FODI at work inspecting an optic between experiments at the National Ignition Facility. Image by Daniel Herchek
(Download Image)Meet the Machines That Matter: The Optics Inspector
LLNL tackles the nation’s toughest security challenges through bold, multidisciplinary science powered by advanced facilities and instruments. In this four-part series, meet the machines that work behind the scenes at the Laboratory to drive discovery, push boundaries, and enable excellence. From inspecting optics and trapping ions to cooling supercomputers and detecting radiation, these are the machines that matter.
What can spot a flaw smaller than a speck of dust from eight meters away, works tirelessly in a vacuum, and is essential to national security experiments at Lawrence Livermore National Laboratory’s National Ignition Facility (NIF)?
Meet the Final Optics Damage Inspection system, or FODI.
Perched on a robot manipulator and armed with a custom telescope, FODI is inserted into the Target Chamber between most NIF experiments to inspect almost 2,000 large optical components in NIF’s 192 beamlines.
NIF’s laser beams travel through up to nine large optics and, in less than the blink of an eye, are converted to ultraviolet light and squeezed to a spot narrower than a human hair. As the last set of optics before entering the chamber, they experience laser rush hour during experiments.
At NIF intensities, it’s not a question of if the optics are damaged, but when. That’s why the FOA runs on something like pit-crew logic. Optics are routinely removed, repaired, and returned through the Optics Recycle Loop, keeping the system ready to deliver the energy that creates extreme pressures and temperatures to spark fusion ignition and advance high-energy-density physics.
FODI’s superpower is its eagle-eyed vision. From eight meters away, it can spot damage sites as tiny as 50 microns. It then hands off those findings to the Optics Inspection Artificial Intelligence software, the command center that tracks the relevant fused-silica and frequency conversion crystal optics in the FOA, whether it is currently installed on NIF or waiting its turn in the recycle process.
The human operators of NIF rely on the Optics Inspection Artificial Intelligence software and supporting databases to track damage progression. They can then deploy mitigation tools like beam blockers—digital mini umbrellas that protect the damage site—or pull the optic for repair.
None of this is gentle work. FODI spends hours at a time operating in a vacuum inside the Target Chamber, a tough environment for mechanical systems. It rarely gets more than a few days off each week.
After more than 15 years in service, the wear is showing. FODI wasn’t designed for repeated removal and reinstallation, but the increase in high-yield experiments has made that necessary. A reboot is on the way through the NIF Sustainment project with a more modern, more neutron-tolerant FODI 2.0.
As NIF pushes toward even higher laser energy and new records, with ten ignition results to date and a record 8.6 megajoules of fusion yield, FODI will be there watching carefully over NIF’s valuable optics. This specialized system, combining precision robotics, advanced imaging, and intelligent analysis, is critical in enabling NIF to operate at the most extreme physical conditions necessary to meet national security priorities.
More Information:
“NIF Sustainment: Ensuring the Next 20 Years of Progress,” NIF & Photon Science News, May 10, 2023
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