REGIONAL — Researchers at Lawrence Livermore National Laboratory (LLNL) report a major advance in the long and sometimes frustrating effort to generate copious fusion energy by compressing and heating targets with beams from its huge laser, the National Ignition Facility (NIF).
On Aug. 8, they fired NIF beams into a small, intricately designed target containing fusion fuel, which exploded with the highest release of energy thus far achieved on NIF. The burst released 1.35 million joules of energy, eight times the previous record and over two-thirds the energy of the laser light delivered to the target.
Program leaders believe they are now at the threshold of demonstrating “ignition,” which occurs when a “hot spot” of self-sustaining thermonuclear reactions generate a dramatic increase in energy.
The achievement would be signaled by the production of more fusion energy than the laser delivered to the target, a milestone suggested by the National Academies of Science in 1997.
To Mark Herrmann, LLNL deputy program director for fundamental weapons physics, the Aug. 8 experiment was “super exciting,” both for the drama of its immediate result and for the prospect of opening future avenues of research to explore more extreme realms of physics.
It’s usual to publish the results of an experiment in a technical journal before announcing them to the news media, but word of the success was spreading so fast that the Laboratory decided to make a public statement to establish an accurate record, Herrmann said.
A few days after the experiment, Laboratory Director Kim Budil sent an email to Laboratory staff describing the effort as “the culmination of more than 60 years of hard work, innovation and ingenuity, and relentless focus.”
The historical reference was to the invention of the laser, first demonstrated in 1960. Budil’s email traced a number of the key technical developments since then, starting with the realization by LLNL physicist (later director) John Nuckolls that laser beams might be used to explode capsules containing fusion fuel.
Budil went on to credit LLNL’s decades of development of increasingly energetic lasers leading to NIF, but also more recent advances in diagnostic systems, target fabrication, computer simulation and theory.
The emphasis on a long history with many contributions was repeated by NIF director Herrmann. Asked about credit to individuals, he said, “Thousands of people over the decades brought this about. It really is a giant team effort, which our Laboratory is great at. It’s a celebration for the whole team.”
NIF is now in maintenance mode, with operations expected to resume next month. In order to plan for continued progress and improvement, the NIF team is analyzing features of the Aug. 8 shot that contributed to success.
The target was one of a series known as Hybrid-E targets that have produced improved fusion yields over the past three years.
At the National Nuclear Security Administration (NNSA), which oversees the efforts of LLNL and the other nuclear weapons laboratories, newly confirmed NNSA administrator Jill Hruby called the experimental results “extraordinary.”
They “advance the science that NNSA depends on to modernize our nuclear weapons and production, as well as open new avenues of research,” she said. Hruby once worked at Sandia's Livermore site, rising through the ranks to lead all of Sandia National Laboratories.
At Los Alamos National Laboratory, whose researchers are among those who use NIF, Director Thomas Mason commented that the achievement suggests “experiments that will check theory and simulation in the high energy density regime more rigorously than ever possible before and will enable fundamental achievements in applied science and engineering.”
From Washington, D.C., Congressman Eric Swalwell called the experiment a “testament to 50 years of dedication and determination on the part of Lawrence Livermore’s amazing scientists and engineers.”
Despite the enthusiasm and last week’s success, the years of effort have been anything but smooth. During construction in the late 1990s, delays and cost overruns embarrassed and angered the Secretary of Energy, Bill Richardson, who had been assured that the project was on schedule and within budget.
After NIF first began operation in 2009, researchers were unable to create the conditions for ignition as implied in the facility’s name and as predicted by computer models.
Some in Congress and the scientific community called for NIF to be shut down, claiming it had failed to meet its primary goal of achieving ignition. Some of the complaints had questionable motives, however, coming from those who had competed with Livermore for the funding that was required to build and operate the huge laser system.
In addition, as LLNL managers emphasized, NIF had great value even without achieving ignition. Often called the centerpiece of the Stockpile Stewardship Program, it was the nation’s preeminent facility for carrying out research under conditions that approach those of an exploding thermonuclear weapon.
Today, every one of America’s nuclear weapons has been in service beyond its designed lifetime, and studies using NIF’s improved capabilities are likely to be in demand from the scientists and engineers who are responsible for certifying that these aging weapons systems remain reliable and safe.
As Budil said, the Aug. 8 experiment looks like “the first step into a very bright future and a moment of enormous pride for the entire Laboratory.”