Measurement of Dark Ice-Ablator Mix in Inertial Confinement Fusion

Area of Science:

• Nuclear Fusion Science
• Plasma Physics
• Materials Science

Background:

• Inertially confined fusion relies on precise implosions of cryogenic fuel capsules.
• Understanding the mixing of ablator material into the fuel is critical for achieving fusion ignition.
• Previous studies focused on mix within the hot spot, but the role of cooler, surrounding mix was less understood.

Purpose of the Study:

• To measure and characterize the ice-ablator mix at stagnation in cryogenically layered capsule implosions.
• To investigate the impact of ice layer thickness on mix near the inner ablator interface.
• To differentiate between 'dark' mix and 'hot' mix and assess their origins and implications.

Main Methods:

• Performed experiments on inertially confined, cryogenically layered capsule implosions.
• Conducted an ice layer thickness scan, using layers thinner than typical ignition experiments.
• Analyzed the stagnation products to quantify atomically mixed ablator material.

Main Results:

• The majority of atomically mixed ablator material was identified as "dark" mix.
• "Dark" mix originates from the ice-ablator interface instability.
• Increasing the initial ice layer thickness significantly reduced ice-ablator mix in the hot-spot boundary region.

Conclusions:

• "Dark" mix, seeded by interface instability, is a primary component of ablator mix in these implosions.
• This "dark" mix resides in the cooler fuel regions surrounding the hot spot.
• Thicker ice layers are effective in mitigating ice-ablator mix at the hot-spot boundary, potentially improving fusion performance.