Laser fusion facility heads back to drawing board

https://www.nature.com/articles/d41586-022-02022-1

by anigbrowl • 4 years ago

82 104 4 years ago

irjustin• 4 years ago

Of all the ideas surrounding fusion, this one I've always had the most difficult in imagining it working at any level of production.

The kid in me says this was/is the coolest option.

Regardless of outcome, I'm glad we were able to test the idea.

pram• 4 years ago

IIRC it seems impractical because it was intended for nuclear weapons research or something like that. It's a military boondoggle.

RF_Savage• 4 years ago

Yep. It's an alternative to nuclear tests to see how the physics work in real life.

Sometimes it's just nice to have something to compare your simulation results to.

XorNot• 4 years ago

I wouldn't say boondoggle. The need for nuclear deterrent is back in focus, and so long as that exists then I'd much prefer we do anything but actual weapons tests.

hangonhn• 4 years ago

What was the expected long term outcome of the nuclear test ban treaties? It seems unless there is some breakthrough in simulations and NIF type experiments, all countries with nuclear weapons will end up unsure of their weapons efficacy. Is this intentional? Is the hoped for outcome that no one has nuclear weapons they are sure will work and thus effectively disarming them? If not, are facilities like NIF what was envisioned by all the countries who have nuclear weapons?

Thanks.

pjc50• 4 years ago

This is a serious albatross round the neck of nuclear technologies; if they're dual-use, they'll get lots of funding, making them look expensive, while the true purpose and feature set is obscured, making them look nonsensical.

etrautmann• 4 years ago

It does seem like fusion research based on tokamak or stellerator designs will yield usable power first.

kersplody• 4 years ago

And even then, we are decades away from a commercial design due to the large number of engineering challenges needing to be solved. The next major milestone is getting a plasma gain of > 5, where helium-4 interactions become the dominant source of heating and dramatically change the behavior of the plasma. This has been simulated but never experimentally archived. Hopefully ITER will achieve this by 2030. Keep in mind that continuous operation with a Q plasma gain of at least 75 will be required for a commercially viable reactor. ITER will be lucky to hit 15 with upgrades through 2040.

brudgers3• 4 years ago

When I first read that tokamaks were a promising idea, Brezhnev was still alive.

TomMasz• 4 years ago

The University of Rochester's Laboratory for Laser Energetics was working on laser fusion back in the late 70s. Despite multiple upgrades, they never achieved the goal, eventually outgrew the facility and the DoE moved on to the NIF. It really underscores how difficult laser fusion is and how important it must be to merit pouring all that money into.

jinto36• 4 years ago

The LLE at least wasn't a single purpose build-abandon-dismantle project, and still operates for research. https://en.wikipedia.org/wiki/Laboratory_for_Laser_Energetic...

nonrandomstring2• 4 years ago

Reading between the lines it seems the failure to replicate results is down to a lack of precision engineering capability. Is anyone who understands the experiment in detail able to comment?

Sounds like what goes on at the focal point of the laser requires nanometers of accuracy in design, position and orientation. Perhaps part of the problem is that we abandoned physical engineering and manufacture in the west in favour of outsourcing it all?

sandworm1013• 4 years ago

Focal point isn't the problem. It is more about timing, getting all the lasers to hit at the same time.

And no, this has nothing to do with outsourcing. There are no outside experts in this field.

nonrandomstring2• 4 years ago

I see. A similar problem to aligning the detonation wave in the early plutonium bomb designs then, only with the speed of light as a constraint. Tricky.

doctorwho42• 4 years ago

This is a facility that is critical to US stockpile stewardship. None of the tech or engineering or manufacturing has been offshores/outsourced.

The engineering and fabrication side is just that precise.

In this facility they indirectly drive the target with the lasers. So instead of uniformly heating a sphere with lasers, they heat the inside of both ends of a gold tube (holhraum). This causes a bath of x-rays to uniformly heat a glass sphere that contains your fusion fuel. That glass sphere needs to be suspended in the center of the tube, but any inconsistency can cause huge knock on effects on yield. So they hold it between two <1um thick sheets of plastic. But if you can imagine, part of the sphere will be in contact with this plastic and part will not. That adds some reduction in how uniformly you heat the glass sphere.

But let's back up, how do they even make this perfect sphere of glass that is hollow? And how big is it? Well the sphere can be anywhere from 420um to 800+ um in diameter. From what I recall, the only way to make these is to drop small amounts of glass from a tall tower into water. Then do metrology on it, and toss away >90% of them right off the bat. Another issue is that some of the fuel leaks out of this hollow glass sphere over time. So timing from when you load the target from storage to actually firing the lasers can have non-zero effects on the yield.

Long story short. It's really hard to convey how close to the edge of precision ICF research is to the edge of micro fabrication. Now add the fact that some of these targets need to survive going from atmosphere to ultrahigh vacuum, and not break or tear... Remember that 1um thick plastic?

So yeah, no one is outsourcing this stuff. It's not being negatively effected by brain drain or lack of funding. It's just absurdly difficult to build to the designed tolerances the physics demands.

Fun fact, this is why a lot of physicists got behind the ITER project. The bigger you make something, the less important the minor fluctuations are to the overall yield. :D

sandworm1013• 4 years ago

We should never forget who pays the bills here. Laser fusion, in the context of the NIF, means weapons research. It might seem unrelated, but using radiation/lasers to collapse metals onto hydrogen to initiate fusion is the literal core of modern nuclear weapons research. This is not about electrical energy production.

cwillu• 4 years ago

“Activities are about one thing and one thing only” is a fallacy.

It's good to remind people about weapons research interests. It's less good to completely dismiss the interests concerning energy production, or basic scientific research. They don't go away just “omgz military funding!”

simiones7• 4 years ago

There are no true interests concerning energy production related to inertial confinement fusion. It is completely impossible for ICF to ever have a cost/watt that would make it even remotely economical. A coal power plant burning diamond instead of coal would almost certainly have better economic fundamentals than ICF can hope to achieve.

So this is weapons research and basic physics research caked in the language of power generation.

bananapub2• 4 years ago

where in the world have you seen anyone that is planning to try to use inertial confinement fusion for energy production?

yarg• 4 years ago

You're not completely wrong, but there's a history of viable technologies being eschewed in favour of those with military applications.

MomoXenosaga• 4 years ago

Nuclear power plants themselves are an offshoot of nuclear weapons. And there's a reason why they all produced weapons grade plutonium.

bismuthcrystal• 4 years ago

Chicago pile came before the trinity test.

DennisP4• 4 years ago

The US does not use civilian nuclear reactors for nuclear weapons production.

ch4s3• 4 years ago

This is a bit of a myth. Centrifuging and specific breeder reactors are much more useful for weapons production than any civilian power plant.

jonnycomputer• 4 years ago

Access to cheap, clean abundant energy is also a national security concern.

emaginniss• 4 years ago

The US military laid the groundwork for the internet. And yet, here you are.

Trouble_0072• 4 years ago

Lawrence Livermore National Laboratory (LLNL) : https://en.m.wikipedia.org/wiki/Lawrence_Livermore_National_...

sandworm1013• 4 years ago

Who are funded by DOE.

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

Who are in charge of nukes.

upsidesinclude• 4 years ago

The interesting thing here is that publications like Nature continue to release this kind of nonsense. The PR campaign being run to keep these places operating must cost a much as the research

simiones7• 4 years ago

It's very funny to read that they couldn't even replicate the initial experiment, while there were scientific articles imagining how this could be a realistic power source given "modest assumptions" about how the hohlraums can be industrially cheaply built.

JackFr• 4 years ago

Omar Hurricane is an outstanding name.

rbanffy• 4 years ago

We should call him Doctor Hurricane. He must have heard this joke a million times already. He might be one suck joke away from becoming a supervillain.

pfdietz8• 4 years ago

He could rock you.

ohiovr• 4 years ago

Fusion is hard. I thought of another use for that laser:

Take a small cylinder of pyrolytic graphite (it is diamagnetic, repelled by magnets) milled to be in the ideal axis and polystyrene layered in it. Then shoot it into a somewhat large ring of powerful magnets that have a trough in them to such a degree that it can trap the cylinder as it accelerates around the loop. The cylinder is propelled by successive shots of laser bursts that are not powerful enough to ablate (but close). One of the electromagnets can be quickly deactivated to allow for the cylinder to escape. Then it travels for a safe distance into very large lead target. Fusion could proceed if the speed is fast enough as the fuel is inertially kept together and friction should raise it’s temperature. If it produces neutrons, they will be absorbed by the lead. You can just collect the heat.

Edit. I think the lead target would be a no go. It would be no different than a bullet hitting a soft block of lead. Better would be a block of silicon carbide with some kind of borehole made of tungsten metal with fuel packed at the end of it. So the rice sized cylinder of nuclear fuel shoots right into the borehole and before the material can squeeze itself out, it has to overcome the enormous inertia keeping it going in one direction. Might be better though if the target itself was fuel. And it would be much easier to fuse lithium dueuteride than hydrogen and carbon.

I seem to recall a recent story on HN about something similar. So it isn't really a new idea. Perhaps making it run a circular course is different or that it doesn't use ablation for propulsion, it uses light pressure. I think the project was in the UK.

Laser fusion facility heads back to drawing board

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