Beam-pointing verification using x-ray pinhole cameras on the 60-beam OMEGA laser

Area of Science:

• Laser-driven inertial confinement fusion
• High-energy-density physics

Background:

• Accurate beam pointing is crucial for efficient energy coupling in inertial confinement fusion (ICF) experiments.
• The OMEGA laser system utilizes multiple beams to irradiate spherical targets, demanding precise alignment for optimal performance.

Purpose of the Study:

• To develop and implement advanced algorithms for precise evaluation of beam-pointing accuracy on the OMEGA laser system.
• To enhance the analysis of x-ray emission data for improved target illumination uniformity assessment.

Main Methods:

• Irradiation of a 4 mm diameter gold-coated spherical target with approximately 23 kJ of laser energy on the OMEGA laser system.
• Acquisition of x-ray emission data from 60 beam spots using up to ten x-ray pinhole cameras.
• Development of new algorithms including subpixel edge-finding, 3D back-propagation of pixel locations, and Fast Fourier Transform (FFT) based de-noising.

Main Results:

• Improved accuracy in determining the center of the spherical target with subpixel precision.
• Significant enhancement of the signal-to-noise ratio in the x-ray emission data.
• Accurate evaluation of laser-drive illumination uniformity and decomposition into lower-order modes (1-10) based on refined beam-pointing analysis.

Conclusions:

• The newly developed algorithms significantly improve the accuracy of beam-pointing evaluation in ICF experiments.
• Enhanced understanding of illumination uniformity on the target surface, critical for optimizing fusion yields.
• The methodology provides a robust framework for future high-power laser experiments requiring precise beam control.