Precision shock tuning on the national ignition facility.

Area of Science:

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

Background:

• Achieving fusion power gain requires compressing deuterium-tritium fuel to high areal density (ρR).
• Ignition implosions at the National Ignition Facility (NIF) use precisely timed shock waves to achieve this compression.
• Previous implosions faced challenges with fuel entropy and adiabat control.

Purpose of the Study:

• To perform precision tuning experiments on NIF implosions using optical diagnostics.
• To directly measure the strength and timing of four shock waves inside a hohlraum-driven capsule.
• To assess the impact of improved shock timing on fuel compression and adiabat.

Main Methods:

• Conducted precision tuning experiments on NIF using optical diagnostics.
• Measured shock wave strength and timing within a cryogenic liquid-deuterium-filled capsule.
• Analyzed deuterium-tritium layered capsule implosions to evaluate compression.

Main Results:

• Demonstrated a significant decrease in adiabat compared to previously untuned implosions.
• Achieved the highest fuel compression (ρR~1.0 g/cm²) to date, exceeding previous records by over 3x.
• Observed the 4th shock velocity to be 20% slower than predicted by numerical simulations.

Conclusions:

• Precision shock timing is crucial for reducing fuel adiabat and increasing compression in NIF implosions.
• The experimental results validate the importance of shock timing for fusion energy gain.
• Discrepancies in 4th shock velocity highlight areas for improvement in NIF simulation models.