So the primary purpose of the facility is really for simulating the conditions in those bombs and understanding the physics there. Given that we are no longer testing them, we have to make sure that they’re safe and that we understand how they work. It’s around how we maintain and keep track of our arsenal of hydrogen bombs. The primary purpose of the National Ignition Facility is not actually renewable energy it’s around stockpile stewardship. The hopes that this will somehow be relevant for the human energy supply on Earth are still a really long way off. It’s an amazing piece of physics, and it shows that, as a community, our understanding of the physics of fusion is sufficiently advanced that we can predict and achieve these reactions under the controlled conditions of the National Ignition Facility. GAZETTE: But this is still an overwhelmingly positive development, correct?ĬOHEN: It’s a great one.
There is some amount of radioactive waste produced. On the other hand, the neutrons that come out of a fusion reaction can react with materials they hit to produce low-level residual radioactivity. If you take away the drive, if you take away the lasers, the whole thing stops. You really have to squeeze them very, very hard at high pressures and get them moving really fast at high temperatures in order for there to be any chance of fusion starting. And so it’s very hard to get those nuclei close enough together that the attractive interactions can take over, and that they can actually undergo this reaction. Fusion is very hard to get going: the atomic nuclei of the hydrogen isotopes are positively charged, and we know that like charges repel each other. If you get enough radioactive material together in one place, it will spontaneously undergo fission and you can get runaway reactions. Unlike nuclear fission, fusion is hard to do. GAZETTE: Aren’t there dangers involved in this kind of experiment?ĬOHEN: The experiment itself is not really dangerous. The hope is that we can make this reaction happen on a scale which is controllable enough to be useful for people. It’s the basis of the sun, and it’s the basis of thermonuclear weapons - hydrogen bombs. And as they smash into each other, they release a lot of energy.ĬOHEN: It’s a slightly different reaction in the sun, but that’s also a fusion reaction. They attract each other, just the way the north and south pole of a magnet might attract each other. And when the hydrogen isotopes fuse to make that helium nucleus in the process of them sticking to each other, that releases a lot of energy. They stick to each other very hard, very strongly. Another way of thinking about it is that helium has two protons and two neutrons, and those protons and neutrons are bound to each other. GAZETTE: Why doesn’t it just stay as mass? Why aren’t there just extra bits of mass flying around?ĬOHEN: Mass comes in discrete chunks, and if you add up the mass of a helium and the neutron that comes flying out too in this process, there’s a little bit of a difference. So a little bit of the mass of the hydrogen isotopes that are getting fused together goes into energy, which comes out of this reaction. But how does that create energy?ĬOHEN: Einstein taught us more than a century ago, in his famous formula e = mc2, that you can convert mass into energy. GAZETTE: It sounds like what the scientists did was smash two hydrogen isotopes together to make helium, which has slightly less mass. This process can release huge amounts of energy as the nuclei combine. CohenĬOHEN: Fusion is the process of colliding light nuclei with each other to form heavier nuclei. The interview has been edited for clarity and length. Cohen, a professor of chemistry, chemical biology, and physics, to explain what happened and why it matters.
That is, by focusing 192 giant lasers on a bit of frozen deuterium and tritium, the lab’s National Ignition Facility created a reaction that produced more energy than it used, a threshold called “ignition.” The long-sought result is a major breakthrough in nuclear fusion, with exciting, if still very far off, implications for renewable energy. Department of Energy reported on Thursday.
The Lawrence Livermore National Lab in California last week achieved fusion with a net energy gain, the U.S.
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