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Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

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Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#241

Post by rini17 »

zardo wrote: post #229
walnutclosefarm wrote: post #185

Earlier quoted context omitted.

Actually, I think the pedanticism is on the part of the people announcing this "breakthrough." The definition of "break even" used here (that is, Q>1) is highly technical, and but one factor in the actual "break even" equation. This experiment didn't prove you could get more energy out of a fusion burn than you put in (which is the notion they want to evoke), but rather that they could raise the ratio of energy absor…

> This experiment didn't prove you could get more energy out of a fusion burn than you put in. Haven't H-bomb tests already proven that beyond all doubt?

I think he meant _useful_ energy. Is it so surprising that HN is primarily interested about civilian applications and cynical when none are in foreseeable future?

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#242

Post by delecti »

zardo wrote: post #229
walnutclosefarm wrote: post #185

Earlier quoted context omitted.

Actually, I think the pedanticism is on the part of the people announcing this "breakthrough." The definition of "break even" used here (that is, Q>1) is highly technical, and but one factor in the actual "break even" equation. This experiment didn't prove you could get more energy out of a fusion burn than you put in (which is the notion they want to evoke), but rather that they could raise the ratio of energy absor…

> This experiment didn't prove you could get more energy out of a fusion burn than you put in. Haven't H-bomb tests already proven that beyond all doubt?

The existence of stars already did. This is more like "it's plausible to do so in a reactor that won't destroy itself". The "that won't destroy itself" part is what this demonstrates, but annoyingly reporting often shortens it to the "is plausible to do so" part.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#243

Post by MarcelOlsz »

dotnet00 wrote: post #120
bawolff wrote: post #39

Everything i have heard about this makes it sound more like a milestone than a breakthrough. I.e. its great it happened and an important step, but its not shocking that we eventually did it. When i hear breakthrough i think of something more unexpected. I.e. figuring out how to solve a problem we had no idea how to solve.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

>I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why.

It reminds us how pointless our Javascript-based existence is.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#244

Post by mikeyouse »

corille wrote: post #239
mikeyouse wrote: post #213

Earlier quoted context omitted.

So the NIF spec'ed out a replacement using a diode-pumped Yb:SFAP laser that they estimated to be 10% efficient in ~2009: https://en.wikipedia.org/wiki/Mercury_laser https://www.laserfocusworld.com/test-measurement/research/ar... The second link has more details, but they show a 0.7% efficient NIF vs. a 7% efficient Mercury laser in the tiny little chart graphic -- which would reduce the energy for this experiment fr…

Thank you for interesting links. However, I see that the specified pulse energy of a single Mercury laser is 100J vs 18.7kJ for NIF so my point is still valid. There is no way to arrange 20k lasers all pointing at one pellet.

That was just a prototype laser to prove the direct drive approach with a high frequency solution.. They demo'ed a suitable laser operating at 10hz vs. 0.0001HZ with the existing NIF capability. Since the 100J Mercury laser was transferring more than 10x the energy to target compared to NIF (with an obvious path to 20x) - think of this as a 1/20th scale replacement for a single NIF beam with the ability to fire multiple shots per second.

Even if they couldn't increase the power past 100J (which they certainly can), using 2,000 beams instead of 192 doesn't seem too difficult given the much smaller overall energy and heat-removal requirements.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#245

Post by Animats »

sigmoid10 wrote: post #86
rob74 wrote: post #43

Still unconvinced why this is such a major breakthrough - it may be the first net-positive controlled fusion, but the distinction between controlled and uncontrolled fusion is a bit academic in this case. In uncontrolled fusion ( https://en.wikipedia.org/wiki/Thermonuclear_weapon ), you are using a nuclear fission primary stage to generate enough energy to start the fusion reaction in the secondary stage. In the NIF,…

You greatly underestimate the order of magnitude difference of produced energy in these two examples. You can't contain a bomb's hydrogen fusion reaction in a chamber for the simple reason that you need a nuclear fission warhead just to ignite it. So if you want to produce useful, controlled energy outside of killing things, the lasers are your only shot for inertial confinement fusion. Yes they still get damaged, bu…

> This news shows that practical fusion is now only an engineering problem, not a fundamental physics one - like it still is for Tokamaks and Stellarotors. For them no one knows if it is even possible to e.g. control turbulence long enough to achieve net positive energy gain.

Well, sort of. This is "theoretical breakeven" - the reaction generated more energy than they put in. "Technical breakeven", where you generate enough power to run the thing, is 2-3 orders of magnitude away. It's not at all clear that pulsed fusion like this is a viable power source even if it reaches technical breakeven.

The magnetic containment people are still struggling, but making progress. For a long time, everybody was looking for some clever magnet geometry that would yield stable plasmas, with limited success. Maybe active control will work. There are now people throwing machine learning at the problem.[1]

[1] https://news.mit.edu/2022/fusion-machine-learning-turbulence...

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#246

Post by nforgerit »

I'm just an interested layman on the sideline watching from "old Europe" but can't help but ask: Is everything okay with your science-media sector over there in the US? Lately, I've been asked to believe this weird wormhole story[0] and now this "major breakthrough" in fusion ignition? This all smells like too much marketing BS to me.

[0] https://www.quantamagazine.org/physicists-create-a-wormhole-...

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#247

Post by floxy »

walnutclosefarm wrote: post #185
dotnet00 wrote: post #120

Earlier quoted context omitted.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

Actually, I think the pedanticism is on the part of the people announcing this "breakthrough." The definition of "break even" used here (that is, Q>1) is highly technical, and but one factor in the actual "break even" equation. This experiment didn't prove you could get more energy out of a fusion burn than you put in (which is the notion they want to evoke), but rather that they could raise the ratio of energy absor…

>The definition of "break even" used here (that is, Q>1) is highly technical, and but one factor in the actual "break even" equation.

Isn't the Qplasma > 1 the most important one here, by a very wide margin? Maybe the only important one at this point in time. That fusion begets more fusion, in a positive-feedback way. That's the breakthrough here. All the other efficiency factors are secondary in nature. That is step 1, and the next step is to scale this up so that eventually Qplasma >> 1. And only then the hand wringing about efficiency of the lasers becomes something to address. It seems like the baby was just born, and people are concerned about which colleges to apply to.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#248

Post by hinkley »

hinkley wrote: post #206
woeirua wrote: post #181

Earlier quoted context omitted.

This comment sums up HN beautifully: "Here's an article from a subject matter expert on this topic, but I'm going to go ahead and ignore everything that was said because it doesn't fit my narrative."

You find us a subject matter expert in building production fusion power plants and we’ll get back to you. What we have are a bunch of R&D people, some of which are using ingredients for which the entire world combined possesses enough fuel to run a single power plant for only two months, and then we’re out.

Too late to edit, but my source on the 2 months comment comes from an interview with Helion, who I think made the front page a couple of weeks ago, but in summary they are trying to smash two plasma balls together and then directly capture the magnetic flux created by the resulting fusion, rather than using a heat engine:

https://youtube.com/watch?v=_bDXXWQxK38&t=1081s

They talk about why ITER has no viable fuel source, and about how they (Helion) are going to have to run two configurations of fusion plants in order to source their own fuel. One that produces a 10% power surplus, undesirable neutrons and the fuel for their power plants. They didn’t say anything but I suspect they’ll end up coming up with a use for the neutrons, perhaps making fuels for other processes. Someone will likely eyeball that waste heat as well.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#249

Post by horsawlarway »

delecti wrote: post #242
zardo wrote: post #229

Earlier quoted context omitted.

> This experiment didn't prove you could get more energy out of a fusion burn than you put in. Haven't H-bomb tests already proven that beyond all doubt?

The existence of stars already did. This is more like "it's plausible to do so in a reactor that won't destroy itself". The "that won't destroy itself" part is what this demonstrates, but annoyingly reporting often shortens it to the "is plausible to do so" part.

Except... correct me if I'm wrong here... The "reactor" did destroy itself.

> The fuel and canister get vaporized within a few billionths of a second during the experiment. Researchers then hope their equipment survived the heat and accurately measured the energy released by the fusion reaction.

It didn't necessarily blow up like a fusion bomb, but the energy was hardly produced in any sort of sustainable, ongoing form that we can harvest.

Worse - it's not even just the chamber that essentially destroys itself - the lasers that create the event also damage themselves: https://lasers.llnl.gov/news/controlling-backscatter-damage-...

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#250

Post by chasil »

denton-scratch wrote: post #80
rgmerk wrote: post #31

Earlier quoted context omitted.

It might guarantee clean fusion power, but there's no guarantee it would be in any way economic. Edward Teller proposed something along these lines with conventional two-stage nuclear explosives back in the 1970s, but it was rapidly abandoned as horribly inefficient and costly: https://en.wikipedia.org/wiki/Project_PACER I know this stuff is fun to speculate about but the boring and unsexy option of more solar panels…

> clean fusion power From what I understand, practical routes to fusion all produce a lot of fast neutrons, and tritium. The neutrons make the surrounding equipment radioactive, and create toxic elements. The tritium is itself toxic, and is hard to contain. And the high neutron flux means that such a machine could easily be used to create weapons-grade plutonium, by irradiating uranium. And come decommissioning time,…

One fusion approach that was recently discussed here was anetronic fusion with Hydrogen and Boron-11.

Because it produces no free neutrons, it doesn't have the (small) waste problem as this laser fusion approach.

This article is newer from the one that I remember.

https://news.ycombinator.com/item?id=30841080

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