Optics and Photonics

Fusion: On the Threshold of Ignition

On August 8, 2021, LLNL achieved a significant milestone in fusion research, demonstrating a fusion yield of 1.35 megajoules on NIF, more than two-thirds of the 1.9 megajoules of laser energy going in. Fusion is the process that powers the sun and occurs when the nuclei of light atoms such as hydrogen overcome the repulsive electrostatic force that keeps them apart, and “fuse” to form a heavier nucleus and large amounts of energy released in the form of alpha particles, high-energy neutrons, and electromagnetic radiation.

The experiment in August 2021 was enabled by focusing laser light from the 192 beams of NIF — the world’s largest and most energetic laser — onto a highly engineered target the size of a BB that contains the fusion fuel. The result is a hot spot the diameter of a human hair that creates conditions hotter and denser than those found at the center of the sun. The 2021 result placed NIF on the threshold of fusion ignition (defined as more energy out of the target than went in with the laser) for the first time. Target fabrication, diagnostics, laser performance, controls and operation all came together to create this breakthrough result.

NIF's central mission is to provide experimental insight and data for the National Nuclear Security Administration’s science-based Stockpile Stewardship Program. Experiments in pursuit of fusion ignition are a vital part of this effort. They provide data in an important experimental regime that is extremely difficult to access, furthering our understanding of the fundamental processes of fusion ignition and burn, and enhancing the simulation tools that support our stockpile stewardship mission. Fusion ignition is the gateway toward even higher fusion yields in the future.

Achieving fusion ignition is also the first major hurdle in efficiently harvesting fusion energy, a clean and potentially limitless energy source.

Vera C. Rubin Telescope

In September 2021, LLNL engineers completed delivery of six optical components for a telescope expected to observe 20 billion galaxies from the Rubin Observatory in Chile. The project has been underway for about 10 years and involves industrial partners who did much of the fabrication. It is anticipated that the resulting Legacy Survey of Space and Time Camera (LSSTCam), will start imaging the southern sky in 2024.

A key feature of the LSSTCam’s optical assemblies will be its three lenses, one of which is the world’s largest high-performance optical lens ever fabricated, at 5.1 feet (1.57 meters) in diameter. The 8.4-meter telescope at Rubin Observatory will take digital images of the entire visible southern sky every few nights, revealing unprecedented details of the universe and helping unravel some of its greatest mysteries. During a 10-year time frame that will detect about 20 billion galaxies, the telescope will create a time-lapse "movie" of the sky.

This data will help researchers better understand dark matter and dark energy, which together make up 95 percent of the universe, but whose makeup remains unknown, as well as study the formation of galaxies, track potentially hazardous asteroids and observe exploding stars. The telescope’s camera will capture full-sky images at such high resolution that it would take 1,500 high-definition television screens to display just one picture.