Studies on the robustness of shock-ignited laser fusion targets

Atzeni, S.; Schiavi, A.; Marocchino, A.

doi:10.1088/0741-3335/53/3/035010

Cited by 51 publications

(64 citation statements)

References 36 publications

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“…This compression shock converges, reflects at its minimum radius, and then expands before colliding with the ignition shock. Full radiation hydrodynamics calculations [3] show that shock ignition is reasonably tolerant of departures from spherical symmetry. This is perhaps surprising since it is known [4,5] that spherically converging shock waves are unstable to perturbations of their surface.…”

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confidence: 98%

Symmetry of Spherically Converging Shock Waves through Reflection, Relating to the Shock Ignition Fusion Energy Scheme

Davie

Evans

2013

Phys. Rev. Lett.

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We examine the properties of perturbed spherically imploding shock waves in an ideal fluid through the collapse, bounce, and development into an outgoing shock wave. We find broad conservation of the size and shape of ingoing and outgoing perturbations when viewed at the same radius. The outgoing shock recovers the velocity of the unperturbed shock outside the strongly distorted core. The results are presented in the context of the robustness of the shock ignition approach to inertial fusion energy. DOI: 10.1103/PhysRevLett.110.185002 PACS numbers: 52.57.Kk, 47.20.Ma, 47.40.Nm, 52.57.Fg Shock ignition [1] is a variant on fast ignition [2] of inertial fusion targets which improves target performance by burning the deuterium-tritium fuel on a lower adiabat (and therefore with less input energy) than is possible using central ignition [1]. Shock ignition occurs as the result of the temperature increase at the surface of collision of two shock waves. The ingoing ''ignition'' shock is the result of a rapid late time increase in driver power and the outgoing shock is the earlier ''compression'' shock. This compression shock converges, reflects at its minimum radius, and then expands before colliding with the ignition shock. Full radiation hydrodynamics calculations [3] show that shock ignition is reasonably tolerant of departures from spherical symmetry. This is perhaps surprising since it is known [4,5] that spherically converging shock waves are unstable to perturbations of their surface.The purpose of this Letter is to study an idealized problem relating to the compression shock, namely, the behavior of finite amplitude perturbations on a converging shock wave, to follow this shock through convergence, reflection at its minimum radius, and then into the expansion phase. We examine the underlying hydrodynamics with a uniform ideal gas, in the absence of heat conduction and other sources and sinks of energy. The relevance to shock ignition is that this approximates the behavior of the compression shock. Pure hydrodynamics is something of a worst case for these perturbed shocks-much of the additional physics will be dissipative and favor greater stability against perturbation growth. The results may also be of interest in the study of the symmetry of supernovae explosions with the proviso that the present work has no input of thermonuclear energy.Previous work has established that during convergence the shock is unstable to perturbations on its surface [4,5], and that during the subsequent blast wave the perturbations are likely to decay [6]. We show that the perturbations are transferred with little change through convergence into expansion, recovering their approximate ingoing form. This ability of the spherical shock waves to recover their ingoing form is at the root of the robustness of shock ignition.Analytic solutions for spherically symmetric converging shocks are used to validate the computer models for these shocks in 1D spherical and 2D axial symmetry. The 2D models then have small perturbations applied ...

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confidence: 98%

Symmetry of Spherically Converging Shock Waves through Reflection, Relating to the Shock Ignition Fusion Energy Scheme

Davie

Evans

2013

Phys. Rev. Lett.

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“…These results have been confirmed by simulations of similar designs by Perkins et al, 812 Terry et al, 820 and Anderson et al 810 for the NIF; Canaud and Temporal 821 and Temporal et al 822 for the Laser M egajoule (LMJ); Ribeyre et al 823,824 and Atzeni et al 825 for HiPER; 806 and Schmitt et al 811,826 and Bates et al 827 for KrF lasers. Earlier work used all-DT designs or wetted-foam ablators, but most recent work has focused on CH-ablator targets for keeping the generation of hot electrons from laser-plasma interactions low during the main drive pulse.…”

Section: A One-dimensional Analysis and Simulationsmentioning

confidence: 62%

“…Figure 15 Given the small stagnation hot-spot radii in SI implosions, low-mode asymmetries may also be problematic, particularly those from target offset and beam geometry. Simulations 810,825 indicate that SI targets can tolerate offsets only of the order of half their stagnation radii, or about 10-15 lm. The beam geometries of facilities like the NIF and LMJ, which are optimized for indirect drive and therefore lack spherical symmetry, have led to "polar-drive" beam-repointing schemes (Sec.…”

Section: B Two-dimensional Hydrodynamicsmentioning

confidence: 99%

Direct-drive inertial confinement fusion: A review

et al. 2015

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The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

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“…In a previous paper [9] we have analyzed a simple all-DT target, driven by pulses with = 0.35 m and total energy of 250-300 kJ. Here, we extend such a study.…”

Section: Introductionmentioning

confidence: 79%

Studies on shock ignition targets for inertial fusion energy

Atzeni

Schiavi

Marocchino

et al. 2013

EPJ Web of Conferences

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Abstract. Shock-ignited inertial fusion targets are studied by one dimensional and two-dimensional numerical simulations. Most of the study refers to the simple all-DT HiPER baseline target (imploded mass of 0.29 mg); both the reference laser wavelength = 0.35 m, and = 0.25 m are considered. The target achieves 1D gain about 80 (120) with total laser energy of 260 kJ (180 kJ) at = 0.35 m (0.25 m). Operating windows for the parameters of the laser ignition spike are described. According to preliminary simulations, gain 80-100 is also obtained by a scaled target (imploded mass of 1.8 mg) driven by 1.5 MJ of green laser light (0.53 m). Two dimensional simulations indicate robustness to irradiation nonuniformities, and high sensitivity to target mispositioning. This can however be reduced by increasing the power of the ignition spike.

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Studies on the robustness of shock-ignited laser fusion targets

Cited by 51 publications

References 36 publications

Symmetry of Spherically Converging Shock Waves through Reflection, Relating to the Shock Ignition Fusion Energy Scheme

Symmetry of Spherically Converging Shock Waves through Reflection, Relating to the Shock Ignition Fusion Energy Scheme

Direct-drive inertial confinement fusion: A review

Studies on shock ignition targets for inertial fusion energy

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