X-ray diffraction at the National Ignition Facility

Area of Science:

• High-pressure physics
• Materials science
• X-ray diffraction

Background:

• Studying materials under extreme pressures is crucial for understanding planetary interiors and inertial confinement fusion.
• Existing methods for in situ diffraction at extreme pressures are limited.

Purpose of the Study:

• To report an experimental platform for in situ powder diffraction of dynamically compressed solids.
• To enable determination of crystal structure, density, and texturing at extreme pressures.

Main Methods:

• Ramp compression of thin samples sandwiched between tamper layers using laser irradiance.
• High-precision velocimetry for pressure history determination.
• Pulsed X-ray diffraction using laser-illuminated metal foils, with selectable wavelengths.
• Image plate detectors for recording diffracted signals.
• Analytic corrections for diffraction angle uncertainties and nonlinear background subtraction algorithms.

Main Results:

• Successful implementation of the experimental platform at the National Ignition Facility.
• Achieved dynamic compression up to 2 TPa (20 Mbar).
• Demonstrated ability to determine crystal structure, density, and strain-induced texturing.
• Observed diffraction lines at low signal-to-background ratios (few percent).

Conclusions:

• The developed platform provides unprecedented capabilities for in situ X-ray diffraction of materials under extreme dynamic compression.
• This research advances the understanding of material behavior at pressures relevant to astrophysics and fusion energy.