Improved laser-beam uniformity using the angular dispersion of frequency-modulated light

Skupsky, S.; Short, R. W.; Kessler, T. J.; Craxton, R. S.; Letzring, S.; Soures, J. M.

doi:10.1063/1.344101

Cited by 722 publications

(302 citation statements)

References 4 publications

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“…However, the increase of the growth rate is relatively small for high-intensity laser light ). Laser smoothing techniques, such as induced spatial coherence (ISI) (Lehmberg et al 1987) and smoothing by spectral dispersion (SSD; Skupsky et al 1989), are implemented to reduce laser imprinting in ICF. also show a reduction in the growth rate by applying high-frequency modulation of the incident laser light.…”

Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Nishihara

Wouchuk

Matsuoka

et al. 2010

Phil. Trans. R. Soc. A.

129

128

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A theoretical framework to study linear and nonlinear Richtmyer-Meshkov instability (RMI) is presented. This instability typically develops when an incident shock crosses a corrugated material interface separating two fluids with different thermodynamic properties. Because the contact surface is rippled, the transmitted and reflected wavefronts are also corrugated, and some circulation is generated at the material boundary. The velocity circulation is progressively modified by the sound wave field radiated by the wavefronts, and ripple growth at the contact surface reaches a constant asymptotic normal velocity when the shocks/rarefactions are distant enough. The instability growth is driven by two effects: an initial deposition of velocity circulation at the material interface by the corrugated shock fronts and its subsequent variation in time due to the sonic field of pressure perturbations radiated by the deformed shocks. First, an exact analytical model to determine the asymptotic linear growth rate is presented and its dependence on the governing parameters is briefly discussed. Instabilities referred to as RM-like, driven by localized non-uniform vorticity, also exist; they are either initially deposited or supplied by external sources. Ablative RMI and its stabilization mechanisms are discussed as an example. When the ripple amplitude increases and becomes comparable to the perturbation wavelength, the instability enters the nonlinear phase and the perturbation velocity starts to decrease. An analytical model to describe this second stage of instability evolution is presented within the limit of incompressible and irrotational fluids, based on the dynamics of the contact surface circulation. RMI in solids and liquids is also presented via molecular dynamics simulations for planar and cylindrical geometries, where we show the generation of vorticity even in viscid materials.

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Section: (E) Rm-like Instabilities and Ablative Rmimentioning

confidence: 99%

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Nishihara

Wouchuk

Matsuoka

et al. 2010

Phil. Trans. R. Soc. A.

129

128

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“…Son profil moyen correspond au besoin. Mais son profil réel est en fait très perturbé car il contient des figures de tavelure La technique de lissage est détaillée dans de nombreux documents [11,12,13,14]. La technique de lissage mise en oeuvre sur la LIL et le LMJ est le lissage SSD (Smoothing by Spectral Dispersion).…”

Section: Le Lissage Optique Sur La Lilunclassified

Métrologie des faisceaux et de la tache focale de la LIL

Garrec¹,

Di-Nicola²,

Beau³

2006

J. Phys. IV France

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“…In the direct-drive experiments described here, distributed phase plates, 23 polarization smoothing using birefringent wedges, 24 and 1-THz, two-dimensional smoothing by spectral dispersion 25 were applied to smooth the OMEGA laser beams in order to enhance implosion uniformity and the nuclear reaction rate. Three types of capsules were used to study implosions with a wide range of areal densities.…”

Section: Methodsmentioning

confidence: 99%

Using nuclear data and Monte Carlo techniques to study areal density and mix in D2 implosions

et al. 2005

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Measurements from three classes of direct-drive implosions at the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] were combined with Monte-Carlo simulations to investigate models for determining hot-fuel areal density (ρR hot ) in compressed, D 2 -filled capsules, and to assess the impact of mix and other factors on the determination of ρR hot . The results of the Monte-Carlo calculations were compared to predictions of simple commonly used models that use ratios of either secondary D 3 He proton yields or secondary DT neutron yields to primary DD neutron yields to provide estimates ρR hot,p or ρR hot,n , respectively, for ρR hot . For the first class of implosions, where ρR hot is low (≤ 3 mg/cm 2 ), ρR hot,p and ρR hot,n often agree with each other and are often good estimates of the actual ρR hot . For the second class of implosions, where ρR hot is of order 10 mg/cm 2 , ρR hot,p often underestimates the actual value due to secondary proton yield saturation. In addition, fuel-shell mix causes ρR hot,p to further underestimate, and ρR hot,n to overestimate, ρR hot . As a result, values of ρR hot,p and ρR hot,n can be interpreted as lower and upper limits, respectively. For the third class of implosions, involving cryogenic capsules, secondary protons and neutrons are produced mainly in the hot and cold fuel regions, respectively, and the effects of the mixing of hot and cold fuel must be taken into account when interpreting the values of ρR hot,p and ρR hot,n . From these data sets, we conclude that accurate inference of ρR hot requires comprehensive measurements in combination with detailed modeling. a) Also visiting Senior Scientist,

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Improved laser-beam uniformity using the angular dispersion of frequency-modulated light

Cited by 722 publications

References 4 publications

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Richtmyer–Meshkov instability: theory of linear and nonlinear evolution

Métrologie des faisceaux et de la tache focale de la LIL

Using nuclear data and Monte Carlo techniques to study areal density and mix in D2 implosions

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