July 10, 2024
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When Experiments Go Quiet: Maintaining the National Ignition Facility

By Patricia Koning,[email protected],(925) 423-4332

For two weeks last April, the lasers at Lawrence Livermore National Laboratory’s National Ignition Facility (NIF) stopped firing. Experiments may have been on pause, but the facility was anything but quiet.

“To do world-class science, you need a world-class facility,” said Stanley Sommer, Laser Systems Engineering and Operations deputy division leader. “And you can’t just maintain that facility, you must anticipate problems and seek out improvements.”

The premier tool of the science-based Stockpile Stewardship Program, NIF has been exceptionally productive and reliable since experiments began 15 years ago. The experimental success rate is over 95 percent, with fewer than 30 days of unplanned downtime in more than 3,500 days of shot operations.

“When most people think of NIF, they think of the big experiments,” Sommer said. “But the work behind the scenes is equally heroic—maintaining and improving this incredible facility, to ensure it continues to deliver. And it’s truly a team effort. Reliability is everyone’s responsibility.”

To that end, experiments are paused three times a year to focus on maintenance and improvements, which is what happened last April. This is called Facility Maintenance and Refurbishment, or FM&R, and it lasts from one to three weeks. Teams working on all parts of the facility execute more than 220 carefully orchestrated tasks, often in normally inaccessible areas, like inside the beamlines or Target Chamber.

Sommer likens it to a pit stop during a Formula One race. “You’ve got to get things on and off the racecar in a specific order, and the people working on different aspects must choreograph their work,” he said. “And that racecar must be ready to go at full throttle. That’s how it is with NIF. So many people are relying on reliable systems for experimental results, so we have to execute perfectly.”

Sustainment and FM&R

For most of the year, experiments run on NIF five days a week, with two days set aside for maintenance and to prepare for the next week’s experiments. This includes optics exchanges, diagnostic setup, and minor repairs.

Sommer, who is also the NIF Facility and Infrastructure Systems section manager, has been with NIF from the start. “Early on we recognized that two days a week for impactful maintenance and repairs wasn’t enough time,” he said. “There were certain activities that we couldn’t integrate with the experimental schedule.”

FM&R periods are for more complex activities, like exchanging one of NIF’s cryopumps. Recently, those more complex activities include critical elements of NIF sustainment, a five-year plan that identified comprehensive maintenance on key systems—urgent refurbishments and replacement of obsolete equipment.

Stanley Sommer, Laser Systems Engineering and Operations deputy division leader
FM&R periods are one of Stanley Sommer’s favorite times at NIF, when the team is able to perform important maintenance and repairs to support reliable performance of the systems.

“NIF is a marvel of engineering, but it’s an aging marvel,” NIF Director Gordon Brunton said. “To continue delivering on our missions for the next 20 years, there is a need for more extensive maintenance for obsolete and degraded systems.”

Sustainment activities involve working on parts of NIF that have been untouched since experiments began—like refurbishing the amplifiers in the beamlines and the integrated optics modules (IOM) that sit at the edge of the Target Chamber.

“For our engineering staff, it’s an exciting opportunity to shift from operations to design,” Brunton said. “Sustaining NIF means sustaining our staff too.”

IOM Refurbishment

Samantha Clements was a high school student when NIF was dedicated. Now she’s the project manager for the IOM Refurbishment exchange effort, a key sustainment activity performed during the most recent FM&R in April 2024.

The IOM is an opto-mechanical assembly that houses the final optics assembly (FOA), the final gateway for the laser light before it enters the Target Chamber. It contains the frequency conversion crystals and focusing lenses that allow NIF to precisely deliver record energy to the target.

Nathan Ruiz, IOM and FOA System Manager, left, and Samantha Clements, right, in the NIF Target Bay
Nathan Ruiz, IOM and FOA System Manager, left, and Samantha Clements, right, led planning and execution for the IOM exchange. Eventually all 192 IOMs on NIF beamlines will be exchanged.

While the optics housed in the IOM are exchanged regularly, the IOMs themselves haven’t been touched since they were installed on NIF.

“For the first time ever, we’re going beamline by beamline to remove, inspect, and reinstall each of the 192 IOMs,” Clements said. “We know that over time, the IOMs have experienced wear and tear and that’s led to performance degradation. Now we can directly study that debris contamination and its impact on laser performance.”

This was the second IOM exchange—the first happened in the December 2023 FM&R—and both took about a week. One goal, Clements said, is to improve efficiency so that the remaining IOMs can be exchanged within the next five years. The overall effort involves support from multiple NIF resource teams including operations, alignment, and facility infrastructure, as well as optic and laser scientific and engineering experts who advise this growing workforce generation.

"We’re relearning a process that began nearly 20 years ago,” she said. “And we’ll incorporate what has been learned from operating NIF. Improving processes is important because we want as little downtime as possible, and improvements to NIF operation could ultimately improve laser performance. That’s really the goal, so we can keep pushing boundaries.”

Cryopump Replacement

During the April FM&R, the team also removed and replaced one of NIF’s four cryopumps, which maintain the high vacuum pressure in the Target Chamber.

“One of the cryopumps stopped working several years ago,” said Katya Newman, the cryopump project manager and associate section manager of operations. “We have redundancy, so it hasn’t affected operations, but it puts us at risk if another cryopump goes down. All fusion ignition experiments would cease.”

said Katya Newman, the cryopump project manager and associate section manager of operations.
For Katya Newman, the complexity of the cryopump exchange was exciting.

“It weighs 1,100 pounds, is about the size of a dishwasher, and sits 18 feet off the ground. Pretty much every utility in NIF connects to the cryopump, so that all had to be disconnected. We had to move it 9 feet backward with only 5 inches of clearance. It’s like getting a ship out of a bottle,” she explained.

The cryopump exchange went better than planned, with teams finishing the work more than a day ahead of schedule.

“Our goal is for NIF to produce as much scientific data as possible to support stockpile stewardship and our other missions,” Newman said. “FM&R periods are really impactful times. We keep the facility running and advance what’s possible on NIF.”

The April FM&R ended with success on the cryopump and IOM exchange, along with many other projects. For the facility teams, it was back to business as usual. Planning was already underway for the next FM&R in late summer.

“There is a lot of satisfaction among the entire team at the end of an FM&R,” Sommer said. “When we have discoveries or need to adjust our plan, the team rallies and adapts while continuing to balance safety, security, quality, and efficiency. Everyone has the same motivation, to get the work done and get back to experiments. We work through it, we work together, and we’re always learning. And, at the end, I can reflect on this amazing team and amazing facility.”

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