Laser-driven implosion experiments

McCall, Gene H.

doi:10.1088/0032-1028/25/3/001

Cited by 33 publications

(18 citation statements)

References 89 publications

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“…A maximum acceptable particle size for any given fluctuation frequency in the carrier phase can be determined by requiring that the ratio of the energy spectrum of fluctuations of the particulate be within 1% of those of the gas. Figure 3 shows curves of this maximum diameter for pure water droplets in both air and SF 6 . By far, the largest acceleration to be followed by the fog droplets is that following the planar shock wave.…”

Section: Flow-tracking Fidelitymentioning

confidence: 99%

Evolution of a shock-accelerated thin fluid layer

1997

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Multi-exposure flow visualization experiments with laser-sheet illumination provide growth-rate measurement of Richtmyer–Meshkov instability of a thin, perturbed heavy-gas layer embedded in a lower-density gas and accelerated by a planar shock wave. The measurements clearly show the three-stage transition to turbulence of this gas-curtain instability and the single-event coexistence of the three primary flow morphologies discovered previously. The shock-induced circulation for each event is estimated using a simple model based on Richtmyer–Meshkov instability and an infinite linear array of vortex points. These estimates are consistent with simplified flow simulations using a finite-core vortex-blob model.

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Section: Flow-tracking Fidelitymentioning

confidence: 99%

Evolution of a shock-accelerated thin fluid layer

1997

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“…In the presence of the resonance absorption of the laser radiation, such conditions correspond to relatively small values of the parameter I L λ 2 (I L and λintensity and wavelength of laser radiation), which should not exceed the value of 10 14 Wμm 2 /cm 2 . In the middle of the 1980s, analyses of experimental results (McCall et al, 1983;Tan et al, 1983) concerning the compression of spherical targets by a long-wavelength radiation CO 2 lasers have shown that for I L λ 2 ≈ 10 15-17 Wμm 2 /cm 2 and the laser energy above 100 kJ, the dimensional parameters of ICF target and a range of the fast electrons can be chosen in such a way to exclude preheating of the compressed part of the target (Volosevich & Rozanov, 1981;Gus'kov et al, 1983;1987). It was also shown that under these conditions the fast electron energy transfer from the critical density region to more dense plasma areas increases the ablation pressure and thereby plays a positive role in the target compression.…”

Section: Introductionmentioning

confidence: 99%

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²

et al. 2014

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The paper is directed to the study of high-temperature plasma and ablation plasma formation as well as efficiency of the laser energy transfer to solid targets irradiated by laser pulses with intensities of 1–50 PW/cm2 and duration of 200–300 ps, i.e., at conditions corresponding to the characteristics of the laser spike designed to generate the igniting shock wave in the shock ignition concept. The experiments have been performed at Prague Asterix Laser System. The iodine laser delivered 250 ps (full width at half maximum) pulses with the energy in the range of 100–600 J at the first (λ1 = 1.315 µm) and third (λ3 = 0.438 µm) harmonic frequencies. The focal spot radius of the laser beam on the surface of Al or Cu targets made was gradually decreased from 160 to 40 µm. The diagnostic data collected using three-frame interferometry, X-ray spectroscopy, and crater replica technique were interpreted by two-dimensional numerical and analytical modeling which included generation and transport of fast electrons. The coupling parameter Iλ2 was varied in the range of 1 × 1014−8 × 1016 Wμm2/cm2 covering the regimes of weak to intense fast electron generation. The dominant contribution of fast electron energy transfer into the ablation process and shock wave generation was found when using the first harmonic laser radiation, the focal spot radius of 40–100 µm, and the laser energy of 300–600 J.

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“…The complexity introduced by the second dimension was illustrated by Rickard et al, 623 who used a 2-D Fokker-Planck calculation of a 3.5-ps, 0.25-lm laser pulse incident on an exponential density gradient of 3-lm scale length to show that the heat flux is not necessarily parallel to ÀrT e . They found angles of up to 34 between the two vectors. This situation cannot be handled by 2-D nonlocal models or 2-D flux-limiter models in which an equivalent thermal conductivity is obtained using the heat flux and used to solve the 2-D thermal diffusion equation.…”

Section: -91mentioning

confidence: 99%

“…32 Velarde and Carpintero-Santamar ıa 24 give an account of the history of ICF written by its pioneers. Early ICF work was reviewed in papers by Brueckner and Jorna, 33 McCall, 34 and McCrory and Soures. 35 More recently, Rosen 36 provided a useful tutorial and Lindl, 37 while focusing on indirect drive reviewed much of the physics that is common to both approaches.…”

Section: Introductionmentioning

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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Laser-driven implosion experiments

Cited by 33 publications

References 89 publications

Evolution of a shock-accelerated thin fluid layer

Evolution of a shock-accelerated thin fluid layer

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²

Direct-drive inertial confinement fusion: A review

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Laser-driven implosion experiments

Cited by 33 publications

References 89 publications

Evolution of a shock-accelerated thin fluid layer

Evolution of a shock-accelerated thin fluid layer

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm2

Direct-drive inertial confinement fusion: A review

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Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²