Simulations of laser imprint reduction using underdense foams and its consequences on the hydrodynamic instability growth

Olazabal-Loumé, M.; Nicolaï, Ph.; Riazuelo, G.; Grech, M.; Breil, J.; Fujioka, Shinsuke; Sunahara, A.; Борисенко, Н. Г.; Tikhonchuk, V. T.

doi:10.1088/1367-2630/15/8/085033

Cited by 9 publications

(8 citation statements)

References 41 publications

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“…While intensity modulations in the incident laser and development of R-M and R-T instabilities in a shocked shell are well understood and simulated processes, the coupling between the two during the plasma build up period is not. Efforts to understand and mitigate this complex laser imprint phase have been performed using 2-D radiation-hydrodynamics simulations [11,[32][33][34][35]. These simulations routinely approximate the initial plasma formation and laser imprint by using an experimentally derived intensity profile representative of the driving laser to seed the hydrodynamic instabilities in a pre-ioinized plasma.…”

Section: Introductionmentioning

confidence: 99%

Direct-drive measurements of laser-imprint-induced shock velocity nonuniformities

Peebles

Theobald

et al. 2019

Phys. Rev. E

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Perturbations in the velocity profile of a laser-ablation-driven shock wave seeded by speckle in the spatial beam intensity (i.e., laser imprint) have been measured for the first time. Direct measurements of these velocity perturbations were recorded using a two-dimensional (2-D) high-resolution velocimeter probing plastic material shocked by 100-ps picket laser pulse from the OMEGA Laser System. The measured results for experiments with one, two, and five overlapping beams incident on target clearly demonstrate a reduction in long-wavelength (> 25 µm) perturbations with an increasing number of overlapping laser beams, consistent with theoretical expectations. These experimental measurements are crucial to validate radiation-hydrodynamics simulations of laser imprint for laser direct drive inertial confinement fusion research, since they highlight the significant (factor of three) underestimation of the level of seeded perturbation when the microphysics processes for initial plasma formation such as multiphoton ionization are neglected.

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Section: Introductionmentioning

confidence: 99%

Direct-drive measurements of laser-imprint-induced shock velocity nonuniformities

Peebles

Theobald

et al. 2019

Phys. Rev. E

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“…The transmission in PE at 1315 nm wavelength, in fact, is about 90% [18], thus low laser energy is deposited in the thin target and transferred to the plasma. The absorbance in low density foam polyethylene, instead, increases of about a two factor or more [19], thus it permits to enhance the laser energy transfer to the generated plasma, i.e. , increasing both the plasma temperature and the deuteron ion acceleration, enhancing the probability to induce D-D fusion processes.The focal position of the laser with respect to the target surface is crucial.…”

Section: Discussionmentioning

confidence: 99%

Ion Acceleration and D-D Nuclear Fusion in Laser-Generated Plasma from Advanced Deuterated Polyethylene

Torrisi

2014

Molecules

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Deuterated polyethylene targets have been irradiated by means of a 10 16 W/cm 2 laser using 600 J pulse energy, 1315 nm wavelength, 300 ps pulse duration and 70 micron spot diameter. The plasma parameters were measured using on-line diagnostics based on ion collectors, SiC detectors and plastic scintillators, all employed in time-of-flight configuration. In addition, a Thomson parabola spectrometer, an X-ray streak camera, and calibrated neutron dosimeter bubble detectors were employed. Characteristic protons and neutrons at maximum energies of 3.0 MeV and 2.45 MeV, respectively, were detected, confirming that energy spectra of reaction products coming from deuterium-deuterium nuclear fusion occur. In thick advanced targets a fusion rate of the order of 2 × 10 8 fusions per laser shot was calculated.

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“…Indeed, during its propagation through the foam plasma, the laser drives parametric instabilities, such as forward Stimulated Brillouin Scattering 69 leading to an effective smoothing of the hot spot pattern. Due to the low density of the foam, the ionization wave is supersonic and no shock is created, [70][71][72] in contrary to the case of overdense foams.…”

Section: A Experimental Configurationmentioning

confidence: 99%

Progress in indirect and direct-drive planar experiments on hydrodynamic instabilities at the ablation front

et al. 2014

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Understanding and mitigating hydrodynamic instabilities and the fuel mix are the key elements for achieving ignition in Inertial Confinement Fusion. Cryogenic indirect-drive implosions on the National Ignition Facility have evidenced that the ablative Rayleigh-Taylor Instability (RTI) is a driver of the hot spot mix. This motivates the switch to a more flexible higher adiabat implosion design [O. A. Hurricane et al., Phys. Plasmas 21, 056313 (2014)]. The shell instability is also the main candidate for performance degradation in low-adiabat direct drive cryogenic implosions [Goncharov et al., Phys. Plasmas 21, 056315 (2014)]. This paper reviews recent results acquired in planar experiments performed on the OMEGA laser facility and devoted to the modeling and mitigation of hydrodynamic instabilities at the ablation front. In application to the indirect-drive scheme, we describe results obtained with a specific ablator composition such as the laminated ablator or a graded-dopant emulator. In application to the direct drive scheme, we discuss experiments devoted to the study of laser imprinted perturbations with special phase plates. The simulations of the Richtmyer-Meshkov phase reversal during the shock transit phase are challenging, and of crucial interest because this phase sets the seed of the RTI growth. Recent works were dedicated to increasing the accuracy of measurements of the phase inversion. We conclude by presenting a novel imprint mitigation mechanism based on the use of underdense foams. The foams induce laser smoothing by parametric instabilities thus reducing the laser imprint on the CH foil. V C 2014 AIP Publishing LLC. [http://dx.

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Simulations of laser imprint reduction using underdense foams and its consequences on the hydrodynamic instability growth

Cited by 9 publications

References 41 publications

Direct-drive measurements of laser-imprint-induced shock velocity nonuniformities

Direct-drive measurements of laser-imprint-induced shock velocity nonuniformities

Ion Acceleration and D-D Nuclear Fusion in Laser-Generated Plasma from Advanced Deuterated Polyethylene

Progress in indirect and direct-drive planar experiments on hydrodynamic instabilities at the ablation front

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