NUCLEAR WEAPONSIgnition Experiment Advances Nuclear Stockpile Stewardship Mission

Published 16 March 2023

When scientists at Lawrence Livermore National Laboratory (LLNL) achieved fusion ignition at the National Ignition Facility (NIF) on Dec. 5, 2022 — an extraordinary scientific breakthrough that was decades in the making — the primary mission and driving goal behind the experiment that day was stockpile stewardship science.

When scientists at Lawrence Livermore National Laboratory (LLNL) achieved fusion ignition at the National Ignition Facility (NIF) on Dec. 5, 2022 — an extraordinary scientific breakthrough that was decades in the making — the primary mission and driving goal behind the experiment that day was stockpile stewardship science.

LLNL is one of two National Nuclear Security Administration (NNSA) laboratories that certify the safety, security and effectiveness of the nuclear explosives packages in the U.S. nuclear stockpile. As part of that work, the Weapon Survivability program develops the innovative computational capabilities and experimental platforms to design and certify the nation’s nuclear deterrent to survive and still perform as expected in a variety of extreme environments, including hostile radiation effects or a nearby nuclear detonation.

“A big part of our science-based Stockpile Stewardship Program is making sure we have experimental access to methods for weapons testing that allow us to test our calculations, check our simulations, develop our intuition, and test the understanding we have from the nuclear tests we did during the underground testing era,” said Mark Herrmann, program director for Weapon Physics and Design at LLNL.

Igniting inertial confinement fusion capsules at NIF simulates aspects of the conditions that exist in an exploding nuclear weapon — producing intense radiation and providing a unique ability for LLNL to test in a pulsed thermonuclear neutron environment.

Commissioning New Fielding Hardware
“The inertial confinement fusion (ICF) program has been working for many years to demonstrate higher megajoule yields and ultimately reach ignition. But that’s not the end in and of itself,” said Laura Berzak Hopkins, associate program director for Integrated Weapon Science. “The goal of the December shot was really two-fold. Not only did we achieve ignition, which is really a remarkable achievement, but we also commissioned a new set of fielding hardware engineered to survive megajoule environments.”

Designed and built by the NIF Materials and Radiation Effects group, the u-shaped hardware, called the cryogenic-compatible X-ray, neutron, and blast snout (CryoXNBS), was inserted into the NIF main target chamber and situated approximately 10 to 12 centimeters from the target, allowing researchers to expose various weapon-relevant samples, such as uranium or other materials, as well as electronics, to the highest possible thermonuclear fusion neutron fluences available.