NIF hits a record 8.6 MJ of fusion energy at a target gain of 4.13

April 2025 — On April 7, 2025, the National Ignition Facility produced a record 8.6 megajoules of fusion energy from 2.08 megajoules of laser energy delivered to the target, a record target gain of 4.13. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of Oct. 29, 2026 (pages accessed))

Outcome: 8.6 MJ of fusion yield, beating the previous record of 5.2 MJ set in February 2024. (LLNL annual report)
Gain: 4.13, measured against laser energy delivered to the target, not the facility's total power draw. (LLNL annual report; LLNL)
Laser pulse: 2.08 MJ at 456 terawatts peak power. (LLNL annual report)
Cost: not stated by LLNL.
Status: an experiment. LLNL lowered NIF's maximum shot energy from 2.2 MJ to 1.9 MJ while it refurbishes worn optics. (LLNL annual report)

What made the difference

LLNL credits "the combined effects of a higher quality target and improved laser delivery." The April shot retested an improved target design that had produced 5 MJ and a gain of 2.4. (LLNL annual report)

The key was "continuous gradient doping," adding a small amount of tungsten gradually to the thin layers of synthetic diamond in the fuel capsule. Engineer Sean Hayes said the tungsten concentration ramps from zero to about 0.44 atomic percent over 10 microns, then back down, avoiding abrupt changes in density. (LLNL)

"It's the difference between having an off/on light switch and a dimmer switch," said Sal Baxamusa, deputy program manager for target fabrication. (LLNL)

Physicist Dan Clark, lead designer of the experiments, said the main benefit is less "mix," contamination of the fuel by capsule material. "You get higher compression, you get cleaner fuel, and everything burns hotter and brighter." The April shot was only the second ignition experiment to use such a target. (LLNL)

Ignition, repeated

LLNL says it has achieved ignition nine more times since the first on Dec. 5, 2022. The April 2025 shot was the eighth time it achieved ignition. Clark called the step from 3.88 MJ on July 30, 2023 to 8.6 MJ "one of the big jumps in yield in the last few years." LLNL defines ignition as producing more fusion energy than the laser energy delivered to the target. (LLNL)

The capsules are grown over several days by plasma-assisted chemical vapor deposition around a silicon carbide core, and LLNL says partners produced the exact dopant profile on the first attempt. (LLNL)

What the shots are for

"This record result, enabled in part by a major innovation in target design, has sent a clear signal that the U.S. is expanding the frontier of fusion science and technology," said Vincent Tang, who leads LLNL's NIF and Photon Science Directorate. (LLNL)

LLNL frames ignition mainly as support for the National Nuclear Security Administration's stockpile work. Ignition shots supply neutrons to test whether weapons components would survive hostile conditions; an Oct. 1, 2025 shot that yielded 3.6 MJ exposed weapons-grade plutonium samples. (LLNL annual report)

LLNL says record gains "also provide a physics basis" for fusion as baseload power. (LLNL)

Wear and tear

NIF's 192 integrated optics modules have worn over 20 years, and LLNL found a source of debris affecting 32 upper inner beamlines. A fast-track refurbishment is due to finish in fiscal 2026; until then the maximum shot energy has been lowered as a precaution. (LLNL annual report)

What went wrong

Gain isn't net power. The 4.13 compares fusion output with laser energy on target. LLNL's pages don't give the electricity the lasers draw. (LLNL)
The facility is aging. Debris from worn optics modules led LLNL to cut the maximum shot energy from 2.2 MJ to 1.9 MJ. (LLNL annual report)
Weapons work leads. LLNL lists supporting stockpile modernization first among NIF's missions, and calls ignition 'a key element' of its support for the NNSA. (LLNL annual report; LLNL)
What we don't know yet: the cost per shot, and whether the record has been raised since.

Our follow-up question for Lawrence Livermore National Laboratory

Has NIF restored its 2.2 MJ maximum shot energy, and has any shot since beaten 8.6 MJ?

Sources

Lawrence Livermore National Laboratory, “National Ignition Facility,” FY 2025 annual report, accessed Oct. 29, 2026. annual.llnl.gov
Lawrence Livermore National Laboratory, “Target Breakthrough Enabled Fusion Record at NIF,” April 15, 2026. lasers.llnl.gov

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