NIF is the hottest place on Earth during the shortest moments during an experiment. Now it can be one of the brightest places thanks to Advanced Radiographic Capability (ARC), NIF’s laser within a laser.
How this is possible and how it is measured is detailed in the cover story of the December 2025 issue of Physics of plasmas“Development and scaling of MeV X-ray radiography in NIF-ARC.”
“This paper is the culmination of 13 NIF experiments over five years of data collection, experiment analysis, modeling, and diagnostic refinement,” said LLNL physicist Dean Rusby, first author of the paper. “We are able to create and measure a MeV X-ray source that cannot be done anywhere else in the world.”
ARC compresses two of the laser facility’s beamlines to deliver kilojoules of laser energy in picoseconds. ARC is currently the world’s highest energy short pulse laser. Using this intense burst of energy, ARC creates high-energy (MeV) X-ray x-rays of materials of interest. These experiments help scientists understand how these materials react to extreme conditions.
This work establishes the technological foundation for a future capability that would x-ray explosive-driven hydrodynamics experiments on a sub-microsecond time scale, such as those conducted in LLNL Site 300. The benefit of a laser focus is greater spatial resolution over current high-energy flash X-ray techniques.
This article follows LLNL research published in Physics of plasmas in 2023. LLNL scientist Shaun Kerr was the lead author of that paper, “Development of a bright MeV photon source with composite parabolic concentrator objectives at the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) without lasers,” which included Rusby.
When taking x-rays of moving objects, brightness (the number of photons generated by the x-ray source and the size of the source) is important. The brighter the x-ray source and the smaller the source size, the clearer the image and the finer the details. Over the past five years, Rusby and his colleagues optimized the generation of MeV X-rays with the ARC laser system, but one of the challenges was measuring MeV X-rays.
“From the first shots, we knew that NIF-ARC generated a lot of MeV X-rays,” Rusby said. “But diagnostics to measure and characterize MeV X-rays were not yet available. Detecting and diagnosing high-energy
Combining existing NIF gamma reaction history diagnostics and existing positron, proton, and electron spectrometers with newly implemented nuclear activation diagnostics enabled characterization.
The x-ray samples for the experiments were 2 cm lead balls with interior waves of a characteristic size of hundreds of microns. In some experiments, the target was placed behind a 1–3 cm layer of tungsten as an additional challenge. Both lead and tungsten are extremely dense materials, making imaging difficult.
With the help of modeling and simulation, the researchers also tested different experimental setups within the NIF target chamber. The best images were obtained when objects were placed along the line of sight of the ARC laser axis, which required the development of new sample and diagnostic holders.
The researchers are now working to further optimize the process, including working at smaller spatial scales, reducing the spatial resolution to about 10 microns.
The research was funded with funds from the National Nuclear Security Administration. Co-authors include Rusby and Kerr, along with Lawrence Livermore National Laboratory scientists David Alessi, MB Aufderheide, Jeff Bude, G. Cochran, JM Di Nicola, DN Fittinghoff, MP Hill, Dan Kalantar, A. Kemp, SF Khan, T. Lanier, Andrew MacPhee, D. Martinez, JJ Mcloughlin, N.H. Nguyen, S. Patankar, M. Prantil, S. Stadermann, S.C. Wilks, GJ Williams and Andrew Mackinnon. Other collaborators include A. Aghedo of Lawrence Livermore National Laboratory and the Department of Physics at Florida A&M University, and M. Freeman, K. Meaney, P. Volegov and C. H. Wilde of Los Alamos National Laboratory, as well as Scott Vonhof of General Atomics in San Diego.
More information:
“ARC experimental results provide a pleasant surprise” News about photon science and NIF, March 23, 2020
“Focus lenses provide a 10x performance increase over NIF ARC” News about photon science and NIF, February 12, 2020
“NIF in focus: Inside the ARC laser” (Video), News about photon science and NIF, September 19, 2019
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