Observation of Secular Growth Dominated Dynamics in X-Ray Driven Foils

Area of Science:

• Plasma Physics
• High-Energy-Density Physics
• Nuclear Fusion

Background:

• Achieving ignition in inertial confinement fusion (ICF) requires precise control over hydrodynamic perturbations.
• Seeding and growth of these perturbations, particularly Rayleigh-Taylor instabilities, are critical factors in ICF target performance.

Purpose of the Study:

• To investigate the behavior of hydrodynamic perturbations during the acceleration phase of planar foils in ICF.
• To identify novel phenomena related to perturbation seeding and growth relevant to ICF ignition and high gain.

Main Methods:

• Face-on radiography of planar foils with preimposed sinusoidal ripples.
• Radiation-hydrodynamic simulations.
• Development of a simple analytical model to interpret simulation results.

Main Results:

• Observed a novel phase inversion of perturbations at the ablation front during foil acceleration.
• Identified a secular, nonexponential growth-dominated regime prior to quasisteady acceleration.
• Discovered a freeze-out-like phenomenon where perturbation growth temporarily ceases.

Conclusions:

• The findings advance the fundamental understanding of Rayleigh-Taylor seeding in ICF implosions.
• The identified phenomena offer insights for designing advanced, high-gain ICF targets.
• Control over perturbation seeding and growth is key to successful ICF.