Subpercent-Scale Control of 3D Low Modes of Targets Imploded in Direct-Drive Configuration on OMEGA

Area of Science:

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

Background:

• Direct-drive inertial confinement fusion (ICF) relies on precise implosion symmetry.
• Target modes represent deviations from a perfectly spherical implosion, impacting fusion yield.
• Understanding and mitigating these modes is crucial for achieving ignition.

Purpose of the Study:

• To quantify target modes 1, 2, and 3 during the acceleration phase of direct-drive ICF.
• To identify the contributing factors to these target modes.
• To demonstrate a method for reducing low-mode asymmetries in low-adiabat implosions.

Main Methods:

• Utilized multiple self-emission X-ray images for tomographic reconstruction of target modes.
• Analyzed mode components related to laser beam-energy balance and static physical effects.
• Employed adjustments to the laser beam-energy balance to compensate for static modes.

Main Results:

• Identified two primary components contributing to target modes 1, 2, and 3.
• The first component showed a linear correlation with laser beam-energy balance.
• The second component was static, attributed to beam mistiming, mispointing, and energy uncertainties.
• Successfully reduced low modes in low-adiabat implosions from 2.2% to 0.8%.

Conclusions:

• Laser beam-energy balance is a key factor in controlling dynamic target modes.
• Static imperfections significantly influence target mode development.
• Active compensation of static modes via beam-energy balance adjustment is an effective strategy for improving implosion symmetry and performance.