Ride the Optics Recycle Loop with the Big Ideas Lab Podcast

If LLNL’s National Ignition Facility (NIF) was a race car, it would run at the redline most of the time. And NIF’s optics bear the brunt of that stress.

Throughout the beamline, thousands of optics, many 40-centimeter square in size, amplify, transmit, reflect, change wavelength, or focus the lasers as they travel nearly a kilometer to the Target Chamber. To achieve laser energy as high as 2.2 megajoules, NIF was designed and built in a way to manage some level of laser damage on the optics nearly every time the laser fires.

NIF’s optical components were also designed to be quickly removed, refurbished, and reinstalled—a process called the Optics Recycle Loop. In the next episode of the Big Ideas Lab Podcast, we take a ride along this loop of continuous innovation and ingenuity. Listen on Apple or Spotify.

“The ability for NIF to operate at a certain rate, how many shots we can take, the power and energy of those shots—it’s all linked to the rate at which we can recycle components and place them back on the facility,” says Tayyab Suratwala, Program Director for Optics and Materials Science.

When the NIF laser fires, the laser beam intensity is so extreme it can remove material from the surface of the optics, leaving behind damage sites as small as 5-10 microns. If left unchecked, these damage sites can grow exponentially, quickly rendering the optic unusable.

Every week, as many as 40 of NIF’s large optics are removed for refurbishment while an equal number of freshly refurbished optics are installed on the system. In the 15-plus years that NIF has been operating, scientists and engineers have refined and advanced the Optics Recycle Loop as well as the quality of incoming new optics to enable more experiments with ever-increasing laser energy.

The optics are protected through a myriad of novel methods, including casting a tiny shadow over damage sites and using AI and automated microscopes to inspect, analyze, and mitigate damage sites. And as the NIF laser energy goes up, the scientists and engineers discover new ways optics are damaged, followed by new ways to mitigate the damage.

“It’s a really interesting set of physical phenomena that occur every time you get laser damage,” says Wren Carr, Science and Technology Leader for the Optical and Material Science and Technology Group. “For the laser, it’s a big nuisance but scientifically it’s just fascinating.”

In this episode, you’ll hear much more from Suratwala, Carr, and Laura Kegelmeyer, who led the NIF Optics and Inspection and Data Management team, as they explain the science and discovery behind the NIF Optics Recycle Loop. Listen on Apple or Spotify.

More Information:

"Optics, Advancing the Boundaries of Optics Science"

"NIF Hits 10,000 Optics Recycle Milestone," NIF & Photon Science News, Jan. 9, 2020

"Automation Speeds and Smooths NIF’s Optics Recycle Loop," NIF & Photon Science News, Oct. 11, 2017

"Video: Take a Ride Along NIF's Optics Recycle Loop," LLNL Video, Oct. 11, 2017

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