Designs for highly nonlinear ablative Rayleigh-Taylor experiments on the National Ignition Facility

Abstract

We present two designs relevant to ablative Rayleigh-Taylor instability in transition from weakly nonlinear to highly nonlinear regimes at the National Ignition Facility [E. I. Moses, J. Phys.: Conf. Ser. 112, 012003 (2008)]. The sensitivity of nonlinear Rayleigh-Taylor instability physics to ablation velocity is addressed with targets driven by indirect drive, with stronger ablative stabilization, and by direct drive, with weaker ablative stabilization. The indirect drive design demonstrates the potential to reach a two-dimensional bubble-merger regime with a 20 ns duration drive at moderate radiation temperature. The direct drive design achieves a 3 to 5 times increased acceleration distance for the sample in comparison to previous experiments allowing at least 2 more bubble generations when starting from a three-dimensional broadband spectrum.

Turbulent hydrodynamics experiments in high energy density plasmas: scientific case and preliminary results of the TurboHEDP project

“…Despite a certain level of nonlinearity, the loss of memory of initial conditions (one of the criteria of a turbulent flow) does not happen in these experiments. Limitations are primary due to the lack of sufficient laser energy to sustain steady shock conditions long time enough to enter the highly nonlinear stage of the RTI [9,10] .…”

“…Radiative shocks are a fundamental aspect [10,36] are shown to illustrate the increasing level of nonlinearity of the flows expected on each facility. of astrophysical and high energy density systems because any fast enough shock wave becomes radiative [50,51] .…”

“…The Turbulent hydrodynamics experiments in high energy density plasmas: preliminary results of the TurboHEDP project Discovery Science Ablative RTI proposal on NIF was devoted from 2013 to 2015 to the study of the highly nonlinear stage of the ablative RTI [9,10] . Thanks to a 20-ns-shaped laser pulse and ∼266 kJ of laser energy, a bubble-merger regime for RTI at ablation front has been evidenced for the first time in indirect drive starting from a 2D broadband preimposed modulation [36][37][38] .…”

“…[6] for a review), turbulent HED plasma flows were just approached very recently [8] . This is mainly due to a lack of laser energy to sustain HED flows for a sufficiently long time to transition to a turbulent stage [9,10] . The next generation of HED laboratory plasma experiments to be performed on the NIF [11] and LMJ-PETAL [12,13] places us at the frontier of a new regime in physics.…”

Implosion Simulation by Hydro Code Coupled with Laser Absorption using New Raytrace Algorithm

“…Uniformity of irradiation is one of the most important issues to efficiently implode the fuel. In general, the ablation surface and the fuel-shell contact interface of the imploding target are Rayleigh-Taylor unstable [2][3][4]. Thus, perturbations on the target surface induced by the non-uniformity of the irradiation grow drastically, which degrades the implosion performance [5].…”