Engineering topics

Sagert, Irina

Publications and source records attributed to Sagert, Irina.

3 records

DOE OSTI2024

Beryllium–tungsten graded density inner shells in double shell capsules for improved hydrodynamic stability

The outer surface of the high-Z inner shell in the double shell configuration of inertial confinement fusion experiments experiences Rayleigh–Taylor instability growth during the implosion process due to inverted density and pressure gradients between a highly compressed foam interstitial layer and the accelerating dense inner shell. Graded density layers have long been known to reduce instability growth rates. In this study, we employ high-fidelity radiation hydrodynamic simulations to demonstrate this improved stability when grading beryllium into tungsten. We first characterize the response to L-band preheat of these layers using a newly calibrated radiation drive. While graded layer capsules suffer reduced performance (here, measured as DD neutron yield from a CD foam fuel) in 1D simulations due to reduced kinetic energy coupling and reduced fuel compression, they suffer less of a performance drop when 2D instabilities are accounted for. With the improved stability of graded layers, we explore the performance of capsules with larger fuel radii and thinner shells as a preliminary study to find new designs in which graded layers produce the highest yields.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

H_Burn_Key2_Dshell_CCC: Pre-shot Report

The double shell implosion platform presents an opportunity to explore the dynamics of a burning plasma within a volumetric burn framework. The double shell campaign and the ICF program at Los Alamos National Laboratory (LANL) is focused on achieving burning plasma using an indirectly driven double shell implosion at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL). Double shell implosion is aimed at achieving robust ignition with lower convergence, albeit introducing more engineering and physics complexity due to the intricacies of assembling the capsule. The double shell target is comprised of an outer aluminum ablator shell and an inner high-Z (made of molybdenum or tungsten) pusher shell, separated by a cushion of low-density foam. The outer shell undergoes ablation driven by hohlraum-generated x-rays, which compress the foam to immense pressures, reaching several gigabars. This creates a pressure reservoir that propels the high-Z metal pusher, compressing and heating the deuterium-tritium (DT) liquid fuel to significant densities and temperatures, thereby igniting the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Outer shell symmetry for double shell capsules with aluminum ablators

Double shell targets are a promising potential avenue to obtain robust neutron yield at current laser facilities. Similar to single shell designs, double shells require the symmetric implosion of an ablator in order to uniformly compress and heat a fuel volume, with the goal of achieving thermonuclear burn. Significant differences between double and single shells include the usage of an aluminum ablator as well as a reverse ramp laser pulse. In addition, double shells require a different convergence than single shells for fuel ignition. Numerical implosion studies at various energies with comparisons to experimental outcomes are required to gain confidence that simulations can capture the ablator shape from subscale to full scale. The current work builds on previous implosion experiments conducted at 1-MJ laser energy to con firm achieved ablator symmetry at 1.25 and 1.5 MJ. Average ablator P2 and P4 shapes measured in these experiments are within 5% of the simulated shape, which merits the platforms for further experimental studies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗