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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

#181

Post by woeirua »

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,…

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."

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

#182

Post by woeirua »

px43 wrote: post #164
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…

With the Higgs, we got the mass, which was not predicted by any of the theoretical models. We were basically done at that point. With LIGO we got tons of tangible data of black holes colliding. Fusion is not useful until Q>1, and for NIF to claim that when it obviously isn't true is, IMO, a bad look. They invented Qplasma where they arbitrarily get to ignore over 99% of the energy that actually went in, and don't nee…

Why even have any press conferences then until we have a working commercial reactor? Come on, this is just ridiculous.

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

#183

Post by woeirua »

walnutclosefarm wrote: post #157
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.

Exactly. If there was a breakthrough at all, it in 2021, when NIF finally reached the point of "burning plasma." But breakthrough, or milestone, I fear it may all be for naught. The improvements over the last two years are essentially all due to changes in the hohlraum geometry and preparation. All good, if your goal is to get burning plasmas to study. But NIF is orders of magnitude away from anything useful for powe…

The design of NIF was never intended to be viable for commercial power generation.

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

#184

Post by photochemsyn »

This article is obviously a PR piece, not an objective review, and the interviewee receives funding from the program. Looking around a bit, here's a discussion from 2018 that's a bit more revealing:

https://physicstoday.scitation.org/do/10.1063/pt.6.2.2018061...

> "In the latest round of experiments, the capsule shells consisted of diamond doped with a thin layer of tungsten, and the hohlraums were made of depleted uranium. Earlier experiments had used plastic shells and gold hohlraums. Sebastien Le Pape, lead author of the paper, says the uranium hohlraum boosted the peak energy deposited on the capsule by 25 terawatts, for a total of about 450 TW."

Clearly the cost of these fuel capsules is prohibitive when it comes to any practical power production system, plus there's nothing like an energy capture-and-conversion-to-electricity system being developed. It certainly looks more like nuclear weapons research than power production research. The real goal is just preserving the budgetary outlay:

> "The new results were achieved before the Trump administration proposed cutting funding for NIF by $57 million, to $287 million in fiscal year 2019. That would have forced a 30% reduction in the number of experimental shots of the 192-beam laser. Lawmakers instead added to NIF’s funding next year: The final appropriation will likely end up between the $330 million included in a House-passed bill and $344 million included in a Senate measure."

Notably, DOE budgets for solar PV development remain entirely minuscule in comparison, which is one reason why it's China, not the USA, that has mastered efficient production of high-efficiency, high-durability monocrystalline silicon PV panels at scale. These of course compete directly with natural gas for power production, and the US wants to be the biggest natural gas exporter in the world. Not hard to understand what's really going on at the DOE/NNSA, whose original name was the Manhattan Project, then the AEC:

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

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

#185

Post by walnutclosefarm »

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…

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 absorbed in one part of the burn, from the NIF lasers, to that released in another, from 0.7, which they had achieved in August of 2021, to 1.5. That's it. That, and the fact that it's funding season in Washington, so not a bad time blow NIF's horn.

Milestone, yes. You have to get Q above one if you're starting at .01, and need to get to 100 and 1 is a great mile marker. But, But breakhrough - I don't think so.

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

#186

Post by slothtrop »

hilbert42 wrote: post #172
sigmoid10 wrote: post #86

Earlier quoted context omitted.

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..." Yes, I'd agree with that statement that it's only an engineering problem, but with a laser energy of 2 million joules and a fusion yield of only 3 million joules and an overall input of nearly 300 million joules to produce the lasers then I've no expectation of ever seeing a total net positive output in my lif…

Do we care about performance when the purpose is proof-of-concept? Those numbers aren't set in stone. Efficiency won't be utilized when it's besides the point.

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

#187

Post by tmikaeld »

danbruc wrote: post #91
TheOtherHobbes wrote: post #76

Earlier quoted context omitted.

I'm not sure if it's theoretically impossible. But it's certainly an incredible challenge to build a high efficiency laser system that can consistently generate many pulses per second without degrading either the laser head itself or any associated micro-focussing optics. Can we stop pretending this isn't about nuclear weapons research and - basically - continued funding? LLNL is at least a decade behind its initial…

My point was purely about the claimed impossibility of a hundredfold efficiency increase which is only true if you are already about 1 % efficient. I have no real opinion on what the NIF is doing or not, at best my layman judgment would be that laser fusion is way further from becoming practical than tokamaks or stellerators.

You're right that we don't have enough information here, I've been reading a lot about it's theory and practicality throughout the years. There's also theories about ignition in parallell, by using multiple pellets. Since the first step has been taken, there's a lot of avenues for improvement. However, one also has to take into account the "chaos" created by the ignition in the first place, re-introducing an additional pellet or chain reaction has it's own challenges.

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

#188

Post by pfdietz »

Robotbeat wrote: post #173
rz2k wrote: post #155

Earlier quoted context omitted.

And that graph does not include the 2022 experiment with 3.15, which also happened to be the first one with net positive output.

Yup, here’s the one: https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Credit: Mark Herrmann/LLNL From this article: https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Clear qualitative difference. Additionally, this is laser energy, but the lasers aren’t used directly. They produce X-rays which are the ones that actually drive the ablative implosion of the fuel pellet. If you used X-rays d…

It should be noted that even if the lasers were 100% efficient, this result is not sufficient to achieve a practical fusion power plant. That target could produce maybe $0.02 worth of electrical energy. That's nowhere close to paying for the plant, even totally ignoring operating costs.

A real plant would need target yields 100 to 1000 times larger, with all the engineering issues that would entail.

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

#189

Post by throwawaymaths »

thereddaikon wrote: post #167
px43 wrote: post #164

Earlier quoted context omitted.

With the Higgs, we got the mass, which was not predicted by any of the theoretical models. We were basically done at that point. With LIGO we got tons of tangible data of black holes colliding. Fusion is not useful until Q>1, and for NIF to claim that when it obviously isn't true is, IMO, a bad look. They invented Qplasma where they arbitrarily get to ignore over 99% of the energy that actually went in, and don't nee…

I'd argue Q>1 isn't worth a press conference either. People care about commercial power generation and that needs more like Q>150.

Depends on the device. Q_plasms > 150 iirc is the estimate for MCF fusion. The NIF lasers take in way more energy than they put into the pellet, so that I think you want something like Q_plasma > 10,000 iirc.

Iirc most engineers use a different Q, which refers to all in energy, so Q > 1.5 ish is enough

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

#190

Post by serioussecurity »

zmgsabst wrote: post #114
HPsquared wrote: post #97

Earlier quoted context omitted.

Parent was basically saying it has not been a physics problem for decades, it's already an engineering problem and there is no change there. The physics are known to work and have been demonstrated decades ago in a different engineering context (i.e. weapons).

We can debate the importance, but it’s clear that they’ve made a qualitative leap in their technology the past few years — a “breakthrough”. https://en.wikipedia.org/wiki/National_Ignition_Facility#/me...

Not to diminish the achievement, but not making that graph log scale was deeply dishonest.
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