• tal@kbin.social
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        1 year ago

        I don’t think that that’s necessarily a huge issue, though, because their aim wasn’t to address that.

        That experiment briefly achieved what’s known as fusion ignition by generating 3.15 megajoules of energy output after the laser delivered 2.05 megajoules to the target, the Energy Department said.

        In other words, it produced more energy from fusion than the laser energy used to drive it, the department said.

        A 2020 article, before the current success or the prior one at the same facility:

        https://www.powermag.com/fusion-energy-is-coming-and-maybe-sooner-than-you-think/

        No current device has been able to generate more fusion power than the heating energy required to start the reaction. Scientists measure this assessment with a value known as fusion gain (expressed as the symbol Q), which is the ratio of fusion power to the input power required to maintain the reaction. Q = 1 represents the breakeven point, but because of heat losses, burning plasmas are not reached until about Q = 5. Current tokamaks have achieved around Q = 0.6 with DT reactions. Fusion power plants will need to achieve Q values well above 10 to be economic.

        So if I understand this aright, on the specific thing they’re working on, they’re at 1.54 as of OP’s article, that is (3.15/2.05), up from 0.6 in 2020. The target is somewhere “well above 10” for a commercially-viable fusion power plant. Still other problems to solve, but for the specific thing they’re working on, that maybe gives some idea of where they are.

        • yanyuan@lemmy.world
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          1 year ago

          To my understanding, here they use lasers to create fusion and the 2 megajoules are emitted by the lasers.
          Hence they need waaay more power than is generated to drive their lasers.

          That is also why this research is not actually aiming at power geration, but at fusion weapons. However, the power framing creates much better press and thus better chances for future funding.

          • tal@kbin.social
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            1 year ago

            To my understanding, here they use lasers to create fusion and the 2 megajoules are emitted by the lasers.

            Yes.

            Hence they need waaay more power than is generated to drive their lasers.

            googles

            It sounds like the additional power is due to energy exiting the system:

            https://en.wikipedia.org/wiki/Fusion_energy_gain_factor

            Most fusion reactions release at least some of their energy in a form that cannot be captured within the plasma, so a system at Q = 1 will cool without external heating. With typical fuels, self-heating in fusion reactors is not expected to match the external sources until at least Q ≈ 5. If Q increases past this point, increasing self-heating eventually removes the need for external heating. At this point the reaction becomes self-sustaining, a condition called ignition, and is generally regarded as highly desirable for practical reactor designs. Ignition corresponds to infinite Q.

            So it sounds like additional power requirements effectively means getting from their current 1.54 to 5.

            That is also why this research is not actually aiming at power geration, but at fusion weapons.

            I am confident that that is not the case. The US knows how to do fusion weapons and has for decades – that’s what a thermonuclear bomb is, the second stage. That’s a much simpler problem than fusion power generation. You don’t involve lasers or magnets or other things that you use in fusion power generation if you just want a fusion weapon; you only need to force the material together with a great deal of force for a very brief period of time, and then you’re done.

            • yanyuan@lemmy.world
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              1 year ago

              Yes, the US has fusion weapons since the 50s, but Los Alamos still does research on improvements, maintenance, reliance…

              The US Department of State on the matter:

              Our laser pulls over 300 megajoules off the grid to do these experiments and then converts that into 2 megajoules of laser light and that gave us 3 megajoules of fusion energy.

              And here’s a DOE press release from 2022:

              This historic, first-of-its kind achievement will provide unprecedented capability to support NNSA’s Stockpile Stewardship Program and will provide invaluable insights into the prospects of clean fusion energy…

              That’s why I’m also proud to announce today that I’ve helped to secure the highest ever authorization of over $624 million this year in the National Defense Authorization Act for the ICF program to build on this amazing breakthrough.

    • some_guy@lemmy.sdf.org
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      1 year ago

      Here’s a handy trick that I use on sites such as this one. Between when the article loads and the paywall restricts it, hit a button to display the article in a Reader mode. Safari has this. I believe Firefox does. I think you can get extensions to add such a feature.

      When the article loads and then gets paywalled, this works. When the paywall is immediate it doesn’t.