Symmetry tuning and high energy coupling for an Al capsule in a Au rugby hohlraum on NIF

Ping, Yuan; Smalyuk, V. A.; Amendt, Peter; Khan, S. F.; Tommasini, R.; Dewald, E. L.; Field, J. E.; Graziani, Frank; Hartouni, E. P.; Johnson, S.; Landen, O. L.; Lindl, J. D.; MacPhee, A. G.; Nikroo, A.; Nora, R.; Prisbrey, Shon; Ralph, J. E.; Seugling, R M; Strozzi, D. J.; Tipton, Robert; Wang, Y. M.; Kim, Y.; Loomis, Eric; Meaney, K. D.; Merritt, Elizabeth; Montgomery, D. S.; Kabadi, N.; Lahmann, B.; Petrasso, R. D.

doi:10.1063/5.0021183

Cited by 5 publications

(7 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our previous work [7,8], a good agreement between measurements and simulations was reached for 3 mm-diameter aluminum capsules in a gold rugby hohlraum driven by a reverse-ramp pulse shape. In that case, the high-power laser pulse interacted directly with a clean gold wall since there was very little picket pulse.…”

Section: Improvements For Future Experimentsmentioning

confidence: 61%

“…The simulations used to design and model the experiment were fully integrated (hohlraum + capsule + gas fill + laser), 2D radiation-hydrodynamic simulations based on the LAS-NEX code [16], similar to our previous work [7,8]. There was no drive multiplier used and an electron thermal flux limiter of 0.04 was found to best match the measured bang time at the cost of too prolate an implosion; conversely, a flux limit of 0.07 better reproduced the observed core symmetry but at the cost of a nearly 800 ps early bang time.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

“…To investigate possible physical processes that could contribute to the symmetry discrepancy, we performed two additional 2D simulations by varying the glint percentage of the 50 • cone beams: one with glint turned off and the other with glint capped at 25% at a turning point for n/n c > 0.1, where n c is the critical density. The glint, or reflected laser light at the hohlraum wall, is responsible for symmetry tuning when the wall curvature is varied [8]. By artificially reducing the amount of the glint in the outermost cone (50 • ) in the simulation, more drive is concentrated at the pole than at the equator, leading to a more oblate hot spot.…”

Section: Symmetry and Leh Emissionmentioning

confidence: 99%

“…It has also been recognized that there are still many challenges on the path towards ignition [6], including low energy coupling efficiency, implosion asymmetries, hydrodynamic instabilities, and engineering features in the target, etc. Recently we reported enhanced energy coupling to aluminum capsules in a gold rugby hohlraum with a reverse-ramp laser drive [7,8]. The increase in the coupling efficiency from ∼10% to ∼30% was mainly a result of smaller case-to-capsule ratio, i.e.…”

Section: Introductionmentioning

confidence: 97%

“…The rugby hohlraum [9,10] has a surface area ∼30% smaller than a cylindrical hohlraum with the same diameter at the equator, which is beneficial to accommodate large capsules while minimizing surface losses. The symmetry of the aluminum shell was tuned by modifying the curvature of the rugby wall to achieve a round implosion at a relatively low convergence of ∼10x for a double-shell ignition design [8].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF

Ping¹,

Amendt²,

Baker³

et al. 2021

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

In the laser-driven indirect drive scheme for inertial confinement fusion, the energy coupling efficiency from the hohlraum to the capsule is typically ∼10% due to limited capsule sizes in order to attain quasi-round implosions with currently available laser energy in cylindrical hohlraums. Recent experiments at the National ignition Facility (NIF) showed ∼30% energy coupling efficiency to aluminum capsules by using a rugby-shaped hohlraum to accommodate larger capsules. This paper reports the first experiment at the NIF demonstrating ∼30% energy coupling to a 3 mm-diameter high-energy-density carbon capsule in a rugby hohlraum with a two-shock laser pulse shape. By comparing the measured bang time with a simulated hydrodynamic scaling, ∼430 kJ coupling is inferred with 1.36 MJ laser drive. The symmetry of the hot spot was observed to be more oblate than simulations predicted. X-ray images taken at late time show strong emission at the laser entrance hole of the rugby hohlraum, indicating a closure earlier than expected, which could contribute to the oblate hot spot shape. Implementing wavelength detuning or modifying the hohlraum shape to tune the symmetry in future experiments would allow symmetric implosions while maintaining the high energy coupling.

show abstract

Section: Improvements For Future Experimentsmentioning

confidence: 61%

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

Section: Symmetry and Leh Emissionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF

Ping¹,

Amendt²,

Baker³

et al. 2021

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

High-volume and -adiabat capsule (“HVAC”) ignition: Lowered fuel compression requirements using advanced Hohlraums

Amendt

Nora

et al. 2020

Physics of Plasmas

View full text Add to dashboard Cite

Lower-than-expected deuterium–tritium fuel areal densities have been experimentally inferred across a variety of high-convergence, nominally low-adiabat implosion campaigns at the National Ignition Facility (NIF) using cylinder-shaped Hohlraums [Hurricane et al., Phys. Plasmas 26, 052704 (2019)]. A leading candidate explanation is the presence of atomic mix between the fuel and ablator from hydrodynamic instability growth [Clark et al., Phys. Plasmas 26, 050601 (2019)], leading to reduced fuel compressibility and an effectively higher (in-flight) fuel adiabat α. Tolerating a high-α implosion can be obtained with significantly higher capsule absorbed energy Ecap according to the one-dimensional (1-D) ignition-threshold-factor analytic scaling [S. Atzeni and J. Meyer-ter-Vehn, Nucl. Fusion 41, 465 (2001)], ITF∼Ecap·α−1.8. Recent experiments with large Al shells in rugby-shaped Hohlraums have established high laser-capsule coupling efficiencies of ≽ 30% [Ping et al., Nat. Phys. 15, 138 (2019)], enabling a path to Ecap≽ 0.5 MJ at the NIF and increased performance margin M ≡ ITF − 1. The ability to operate at high adiabat with large capsules using nonstandard Hohlraums leads to the predicted onset of a volume-ignition mode, defined as when both the entire fuel is the “hot spot” and inertial confinement is principally provided by the ablator compared with the compressed fuel. Such an ignition mode, normally reserved for high-Z targets, e.g., double shells [Amendt et al., Phys. Plasmas 14, 056312 (2007)], is predicted to lead to lower fuel convergence and less exposure to mix due to the intended high adiabat—but at the expense of ∼3–4 × reduced (1-D) yield compared with conventional central hot-spot ignition designs.

show abstract

Detrimental effects and mitigation of the joint feature in double shell implosion simulations

et al. 2021

View full text Add to dashboard Cite

Double shell capsules provide an attractive option in inertial confinement fusion experiments due to their potential for achieving a low-convergence, robust burn. However, these designs suffer from symmetry degradation and accompanying reduced fuel confinement due to the currently necessary joint between the two hemispheres of the outer shell. The gap widens as a result of the excess ablation pressure produced by x rays that penetrate the joint during the drive phase, and this perturbation grows and imprints onto the inner shell during the collision. xRAGE Eulerian radiation-hydrodynamic simulations predict significant reductions in deuterium–tritium fusion yields compared to joint-less simulations when the depth of the outer joint is increased, whereas the performance is less sensitive to the depth of the inner gap. Here we examine the technique of plating the insides of the outer gap with a high-Z material to mitigate the impact of this feature. Gold-plating in quantities comparable to or exceeding the “missing” outer shell mass shows promise toward restoring both implosion symmetry and yield closer to the joint-less levels, and synthetic diagnostics suggest that high-energy x-ray radiographs can capture this shape retention of the inner and outer shells in experiments.

show abstract

Symmetry tuning and high energy coupling for an Al capsule in a Au rugby hohlraum on NIF

Cited by 5 publications

References 13 publications

Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF

Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF

High-volume and -adiabat capsule (“HVAC”) ignition: Lowered fuel compression requirements using advanced Hohlraums

Detrimental effects and mitigation of the joint feature in double shell implosion simulations

Contact Info

Product

Resources

About