Multimode Hydrodynamic Instability Growth of Preimposed Isolated Defects in Ablatively Driven Foils

Area of Science:

• Plasma Physics
• Laser-driven Hydrodynamics
• Materials Science

Background:

• Inertial confinement fusion (ICF) relies on precise capsule fabrication, but inherent nonuniformities can seed hydrodynamic instabilities.
• Understanding the evolution of these defects is crucial for achieving ignition.

Purpose of the Study:

• To systematically study the growth of isolated, localized defects in laser-accelerated plastic foils.
• To investigate defect evolution through ablative Richtmyer-Meshkov and Rayleigh-Taylor instabilities into the nonlinear regime.

Main Methods:

• Utilized the Nike KrF laser facility for controlled experiments on plastic foils with emulated ICF capsule defects.
• Employed face-on X-ray radiography to observe perturbation growth and closure dynamics.
• Conducted radiation hydrodynamic simulations to interpret experimental observations.

Main Results:

• Observed initial growth in perturbation depth and width, followed by closure due to oblique spike growth.
• Detected hollow jetlike Rayleigh-Taylor bubbles expanding from isolated defects on the target rear surface.
• Simulations elucidated the mechanisms behind defect-induced bubble and spike evolution.

Conclusions:

• The study provides the first systematic investigation of isolated defect evolution under ICF-relevant conditions.
• Findings offer critical insights into the behavior of nonuniformities that impact ICF capsule performance.
• The experimental platform enables future studies of multimode perturbation growth in the nonlinear regime.