Lasers
have usually represented weapons of mass destruction in movies such as
"Star Wars," but a newly completed facility has begun harnessing
lasers to create a fusion reaction rivaling the power of a miniature sun.
The
National Ignition Facility has already test-fired all 192 giant lasers at
Lawrence Livermore National Laboratory in California as part of this effort.
The lasers will eventually focus
their power on compressing and heating a single, pea-sized fuel capsule to
more than 180 million degrees Fahrenheit in order to trigger thermonuclear
fusion.
"One
of the major activities of the NIF is to explore the basics of fusion energy, building
a miniature sun on Earth that could supply limitless, safe and carbon-free
energy," said Ed Moses, National Ignition Facility (NIF) program director.
Unlike
nuclear fission reactions that split apart atoms inside existing power plants,
fusion reactions create energy from atoms fusing together
to form heavier atoms. The reaction normally only takes place within intensely
hot environments, such as the heart of a star, but researchers have attempted
to recreate fusion in a way that would produce more energy than it takes to
start the reaction.
Just
150 micrograms of deuterium and tritium, or less than one-millionth of a pound,
can serve as the fuel for the NIF experiment. But containing the high-temperature
plasma from a fusion reaction represents a special challenge —
temperatures of 180 million degrees F and up would melt any known substance,
apparently including the metallic arms of Spiderman villain 'Doc Ock' in his
fictional fusion experiment from "Spiderman 2."
The
NIF's laser-based approach uses an approach known as inertial confinement
fusion (ICF), which takes advantage of Newton's Third Law about every reaction
having an equal and opposite reaction.
The
rapid, intense heating from the lasers makes the outer layer of the tiny fuel
capsule explode outward, and that compresses the remaining fuel inward and
helps trigger the fusion reaction. Fusion burn consumes the cooler, outer
regions of the capsule faster than the capsule can expand, which contains the
resulting reaction.
This
stands in contrast to previous approaches that have relied on magnetic
fields to contain the plasma from fusion reactions, such as Europe's Joint
European Torus project, although both could work.
"ICF
is analogous to an internal combustion engine where micro-explosions (as in a
car engine cylinder) are continuously occurring to produce energy," Moses
told SPACE.com. "Magnetic fusion is more like a turbine that is
continuously burning fuel to produce energy."
Serious
ignition testing scheduled for 2010 would focus 500 trillion watts of power on
the pea-sized capsule containing deuterium and tritium fuel. NIF has already
produced 25 times more energy than any other existing laser system, and also
became the first fusion laser facility to break the megajoule barrier and create enough energy to power 10,000 100-watt light bulbs for a second.
"We
plan to begin the first experimental shots of the ignition campaign in
May," Moses said.
advertisement
