Laser-driven betatron x rays for high-throughput imaging of additively manufactured materials

Abstract

Betatron x rays from a laser wakefield accelerator provide a new avenue for high-resolution, high-throughput radiography of solid materials. Here, we demonstrate the optimization of betatron x rays for three-dimensional tomography of defects in additively manufactured (AM) alloys at a repetition rate of 2.5 Hz. Using the Advanced Laser Light Source in Varennes, Qc, we characterized the x-ray energy spectrum, spatial resolution, beam stability, and emission length from three different gas targets {He, N2, and He–N2 [He (99.5%) + N2 (0.5%)] mixture} to determine the conditions for optimized imaging resolution with minimized acquisition time. Mixed He–N2 produced the highest x-ray critical energy (19 ± 5) keV and average brightness (⁠~ 3.3 x 10¹⁰ photons/s/mm2/mrad2/0.1% BW) vs pure N2 gas (12 ± 4 keV and ~1.6 x 10¹⁰ photons/s/mm2/mrad2/0.1% BW). The mixed gas demonstrated the best beam stability and pointing compared to pure He gas. The optimization of betatron sources at 2.5 Hz for high-resolution imaging of micrometer-scale defects in AM alloys will enable high-throughput data collection, accelerating the characterization of complex mechanical deformation processes in these materials.

DOI: https://doi.org/10.1063/5.0221606