution of hydrodynamic impact pressure generated from the implosion of various individual acoustic cavitation bubbles near to a rigid boundary, considering geometrical features of the pitted area. A steel sample was subjected to cavitation impacts by an ultrasonic transducer with a 5mm diameter probe. The pitted surface was then examined using high-precision 3D optical interferometer techniques. Only the incubation period where surface is plastically deformed without material loss is taken into account. The exposure time was adjusted in the range of 3-60 s to avoid pit overlapping and a special procedure for pit analysis and characterisation was then followed. Moreover, a high-speed camera device was deployed to capture the implosion mechanisms of cavitation bubbles near to the surface. The geometrical characteristics of single incubation pits as well as pit clusters were studied and their deformation patterns were compared. Consequently, a reverse engineering approach was applied in order the hydrodynamic impact pressure from the implosion of an individual cavitation bubble to be determined. The characteristic parameters of the cavitation implosion process such as hydrodynamic impact pressure and liquid micro-jet impact velocity as well as the hydrodynamic severity of the cavitation impacts were quantified. It was found that the length of the hypotenuse of the orthographic projections from the center of the pit, which basically represents the deformed area of the pit, increases with the hydrodynamic impact aggressiveness in a linear rate. Majority of the hydrodynamic impacts were in the range of 0.4-1 GPa while the corresponding micro-jet velocities were found to be in the range of 200-700 m/s. Outcomes of this study, contribute to further understanding the cavitation intensity from the implosion of acoustically generated bubbles and could certainly represent a significant step towards developing more accurate cavitation models. Copyright © 2013 Elsevier B.V. All rights reserved.

Approximate models for the ion-kinetic regime in inertial-confinement-fusion capsule implosions

DOE PAGES

Hoffman, Nelson M.; Zimmerman, George B.; Molvig, Kim; ...

2015-05-19

“Reduced” (i.e., simplified or approximate) ion-kinetic (RIK) models in radiation-hydrodynamic simulations permit a useful description of inertial-confinement-fusion (ICF) implosions where kinetic deviations from hydrodynamic behavior are important. For implosions in or near the kinetic regime (i.e., when ion mean free paths are comparable to the capsule size), simulations using a RIK model give a detailed picture of the time- and space-dependent structure of imploding capsules, allow an assessment of the relative importance of various kinetic processes during the implosion, enable explanations of past and current observations, and permit predictions of the results of future experiments. The RIK simulation method describedmore » here uses moment-based reduced kinetic models for transport of mass, momentum, and energy by long-mean-free-path ions, a model for the decrease of fusion reactivity owing to the associated modification of the ion distribution function, and a model of hydrodynamic turbulent mixing. Transport models are based on local gradient-diffusion approximations for the transport of moments of the ion distribution functions, with coefficients to impose flux limiting or account for transport modification. After calibration against a reference set of ICF implosions spanning the hydrodynamic-to-kinetic transition, the method has useful, quantifiable predictive ability over a broad range of capsule parameter space. Calibrated RIK simulations show that an important contributor to ion species separation in ICF capsule implosions is the preferential flux of longer-mean-free-path species out of the fuel and into the shell, leaving the fuel relatively enriched in species with shorter mean free paths. Also, the transport of ion thermal energy is enhanced in the kinetic regime, causing the fuel region to have a more uniform, lower ion temperature, extending over a larger volume, than implied by clean simulations. Furthermore, we expect that the success of our simple approach will motivate continued theoretical research into the development of first-principles-based, comprehensive, self-consistent, yet useable models of kinetic multispecies ion behavior in ICF plasmas.« less

A Hubble Space Telescope survey for Novae in M87. II. Snuffing out the maximum magnitude–rate of decline relation for novae as a non-standard candle, and a prediction of the existence of ultrafast novae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shara, Michael M.; Doyle, Trisha; Lauer, Tod R.

The extensive grid of numerical simulations of nova eruptions first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are inmore » the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10 –7–10 –8 M ⊙, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. As a result, these same models predict the existence of ultrafast novae that display decline times, t 2, to be as short as five hours. We outline a strategy for their future detection.« less

A Hubble Space Telescope Survey for Novae in M87. II. Snuffing out the Maximum Magnitude–Rate of Decline Relation for Novae as a Non-standard Candle, and a Prediction of the Existence of Ultrafast Novae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shara, Michael M.; Doyle, Trisha; Zurek, David

The extensive grid of numerical simulations of nova eruptions from the work of Yaron et al. first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giantmore » elliptical galaxy M87 as they are in the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10{sup −7}–10{sup −8} M {sub ⊙}, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. These same models predict the existence of ultrafast novae that display decline times, t {sub 2,} to be as short as five hours. We outline a strategy for their future detection.« less

A Hubble Space Telescope survey for Novae in M87. II. Snuffing out the maximum magnitude–rate of decline relation for novae as a non-standard candle, and a prediction of the existence of ultrafast novae

DOE PAGES

Shara, Michael M.; Doyle, Trisha; Lauer, Tod R.; ...

2017-04-20

The extensive grid of numerical simulations of nova eruptions first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are inmore » the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10 –7–10 –8 M ⊙, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. As a result, these same models predict the existence of ultrafast novae that display decline times, t 2, to be as short as five hours. We outline a strategy for their future detection.« less

First optical candidate for a recovered classical nova in a globular cluster - Nova 1938 in M14

NASA Technical Reports Server (NTRS)

Shara, Michael M.; Potter, Michael; Moffat, Anthony F. J.; Hogg, Helen S.; Wehlau, Amelia

1986-01-01

U, B, V, R, and H-alpha CCD frames of the field of the nova which appeared in the globular cluster M14 in 1938 have been compared with the nova discovery images. On the basis of positional coincidence, brightness, and blue color, a candidate nova was identified and its right ascension and declination to within 1 arcsec each. Confirmation of the candidate and detailed study of the quiescent nova will probably require Hubble Space Telescope observations.

Identification of Recurrent Novae in M31

NASA Astrophysics Data System (ADS)

Shafter, Allen W.; Rector, T. A.; Schweizer, F.; Bryan, J.

2014-01-01

Over roughly the past century a total of more than 900 optical transient events have been recorded in M31, the vast majority of which are believed to represent eruptions of classical novae. The impressive dataset of nova positions put together by Pietsch (http://www.mpe.mpg.de m31novae/opt/m31/) provides the opportunity to search for multiple nova outbursts from the same progenitor system, and thus to characterize the population of recurrent novae (RNe) in M31. In order to identify RNe candidates, we have searched for spatial near coincidences among the 945 recorded novae given in the Pietsch catalog through the end of August 2013. Given that the positions of many of the early novae are quite uncertain, we have set our initial screen to include nova pairs with nominal separations less than or equal to 6 arcsec. We have identified a total of 102 novae that pass this coarse screen. Of these, 78 novae form 39 pairs, 15 form five triples, four novae are part of a quad, and five novae form a quint. As demonstrated by Shafter, Rice and Daub (2009, presented at the "Wild Stars in the Old West II" conference, mintaka.sdsu.edu/faculty/shafter/extragalactic_novae/RNePoster4.pdf), the majority of the 102 novae surviving our initial screen are expected to be associated with chance positional near coincidences (especially near the nucleus), and are not RNe. To decide which candidates are indeed RNe, we have undertaken a study to locate the original discovery plates, CCD images or published finding charts, and to perform the necessary astrometry to identify which of our candidate RNe are chance positional coincidences, and which are RNe. For each candidate, we estimate the probability that the object is a chance positional coincidence as in Shafter et al. (2009). To date, we have been successful in identifying finding charts or original images for most of the candidates, and have found a total of 23 nova outbursts in M31 associated with 10 systems that are almost certainly RNe.

Infrared spectroscopy of the remnant of Nova Sco 2014: a symbiotic star with too little circumstellar matter to decelerate the ejecta

NASA Astrophysics Data System (ADS)

Munari, U.; Banerjee, D. P. K.

2018-03-01

Pre-outburst 2MASS and WISE photometry of Nova Sco 2014 (V1534 Sco) has suggested the presence of a cool giant at the location of the nova in the sky. The spectral evolution recorded for the nova did not, however, support a direct partnership because no flash-ionized wind and no deceleration of the ejecta were observed, contrary to the behaviour displayed by other novae which erupted within symbiotic binaries like V407 Cyg or RS Oph. We have therefore obtained 0.8-2.5 μm spectra of the remnant of Nova Sco 2014 in order to ascertain if a cool giant is indeed present and if it is physically associated with the nova. The spectrum shows the presence of a M6III giant, reddened by E(B - V) = 1.20, displaying the typical and narrow emission-line spectrum of a symbiotic star, including He I 1.0830 μm with a deep P-Cyg profile. This makes Nova Sco 2014 a new member of the exclusive club of novae that erupt within a symbiotic binary. Nova Sco 2014 shows that a nova erupting within a symbiotic binary does not always come with a deceleration of the ejecta, contrary to the common belief. Many other similar systems may lay hidden in past novae, especially in those that erupted prior to the release of the 2MASS all-sky infrared survey, which could be profitably cross-matched now against them.