[LINK] Nuclear fusion

[stephen at melbpc.org.au]

Can world's largest laser zap Earth's energy woes?

By John D. Sutter, CNN April 28, 2010 -- Updated 1805 GMT (0205 HKT)
http://edition.cnn.com/2010/TECH/science/04/28/laser.fusion.nif/index.html


Livermore, California (CNN) -- Scientists at a government lab here are 
trying to use the world's largest laser -- it's the size of three 
football fields -- to set off a nuclear reaction so intense that it will 
make a star bloom on the surface of the Earth.

The Lawrence Livermore National Laboratory's ambitious experiment will be 
tried for real, and for the first time, late this summer.

If they're successful, the scientists hope to solve the global energy 
crisis by harnessing the energy generated by the mini-star.

Researchers in Livermore, about an hour's drive east of San Francisco, 
say it's not a matter of if but when their laser-saves-the-Earth 
experiment will be proved successful.

"We have a very high confidence that we will be able to ignite the target 
within the next two years," thus proving that controlled fusion is 
possible, said Bruno Van Wonterghem, a manager of the project, which is 
called the National Ignition Facility.

That would put the lab a step closer to "our big dream," he said, which 
is "to solve the energy problems of the world."

How to build a star

Here is the boiled-down recipe for how the Livermore lab plans to cook up 
a star:

Step one: Build the largest laser in the world, preferably inside a drab-
looking office building. (To do this, you'll have to suspend all previous 
notions about what a laser looks like. This one is basically a giant 
factory full of tubes. The laser beam, which is concentrated light, 
bounces back and forth over the distance of a mile, charging up as it 
goes.)

Step two: Split this humongous laser into 192 beams. Aim all of them -- 
firing-range style -- at a single point that's about the size of a BB.

Step three: On that tiny target, apply a smidge of deuterium and tritium, 
two reactive isotopes of hydrogen that can be extracted from seawater. 
Surround those atoms with a gold capsule that's smaller than a thimble.

Step four: Fire the laser!

If all goes well, the resulting reaction will be hotter than the center 
of the sun (more than 100 million degrees Celsius) and will exert more 
pressure than 100 billion atmospheres. This will smash the hydrogen 
isotopes together with so much force and heat that their nuclei will 
fuse, sending off energy and neutrons.

Voila. An itty-bitty star is born.

Miracle cure?

The fusion reaction at the heart of this recipe is the same one that 
fuels the sun in our solar system and other stars.

"It's the most fundamental energy source in nature," Van Wonterghem said.

Workers at the Livermore Lab insist that the reaction isn't dangerous. 
Their version of fusion is controlled, rather than explosive like in 
America's current arsenal of nuclear weapons, which include a fusion 
reaction.

"There's no danger to the public," said Lynda Seaver, spokeswoman for the 
project.

"The [worst possible] mishap is, it doesn't work."

The fusion reaction does emit radioactive neutrons. But to stop those 
neutrons from escaping, the Livermore lab surrounds the reaction chamber 
with concrete walls that are more than 6½ feet thick.

Despite the fact that the reaction will "even exceed the conditions at 
the center of the sun," Van Wonterghem said, the controlled fusion is 
expected to be incredibly small and short-lived.

The star being cooked up in Livermore this summer is expected to die 200 
trillionths of a second after it's ignited, Van Wonterghem said. 

And it will measure only 5 microns across, which is several times smaller 
than the width of a human hair.

Road to commercialization

The value of this summer's experiment in laser-induced fusion will be in 
proving that powerful beams of light can produce a controlled fusion 
reaction, Seaver said.

It will take at least another 20 years, with adequate funding, to develop 
a continuous fusion reaction that could heat water, create steam and turn 
generators at a commercial fusion power plant, she said.

Meanwhile, the project is behind schedule and over budget, according to 
government reports.

Since 2005, when the laser-fusion experiment was isolated in a government 
program called the National Ignition Campaign, the project has spent more 
than $2 billion, or 25 percent more than its budget of $1.6 billion, 
according to the April Government Accountability Office report.

And, in those recent years, the project has fallen a year off schedule, 
the GAO says, with the expected completion date for the research now at 
the end of 2012.

Seaver, the National Ignition Facility spokeswoman, said the report 
mischaracterizes the lab's work.

"NIF has held all its milestones. It's held to its budget. The 
experiments are going just fine at NIF," she said. "They're going the way 
we thought they would."

Construction on the Livermore laser facility began in 1997, but the laser 
technology needed for the experiment has been 50 years in development, 
she said.

Meanwhile, other labs are working on fusion projects, too.

ITER, a project in France, for example, aims to use magnets and plasma, 
instead of lasers, to test nuclear fusion.

Research continues in non-fusion areas of nuclear power, as well.

Microsoft founder Bill Gates announced in February that he is funding 
research in a modified and more sustainable version of nuclear fission, 
the type of reaction that powers the world's existing nuclear reactors.

Fission involves splitting large, heavy atoms. Fusion, the star-making 
reaction being tried in Livermore, works the opposite way, sealing the 
nuclei of smaller atoms together.

The Livermore lab says it could get its fuel -- the two isotopes of 
hydrogen -- from seawater.

The process for extracting large amounts of deuterium and tritium from 
water has not been perfected, but the lab says the supply of these 
materials is nearly limitless.

"One gallon of seawater would provide the equivalent energy of 300 
gallons of gasoline; fuel from 50 cups of water contains the energy 
equivalent of two tons of coal," the Livermore project's website says.

Unlike burning coal and natural gas, nuclear power does not produce 
greenhouse gases.

Doubts and optimism

Critics of Livermore's fusion research say it's too expensive and too 
theoretical.

The world needs to employ existing fixes for climate change rather than 
looking for a technological silver bullet that will prove to be too 
expensive for commercial energy production anyway, said Thomas B. 
Cochran, a senior scientist and nuclear physicist at the Natural 
Resources Defense Council, an environmental group.

"If you want to do [research and development] to alleviate climate 
change, you have to have technologies that can be brought online soon," 
he said. "We don't have much time to turn this around."

Even if the facility's lasers do create a fusion reaction, the lab is 
still a long way from becoming a commercial power plant, he said. 

"It's not going to be competitive," he said. "It's crazy to go down that 
road. It's kind of fun and interesting -- graduate student projects 
designing these concepts. But they waste a lot of money in thinking 
[nuclear fusion] is going to contribute to society."

Nevertheless, the scientists in Livermore remain optimistic.

Van Wonterghem holds out hope for an energy miracle from fusion and has 
invested his entire career in the idea. Seaver believes that what's 
happening at the lab is historic.

"This is something you're going to tell your grandchildren about," the 
spokeswoman said on a recent tour of the lab. "You were here when they 
were about to get fusion ignition.

"It's like standing on the hill watching the Wright brothers' plane go 
by."

--

Cheers,
Stephen