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| The National Ignition Facility's fusion reactor uses 192 laser beams to focus laser light into a hot-spot the diameter of a human hair. (Image credit: Science History Images/Alamy Stock Photo) |
The breakthrough marks the first time that the core of a fusion reactor has
given out more energy than it has taken in, but significant obstacles still
need to be overcome.
Researchers at U.S. government lab say they have made a "major scientific
breakthrough" in the fiery heart of a nuclear fusion reactor. For the first
time ever, a reactor's core has been detected putting out more energy than
was put into it — a small but consequential step in the race to unleash a
near-limitless, zero-carbon alternate energy source to fossil fuels or
conventional nuclear power plants.
By firing the world's most energetic laser beam to turn the hydrogen
isotopes deuterium and tritium into a burning plasma, physicists at the U.S.
government-funded National Ignition Facility (NIF) at Lawrence Livermore
National Laboratory in California used the lasers' roughly 2 megajoules of
energy to produce around 3 megajoules in the plasma, a 1.5-fold
increase.
Scientists have been trying to build practical methods of harnessing nuclear
fusion — the process that makes stars like our sun burn — ever since the
1940s. By fusing hydrogen atoms to make helium under extremely high
pressures and temperatures, main-sequence stars convert matter into light
and heat, generating enormous amounts of energy without producing greenhouse
gases or long-lasting radioactive waste.
But replicating the conditions found inside the hearts of stars is no simple
task. Besides recreating the hellish temperatures and pressures, vast
quantities of energy are needed to transform fuel into a plasma, ignite it,
and safely corral it with powerful magnetic fields or laser beams. It has
taken decades and many billions of dollars to get here, but ignition has
finally been achieved.
"During experiments 192 high-energy lasers converge on a target about the
size of a peppercorn, heating the capsule of deuterium and tritium to over 3
million degrees Celsius [5.4 million degrees Fahrenheit] and, briefly
simulating the conditions of a star." Jill Hruby, the undersecretary for
Nuclear Security of the U.S. Department of Energy and administrator of the
National Nuclear Security Administration (NNSA), said at a Dec 13. news
conference. "We have taken the first tentative steps towards a clean energy
source that could revolutionize the world."
The experiment, which took place in less than ten billionths of a second,
streamed photons (light particles) into two ends of a cylinder inside the
reactor's core to strike the inner walls of a capsule, producing X-rays
which heated a pellet of fuel into a burning plasma. Once hot, the plasma
burned for an infinitesimal instant, before winking out of existence.
"This is a momentous result in this quest, arguably one of the most
important steps forward ever taken. For the first time, we have evidence of
a fusion reaction producing a sizable amount of excess energy," Gianluca
Sarri, a physics professor at Queen's University Belfast who was not
involved in the experiment, told Live Science. "So far, there were questions
and doubts even on the feasibility of a proof-of-principle experiment of
this kind. These have now been dissipated, injecting so much optimism and
energy to push this forward and solve the technical issues still remaining."
The announcement, initially teased in a
Financial Times article
on Sunday (Dec. 11), generated a flurry of breathless news coverage
excitedly heralding the dawn of unlimited, clean energy. Scientists have
cautioned, however, that this is just the first small step to achieving
fusion commercial power — while a net energy gain was observed between the
lasers and the plasma at the reactor's heart, vastly more energy was
expended than given out across the entire reactor, and fusion faces many
challenges before it can scale up to power our homes.
"It is still not around the corner, unfortunately," Sarri said. "But this
result will undoubtedly speed up developments, both from public institutions
and private companies. Take it with a pinch of salt, but I would dare to say
that we are now talking of a few decades at most before we have a working
nuclear reactor based on fusion."
Source: Link
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Physics