Giant Laser in the Works to Achieve Fusion
Article by Shane Ennerson
In the movie “Spiderman II,” the web-slinging hero stops the creation of a tritium-fueled laser fusion machine. Doctor Octopus’s theory was right, but his machine was too small.
Scientists at the Lawrence Livermore National Laboratory in California are building their own laser fusion machine that is 10 stories tall, 400 feet long and fueled with tritium (and deuterium).
The goal of the project, known as the National Ignition Facility (NIF), is to create such intense heat and pressure that the fuel, both isotopes of the element hydrogen, will fuse together to form helium.
Researchers expect that reaction will release massive amounts of energy that could one day provide nearly unlimited and environmentally friendly power to the world, advance basic scientific research and ensure the effectiveness of the nation’s nuclear warheads.
“It is absolutely essential that we try this,” said Richard Petrasso of the Massachusetts Institute of Technology’s Plasma Science and Fusion Center who is also working on the NIF.
“If we can in fact achieve fusion and make copious amounts of energy, that would be a clear achievement.”
To achieve nuclear fusion, scientists will cool samples of deuterium and tritium — two isotopes of the element hydrogen that have extra neutrons — to just above absolute zero in a glass-capped cylinder about the size of a quarter.
Then 192 laser beams, split into two groups, will shine onto the fuel, heating it up to about the point of ignition.
Some of the energy will explode outwards, but some of the energy will further compress the innermost core of the fuel, compressing it so much that two hydrogen atoms will fuse together and create one helium atom.
Nuclear ignition, as Petrasso explains, is like a smoldering log suddenly bursting into flames.
“Once you reach certain conditions of pressure and temperature that log will spontaneously start to burn,” said Petrasso. “But the fuel for NIF is nuclear, not chemical, and because of that we will get much more energy.”
That reaction powers and creates similar, but controlled conditions found in huge supernovae many times the size of the sun and thermonuclear warheads, both of which will also be research focuses at the NIF, said Bob Hirschfeld, also at the NIF.
Since exploding nuclear warheads both above and below ground is now forbidden, the military has a difficult time telling if its stockpile of nuclear weapons works.
For those worried about the prospect of either a supernovae or thermonuclear explosion stemming from the project, Hirschfeld says not to worry.
“The amount of fuel being used is smaller than a BB,” said Hirschfeld. “And the reaction is not self-sustaining,” meaning that without the lasers the reaction will fizzle out harmlessly.
The target chamber is also encased in aluminum, then in 16 inches of concrete, which is then encased with another round of concrete.
The lasers can only fire every few hours because of the extreme heat generated by the 500 trillion watts, more than 1,000 times the power generated in the United States at any moment, necessary to power the lasers.
Despite its size and energy consumption, the goal of cheap energy has attracted other countries to nuclear fusion as well.
Scientists in France and the U.K. are working on other laser-based fusion plans. Other groups, notably the ITER experiment to be based in France, are trying to reach ignition through magnetic fields.
However nuclear fusion is achieved, the result would be a boon for humanity.
“The great thing about fusion is the fuel is widely available to all nations, it’s a relatively benign form of energy, and there isn’t long-lived radioactive waste,” said Ron Davidson of Princeton University who is not involved in the NIF.
“It would be a great scientific step forward if the NIF achieves ignition and I personally believe that they will.”
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Freelance writer working for Dragonlasers at http://www.dragonlasers.com
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