A fully nonlinear sharp-boundary model of the ablative Rayleigh-Taylor instability is derived and closed in a similar way to the self-consistent closure of the linear theory. It contains the stabilizing effect of ablation and accurately reproduces the results of 2D DRACO simulations. The single-mode saturation amplitude, bubble and spike evolutions in the nonlinear regimes, and the seeding of long-wavelength modes via mode coupling are determined and compared with the classical theory without ablation. Nonlinear stability above the linear cutoff is also predicted.

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Here, a model for the nonlinear Rayleigh-Taylor instability (RTI) of a steady ablation front based on a sharp boundary approximation is presented. The model includes the effect of mass ablation and represents a basic tool for investigating many aspects of the nonlinear ablative RTI relevant to inertial confinement fusion. The single mode analysis shows the development of a nonlinear exponential instability for wave numbers close to the linear cutoff. Such a nonlinear instability grows at a rate faster than the linear growth rate and leads to saturation amplitudes significantly larger than the classical value 0.1λ. We also found that linearly stable perturbations with wave numbers larger than the linear cutoff become unstable when their initial amplitudes exceed a threshold value. The shedding of long wavelength modes via mode coupling is much greater than predicted by the classical RTI theory. The effects of ablation on the evolution of a front of bubbles is also investigated and the front acceleration is computed.

The heavy ion beam (HIB) indirectly driven compression of a small amount of DT fuel, and its fast ignition by a beam of laser accelerated protons (PB) is considered (Roth M. et al 2001 Phys. Rev. Lett. 86 436). First, a representative working point (0.8 mg of DT at 400 g cm−3) has been derived analytically from the energy balance of an hypothetical power plant. Second, through self-consistent two-dimensional radiation hydrodynamic simulations with the MULTI code (Ramis R. et al 1988 Comput. Phys. Commun. 49 475) we define and optimize a HIB-driven hohlraum target to produce the above conditions; also, with ignition simulations, we determine the thermonuclear yield (≃83 MJ) and the minimum PB energy (≃33 kJ) needed to ignite the asymmetrically compressed fuel. The target is found to be a factor 5 less sensitive to implosion asymmetries than a conventional central spot one. This allows us to reduce the hohlraum size (≃6 mm), improve the driver coupling, reduce the compression energy to the 0.8–1.2 MJ range, and have enough clearance for the installation of the PB converter foil at distances (3–4 mm) appropriate for an efficient ignition.

Abstract. A critical aspect of predicting soil organic carbon (SOC) concentrations is the lack of available soil information; where information on soil characteristics is available, it is usually focused on regions of high agricultural interest. To date, in Chile, a large proportion of the SOC data have been collected in areas of intensive agricultural or forestry use; however, vast areas beyond these forms of land use have few or no soil data available. Here we present a new SOC database for the country, which is the result of an unprecedented national effort under the framework of the Global Soil Partnership. This partnership has helped build the largest database of SOC to date in Chile, named the Chilean Soil Organic Carbon database (CHLSOC), comprising 13 612 data points compiled from numerous sources, including unpublished and difficult-to-access data. The database will allow users to fill spatial gaps where no SOC estimates were publicly available previously. Presented values of SOC range from 6×10-5 % to 83.3 %, reflecting the variety of ecosystems that exist in Chile. The database has the potential to inform and test current models that predict SOC stocks and dynamics at larger spatial scales, thus enabling benefits from the richness of geochemical, topographic and climatic variability in Chile. The database is freely available to registered users at https://doi.org/10.17605/OSF.IO/NMYS3 (Pfeiffer et al., 2019b) under the Creative Commons Attribution 4.0 International Public License.

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We consider the symmetry of cylindrical implosions of laser targets with parameters corresponding to experiments proposed for the LIL laser facility at Bordeaux: eight laser beams in octahedrical configuration, delivering a total of 50 kJ of 0.35 (xm laser light in 5 ns, impinging on 1.26 mm diameter polystyrene cylindrical shells filled with deuterium at 30 bar and 5.35 mg cm" 3 ; this configuration allows to place diagnostics along the symmetry axis to evaluate directly the uniformity of implosion. Numerical studies have been carried out by using the hydrodynamic computer codes MULTI and CHIC, including one-dimensional, and two-dimensional R-Z and R-6 simulations. Deuterium is compressed into a 1 mm long and 50 |xm diameter filament, with density ranging from 2 to 6 g cm -3 and temperatures above 1000 eV. In spite of the reduced numbers of beams, a good symmetry can be achieved with a careful choice of the irradiation pattern. The heat transport smoothing between laser absorption zone and ablation layer plays a fundamental role in the attenuation of residual non-uniformities. Also, it has been found that the radiation transport determines the radial structure of the compressed filament.