Lawrence Livermore Marks Significant Step in Fusion Research
The metallic case (called a hohlraum) which holds the fuel capsule for
NIF experiments. Lasers targeted on the outside of the holraum generate x-rays which bombard the fuel capsule filled
with hydrogen isotopes within. Image courtesy LLNL.
A series of experiments at the National Ignition Facility (NIF) at Lawrence
Livermore National Laboratory (LLNL), a CCST federal laboratory affiliate, have for the first time created a fusion reaction which generated more energy than
was deposited into the fusion fuel, an order of magnitude improvement in yield performance over past
experiments and the first time this result has been achieved anywhere.
"This is a very promising result," said Dr. Peter J. K. (Jeff) Wisoff, acting principal associate director of NIF and Photon Science
at LLNL. "This experimental approach has produced results which align very well
with our computer models; we're still a long way from achieving a positive overall energy yield, but we know where we are on the map."
The NIF facility, which has an annual budget of $329 million, was designed to study the dynamics of nuclear explosions for the National
Nuclear Security Administration and to test the integrity of the country's nuclear stockpile through
simulations rather than exploding weapons. It uses 192 precisely targeted lasers with a peak power
output of 500 trillion watts to heat up a small gold cylinder to millions of degrees. This produces
X-rays which bombard a small spherical plastic shell filled with deuterium and tritium (hydrogen
isotopes), causing some of the atoms to fuse and give off energy.
Because of the indirect means by which the energy of the lasers is transferred to the hydrogen, only a fraction of the
lasers' total output is imparted to the fuel. However, relative to the portion of the energy which was transferred,
the fuel in these experiments gave off as much as 1.7 times more energy than it had taken in.
"We're like the Wright Brothers of fusion power," said Wisoff. "At this point we have basically demonstrated that it can be done.
We're a long way from achieving sustained flight, but we've shown that we can get the air, so to speak."
Although the research agenda at the NIF is driven largely by the needs of the Nuclear Security Administration, the facility
plays an important role in the broader physics research community and works with many researchers around the world. A portion of time with the NIF laser array - the only facility in the world
currently operational with more than a megajoule of energy output - is available for
other research projects, and there is extensive collaboration between NIF and research programs at Sandia, Los Alamos, and
General Atomics, among other institutions.
NIF also works closely with LLNL's High Performance Computing division, which develops increasingly sophisticated computer models
to simulate physical processes which inform NIF's experimental efforts; these, in turn, are used to help refine the computer models.
"At institutions such as Lawrence Livermore, we are
privileged to be able to work on projects with a longer time frame," said Wisoff. "By the Nuclear Safety Administration investing in this research for
national security issues,
we are able to explore questions about fusion reactions in a way that isn't possible in other facilities. We are a part of California's
engine of innovation - eventually the capabilities which we develop will spin
into the private sector. This is the kind of research which is, in the long term, great for California."