Shock Ignition Laser-Plasma Interactions in Ignition-Scale Plasmas

Scott, R. H. H.; Glize, K.; Antonelli, L.; Khan, Mobin; Theobald, W.; Wei, M. S.; Betti, R.; Stoeckl, C.; Seaton, A. G.; Arber, T. D.; Barlow, Duncan; Goffrey, T.; Bennett, Keith; Garbett, Warren; Atzeni, S.; Casner, A.; Batani, D.; Li, C.; Woolsey, N. C.

doi:10.1103/physrevlett.127.065001

Cited by 24 publications

(14 citation statements)

References 38 publications

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“…Laser-driven fusion [1][2][3] is a promising approach for the realization of controlled fusion energy. Many laser-driven fusion schemes have been proposed in the past decades, including the indirect-drive central ignition [4][5][6] , the directdrive central ignition [7][8][9] , the hybrid-drive ignition [10][11][12] , the cone-guided fast ignition [13][14][15][16] , the shock ignition [17,18] , the impact ignition [19] and the double-cone ignition (DCI) [20] . In the DCI scheme, the conventional central ignition process is replaced by four progressive processes: quasi-isentropic compression, acceleration, collisional preheating and magnetic field assisted fast ignition.…”

Section: Introductionmentioning

confidence: 99%

Machine-learning guided optimization of laser pulses for direct-drive implosions

Yang

et al. 2022

High Pow Laser Sci Eng

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The optimization of laser pulse shape is of great importance and a major challenge for laser direct-drive implosions. In this paper, we propose an efficient intelligent method to perform the laser pulse optimization via hydrodynamic simulations guided by the genetic algorithm and random forest algorithm. Compared to manual optimizations, the machinelearning guided method is able to efficiently improve the areal density by a factor of 63% and reduce in-flight-aspect-ration by a factor of 30% at the same time. A relationship between the maxium areal density and ion temperature is also achieved by the analysis of the big simulation dataset. This design method has been successfully demonstrated by the 2021 summer Double-Cone Ignition (DCI) experiments conducted on the SG-II upgrade laser facility and has great prospects for the design of other inertial fusion experiments.

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Section: Introductionmentioning

confidence: 99%

Machine-learning guided optimization of laser pulses for direct-drive implosions

Yang

et al. 2022

High Pow Laser Sci Eng

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“…Linear LPI theory does not include the non-linear interaction of many laser-plasma waves with non-thermal particle distributions at a range of densities. Despite these complexities there is evidence, from experiment 27,32 supported by PIC simulation 33 , that stimulated Raman scattering (SRS) off plasma at 10 − 25% of the critical density is the dominant LPI and source of hot electrons in the > 3 × 10 15 W/cm 2 intensity regime.…”

Section: Introductionmentioning

confidence: 99%

“…This is done to investigate the LPI and hot electrons that are generated at > 10 15 W/cm 2 intensities, long density scale lengths ≃ 500µm and electron temperatures ≃ 3keV predicted to occur in SI plasmas 18,27 . Recent experiments conducted in planar or conical geometry at the Omega Facility 41,42 have attempted to infer the fraction of laser energy converted to hot electrons (η) and the temperature of the population (T h ) 32,43,44 . Zhang et al 43 uses a planar target and predicts η < 0.01 in T h ≃ 30keV.…”

Section: Introductionmentioning

confidence: 99%

“…Tentori et al 44 also uses a planar target but predicts η ≃ 0.10 in T h ≃ 30keV. Scott et al 32 uses a conical target and predicts η ≃ 0.025 in T h ≃ 45keV. The discrepancies are significant as the population is at the edge of what will cause acceptable preheat for SI 45 .…”

Section: Introductionmentioning

confidence: 99%

“…This experiment achieved I ≃ 3 × 10 15 W/cm 2 intensities, density scale lengths L n ≃ 600nm and electron temperatures T e ≃ 2.5keV close to the conditions predicted in SI (see Table II). The experiment was carried out with a spherical target and PDD beam geometry as expected for SI (on the NIF) removing the geometric limitations of previous experiments 32,43,44 . It was found in simulation of the solid target direct drive NIF experiment that hot electrons change the shock timing due to deeper target penetration (than the laser) and lead to a modified density profile featuring a larger radius ablation front and a single shock front (in comparison a simulation without hot electrons predicts two separate shocks).…”

Section: Introductionmentioning

confidence: 99%

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Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

et al. 2022

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Shock ignition is a scheme for direct drive inertial confinement fusion that offers the potential for high gain with the current generation of laser facility; however, the benefits are thought to be dependent on the use of low adiabat implosions without laser–plasma instabilities reducing drive and generating hot electrons. A National Ignition Facility direct drive solid target experiment was used to calibrate a 3D Monte Carlo hot-electron model for 2D radiation-hydrodynamic simulations of a shock ignition implosion. The [Formula: see text] adiabat implosion was calculated to suffer a 35% peak areal density decrease when the hot electron population with temperature [Formula: see text] and energy [Formula: see text] was added to the simulation. Optimizing the pulse shape can recover [Formula: see text] of the peak areal density lost due to a change in shock timing. Despite the harmful impact of laser–plasma instabilities, the simulations indicate shock ignition as a viable method to improve performance and broaden the design space of near ignition high adiabat implosions.

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Observation and modelling of stimulated Raman scattering driven by an optically smoothed laser beam in experimental conditions relevant for shock ignition

Cristoforetti

Hüller

Koester

et al. 2021

High Pow Laser Sci Eng

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We report results and modelling of an experiment performed at the TAW Vulcan laser facility, aimed at investigating laser-plasma interaction in conditions which are of interest for the Shock Ignition scheme to Inertial Confinement Fusion, i.e. laser intensity higher than 10 16 W/cm 2 impinging on a hot (T > 1 keV), inhomogeneous and long scalelength preformed plasma. Measurements show a significant SRS backscattering (∼ 4 − 20% of laser energy) driven at low plasma densities and no signatures of TPD/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is dominated by the contribution from the most intense speckles, where SRS gets saturated. Analytical and kinetic simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non linear Landau damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the low density profile justifies the low temperature measured for hot electrons (7 − 12 keV), well reproduced by numerical simulations.

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Shock Ignition Laser-Plasma Interactions in Ignition-Scale Plasmas

Cited by 24 publications

References 38 publications

Machine-learning guided optimization of laser pulses for direct-drive implosions

Machine-learning guided optimization of laser pulses for direct-drive implosions

Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

Observation and modelling of stimulated Raman scattering driven by an optically smoothed laser beam in experimental conditions relevant for shock ignition

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