Long duration X-ray drive hydrodynamics experiments relevant for laboratory astrophysics

Abstract

a b s t r a c tThe advent of high-power lasers facilities such as the National Ignition Facility (NIF), and the Laser Megajoule (LMJ) in the near future, opens a new era in the field of High Energy Density Laboratory Astrophysics. These versatile laser facilities will provide unique platforms to study the rich physics of nonlinear and turbulent mixing flows. The extended laser pulse duration could be harnessed to accelerate targets over much larger distances and longer time periods than previously achieved. We report on the first results acquired on NIF with the ablative RayleigheTaylor Instability (RTI) platform. A 20-ns Xray drive is tailored to accelerate planar modulated samples into the highly-nonlinear bubble merger regime. Based on the analogy between flames front and ablation front, highly nonlinear RTI measurements at ablation front can provide important insights into the initial deflagration stage of thermonuclear supernova of Type Ia. We also report on an innovative concept used to create even longer drive on multi-beam laser facilities. The multi-barrel hohlraum (Gattling Gun) approach consists, here, of three adjacent cavities, driven in succession in time. This novel concept has been validated on the Omega EP laser system. The three cavities were irradiated with three 6e10 ns pulse UV beams and a 30 ns, 90 eV Xray radiation drive was measured with the time-resolved X-ray spectrometer mDMX. This concept is promising to investigate the pillar structures in the Eagle Nebula or for photoionization studies which require a steady light source of sufficient duration to recreate relevant physics.

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

“…Reaching a turbulent regime for RTI at a classical interface requires accelerating samples over timescales of tens to a hundred nanoseconds of drive, with velocities of a few tens and sample lateral size of a few millimeters to avoid the detrimental effects of lateral rarefaction waves. Accelerating samples over such a long time with X-ray drive (even with the recently developed multi-barrel hohlraum concept [39, 40] ) without stagnation effects seems difficult. Direct-drive (DD) experiments are the right solution and constitute the heart of the TurboHEDP project.…”

Long-duration planar direct-drive hydrodynamics experiments on the NIF

“…To do so requires timescales of tens to a hundred nanoseconds of drive, with velocities of a few tens μm ns −1 and sample lateral size of a few millimeters to avoid the detrimental effects of lateral rarefaction waves. Accelerating samples over such long time duration with a hohlraum generated x-ray drive (even multibarrel hohlraums [36,37]) without stagnation effects seems difficult. It has been known for years that significant late-time hohlraum internal pressures affect the hydrodynamics of HED experiments [38].…”

Formation Mechanism of Laser-driven Magnetized “Pillars of Creation”

“…Over the past two decades, laboratory astrophysics has become an important tool in astrophysics research (Remington et al 1999(Remington et al , 2006Lebedev et al 2019), and it can help us to investigate the individual specific factor on the formation of pillars under the conditions of scaling laws (Ryutov et al 1999(Ryutov et al , 2001. A novel experiment scheme was proposed to create a long-duration X-ray source to model the UV radiation produced by O stars (Casner et al 2015). Then this X-ray source was used to simulate the shielding model in OMEGA and the National Ignition Facility (NIF; Kane et al 2015;Pound 2017).…”

“…These simulation results also provide information for future experimental designs. To mimic the UV radiation in the Eagle Nebula, a long-duration X-ray source can be achieved through an array of small laser-driven cavities (Casner et al 2015). A low-density foam with preexisting spherical dense clumps is illuminated by the X-rays, and three materials (pure plastic (CH), doping aluminum (Al), and doping gold (Au)) foam targets are used in our RMHD simulations to study the radiation-cooling effect.…”