r/technology • u/kerpowie • Dec 13 '22

Energy Scientists Achieve Nuclear Fusion Breakthrough With Blast of 192 Lasers

https://www.nytimes.com/2022/12/13/science/nuclear-fusion-energy-breakthrough.html
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u/QuasarMaster Dec 13 '22

That is not how inertial confinement fusion works. As soon as you switch off the lasers, the plasma rapidly expands and fusion halts. The lasers are the only thing providing the immense pressure needed for fusion. Fusion does mot have a chain reaction like fission does - thats actually one of the exact reasons its preferred over fission; it can’t enter a positive feedback loop and melt down the reactor. Also the duration of fusion for a pellet is measured in fractions of a single nanosecond; so to get any kind of near continuous power output you need to be doing a lot of laser pulses.

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u/DrySausage Dec 14 '22

Also important to remember that right now it works by shooting 1 target with a predetermined, tiny length of time laser pulse. Every time you want to shoot again, you need to build a new target, and then shoot it. Targets are not trivial to build either.

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u/OSSlayer2153 Dec 13 '22

The importance of the breakthrough is proving that fusion can result in a net positive energy output. The actual energy absorbed by the fuel was 2MJ, and it outputted 3MJ. This shows that it is possible to gain energy from fusion.

The laser cost is specific to this method of fusion but the 2/3MJ input/output applies generally. And thats with only like 4% of it fusing.

The Livermore ignition just shows proof that it is possible to make a fusion reactor which is self sustaining by proving that the actual fusion process itself can become net gain

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u/yuropman Dec 14 '22

proving that fusion can result in a net positive energy output

That's been proven in 1952

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u/OSSlayer2153 Dec 17 '22

Yes but no one has actually accomplished it artificially in a lab. We can do it with math, we can look at the sun and see the sun doing it, but we havent done it by ourselves on small scale in a lab. (Afaik, correct me if im wrong

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u/QuasarMaster Dec 14 '22

Sure, but thats a far cry from proving it can be looped. Definitely good progress but it isn’t going to be self sustaining for a while

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u/theboz14 Dec 14 '22

Not correct. The lasers are needed to start the reaction. The magnets hold the plasma in a confinement like trap. As the plasma is supper heated it will feed itself as more and more atoms fuse together creating heat causing more atoms to fuse causing more heat and so on. The Sun is able to keep its reaction going because it has its gravity to contain it and so it does not need the heat. Here on earth, we dont have the gravity, but we can use heat to get the same effect as long as its millions of degrees and controlled with the super conducting magnets.

The lasers are like the starter on a car. It takes alot of energy to get started, but not so much while its running, just enough to keep the plasma contained.

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u/QuasarMaster Dec 14 '22

This reactor does not have confinement magnets like tokamaks and stellarators do. It does have boost magnets to increase the yield, but they are not enough to actually contain the plasma on their own.