Major Nuclear Fusion Milestone: Ignition Achieved

[phyzguy]

TL;DR

Recent article claims ignition has been achieved at NIF

https://phys.org/news/2021-08-major-nuclear-fusion-milestone-ignition.html

Anybody know any more? Like what they did differently from earlier trials.

 

[hutchphd]

From the article:
The results from the experiment on 8 August (2021) indicate an energy output of over one mega-joule, which marks the threshold agreed for the onset of 'ignition' and is six times the previous highest energy achieved.

And at no time did they prognosticate a future time frame and so win credibility points with me on that alone

 

[berkeman]

Summary:: Recent article claims ignition has been achieved at NIF

https://phys.org/news/2021-08-major-nuclear-fusion-milestone-ignition.html

While the latest experiment still required more energy in than it got out, it is the first to reach the crucial stage of 'ignition', which allowed considerably more energy to be produced than ever before, and paves the way for 'break even', where the energy in is matched by the energy out.

Sorry, after reading your link and others, I'm not clear what the fundamental difference is from previous shots. What does the term "ignition" technically mean? They've been getting some fusion all along from their shots, just not as much as for these latest shots, right? But it sounds like some large milesone has been reached with them using that term?

Thanks.

 

[TeethWhitener]

Sorry, after reading your link and others, I'm not clear what the fundamental difference is from previous shots. What does the term "ignition" technically mean? They've been getting some fusion all along from their shots, just not as much as for these latest shots, right? But it sounds like some large milesone has been reached with them using that term?

Thanks.

https://en.m.wikipedia.org/wiki/Fusion_ignition
Science also has a pop piece on it (claiming 70% of ignition):
https://www.sciencemag.org/news/202...lt-laser-powered-fusion-effort-nears-ignition

 

[berkeman]

https://en.m.wikipedia.org/wiki/Fusion_ignition

Fusion ignition is the point at which a nuclear fusion reaction becomes self-sustaining. This occurs when the energy being given off by the fusion reactions heats the fuel mass more rapidly than various loss mechanisms cool it. At this point, the external energy needed to heat the fuel to fusion temperatures is no longer needed.[1] As the rate of fusion varies with temperature, the point of ignition for any given machine is typically expressed as a temperature.

So this is the first time that a whole pellet has burned up after the initial impact of the shot? I guess I figured that it had already been achieved, but if this is the first time I guess that would be a good milestone.

But it also sounds from the links like the NIF is focused on fusion for military reasons, and not so much for energy production? In that case, is "ignition" some milestone in weapon's research? Maybe it allows smaller, lighter fusion warheads?

 

[TeethWhitener]

As far as I’m aware, they didn’t even burn up the whole pellet in this shot. It’s just that they got an order of magnitude more energy yield out of this shot than previously. It seems that they don’t know why it happened, either.

Also, I think NIF is formally charged with safeguarding the nuclear stockpile. I’m not entirely sure how it relates to weapons research, but in theory it enables direct examination of ignition without having to blow up an H bomb.

 

[phyzguy]

The attached paper is the last I paid attention to it, from 2013. At that time they were achieving about 0.1 MJ of fusion energy output. It sounds like this latest shot achieved ~1.0MJ of fusion energy output, so a big improvement. Presumably this is near the red star in Figure 2 of this paper.

I agree with @TeethWhitener that it is unlikely they burned the whole pellet, otherwise the energy output would have been significantly higher.

I don't think it's true that NIF is focused primarily on weapons research. Inertial confinement fusion can be made into a commercial reactor, although big improvements would need to be made.

 

[berkeman]

I agree with @TeethWhitener that it is unlikely they burned the whole pellet, otherwise the energy output would have been significantly higher.

I don't think it's true that NIF is focused primarily on weapons research. Inertial confinement fusion can be made into a commercial reactor, although big improvements would need to be made.

Yeah, I was assuming that they burned up the whole pellet when I made that comment. If they still have lots more improvement that they can achieve per pellet, and can improve the duty cycle of the shots, then maybe there could be some energy production possibilities. It didn't seem like they pushed that aspect at all from the parts of their announcement that I read.

 

[phyzguy]

This article in the BBC says they actually achieved 1.35 MJ of fusion energy. I'm impatiently waiting to see the papers to see what they did differently

 

[Astronuc]

NIF is focused on fusion for

radiation effects from high energy neutrons with photons of a range of energies. Well defined and monitored experiments are often used to benchmark codes.

To put the accomplishment in perspective, the output of 1.35 MJ is an improvement over previous efforts.

However, a couple of issues to keep in mind. First, the energy output is less than the energy input. Apparently, a typical input is about 3 MJ. At least that's a number from late 2020 with upgrades to the system, but it's a reasonable number.

Secondly, consider a typical modern nuclear plant operating around 3.65 GWt (or 3650 MWt, or 3650 MJ/s) generating 1.170 GWe, or 1170 MWe, or 1170 MJe/s.

The expectation for a system like NIF is to get to an output like 20-30 MJ per shot, and then they would need several hundred shots per second to produce the output of a large capacity nuclear plant. Or say, 100 shots per second to get 2 - 3 GW, assuming such a system can achieve 20 - 30 MJ per shot.

 

[mfb]

"Ignition" is the approximate range where fusion provides enough energy to lead to more fusion. 1.9 MJ laser power leading to 1.3 MJ fusion is certainly in that general range. It's nice to see that improvement, but even if they reach 1.9 MJ it's largely a symbolic milestone. Their capacitor banks store 400 MJ for each shot for the main laser amplification stage alone. After each shot the amplification crystals need to cool down for hours.

To be used for a power plant they would need to increase the overall efficiency by a factor ~1000-10,000, and increase the repetition rate by a factor ~100,000 to 1,000,000.

 

[Astronuc]

Their capacitor banks store 400 MJ for each shot for the main laser amplification stage alone. After each shot they need to cool down for hours.

That negates a power plant.

 

[Gordianus]

I love lasers and I've worked with them since 1978. 43 years ago I heard laser fusion was around the corner but I´m still waiting. Somehow I feel these giant lasers are a way of testing weapons without infringing treaties.

 

[bob012345]

It just means the funding cycle is coming up.

 

[berkeman]

It just means the funding cycle is coming up.

I've got two buttons in front me on my Mentor keyboard: [A] Infraction for Conspiracy Theory and [2] the Like button. Decisions, decisions...

 

[bob012345]

"Ignition" is the approximate range where fusion provides enough energy to lead to more fusion. 1.9 MJ laser power leading to 1.3 MJ fusion is certainly in that general range. It's nice to see that improvement, but even if they reach 1.9 MJ it's largely a symbolic milestone. Their capacitor banks store 400 MJ for each shot for the main laser amplification stage alone. After each shot the amplification crystals need to cool down for hours.

To be used for a power plant they would need to increase the overall efficiency by a factor ~1000-10,000, and increase the repetition rate by a factor ~100,000 to 1,000,000

Are lasers really only about 0.5% efficient? Even so, it is very impressive and so much more efficient than the sun on a volumetric basis.

 

[mfb]

You can make CO2 lasers with ~20% efficiency or so if I remember correctly, but they won't have the very short pulses NIF needs.

 

[Gordianus]

Laser diodes have the largest efficiency at 50%. The venerable CO2 achieves some 20%. Last time I read something about the NIF, they were using flash lamp pumped Nd:Glass amplifiers; a highly inefficient laser. Somewhere I read they were considering switching to laser diode pumped amplifiers (but I'm not so sure).

 

[bob012345]

According to the Wikipedia article;

Early reports estimated that 250 kilo-joules of energy was deposited on the target (roughly 2/3 of the energy from the beams), which resulted in a 1.3 Megajoule output from the fusing plasma.

Of course the NIF is focused on it's laser and laser based fusion physics and isn't tasked with inventing practical fusion reactors as others are. But the above quote begs the obvious question if 250 kJ of the output energy of one shot could be diverted to the next shot in a suitable design forming a controlled chain reaction and if so what would be the cost of creating a pellet vs. the value of the ~1 MJ of energy output even assuming the conversion was fairly efficient?

 

[mfb]

You need the energy in an extremely symmetric pattern around the fuel in an extremely short time (nanoseconds). You can't use one pellet to help with another pellet.

they were using flash lamp pumped Nd:Glass amplifiers; a highly inefficient laser.

Highly inefficient, but they can handle the high power (~500 TW at the target, it's more complicated during the amplification stages).

 

[Twigg]

Somewhere I read they were considering switching to laser diode pumped amplifiers (but I'm not so sure).

That'd be one mean diode amp...

I can't fathom the scale of the flashlamps they must use for the Nd:glass amps. Yikes...

 

[trainman2001]

I'm confused… are there two NIFs? I believe that the USA has an immense facility at Livermore, but this article is talking about one in the UK. The US facility's goal was to predict fusion reactions without having to build bombs. It is a defense oriented facility. Any power generation benefits would be extras as I see it.

https://lasers.llnl.gov/news

 

[berkeman]

I'm confused… are there two NIFs? I believe that the USA has an immense facility at Livermore, but this article is talking about one in the UK. The US facility's goal was to predict fusion reactions without having to build bombs. It is a defense oriented facility. Any power generation benefits would be extras as I see it.

https://lasers.llnl.gov/news

The link in the OP is for the NIF at LLNL, as stated in the article:

A new experiment appears to have triggered ignition for the first time, at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in the US, recreating the extreme temperatures and pressures found at the heart of the Sun.

And the link in your post appears to also be about the NIF at LLNL. Where are you seeing it referring to a Euro facility? Your link does seem to also have some links to other facilities, but not about this recent news item I don't think...

 

[Astronuc]

about one in the UK.

The UK contribution to Inertial Confinement Fusion takes place at the http://www.stfc.ac.uk/research/our-science-facilities/hiper/ and AWE as well as universities co-ordinated through an Inertial Fusion Network. The leading world activity in Inertial Confinement Fusion is taking place at the National Ignition Facility, USA with whom a number of collaborations with Imperial College London and the University of Oxford were recently funded.

https://epsrc.ukri.org/research/our...ramme/what-the-energy-programme-funds/fusion/

https://royalsocietypublishing.org/doi/abs/10.1098/rsta.2020.0012

In the absence of net power generation, such systems can only provide high energy density and radiation (neutrons and gammas) from the d+t reaction.

Fusion Supports the Stockpile - https://lasers.llnl.gov/news/fusion-supports-the-stockpile

Mark Herrmann, Livermore’s Deputy Program Director for Fundamental Weapons Physics, notes, “NIF provides us with experimental data in the higher-end temperature, pressure, and density regimes to measure our computer models against and provides insights into weapons performance.”

 

[trainman2001]

I just read it improperly. It's good to know there's only one NIF. I've been following that site for years. Interesting to note that they're still making progress.

 

[artis]

I think it is safe to assume that NIF and the approach they use will never become a practical fusion power plant , so given a layman can understand this I think they know they are working for a totally different purpose...

Even if they manage to get more energy out (electrical) from each shot and pellet than they put in via the lasers , which is I'd say rather impossible given the layout of the pellet fusion chamber and not close to breakeven for laser energy in - thermal energy out , they would still succumb to a very slow repetition rate since the pellet is a physical ball which needs to be replaced , not to mention what @mfb said about the time the lasers take to cool, and even if they use different lasers the power supply would probably need some time to "charge up" given how much energy it takes to drive a single shot.

1) @mfb can maybe also answer , if those laser crystals need so much time to cool after a single shot , and the shot itself lasts (ns?) then how in the world they don't crack or explode to pieces at the moment of the pump? What is the rate of temp increase under such a fast and powerful energy discharge? Or is it that they simply use a lot of parallel smaller ones and then combine the beams?But one thing somewhat intrigues me , what new physics do they hope to see at NIF with regards to H bombs and thermonuclear fusion that hasn't already been found by theory and other fusion experiments and the numerous H bomb detonations both by US and USSR alike?
One thing I can imagine is a much better access to the process of radiation ablation and implosion , a process that happens similarly in the H bomb only the source of photons is a laser instead of an A bomb and the radiation wavelength is I think higher at NIF.
So at NIF they can utilize the open geometry and poke all kinds of sensors and cameras to capture the implosion fusion, I think even more than they can in Sandia's Z machine , since that approach has a metal liner.

 

[mfb]

The heating happens throughout the volume, the cooling only happens at the surface. They use many big crystals.

I think it is safe to assume that NIF and the approach they use will never become a practical fusion power plant , so given a layman can understand this I think they know they are working for a totally different purpose...

In the past NIF has posted some material about producing electricity using that method. Didn't see that recently.

NIF should have some publications that you can check. Some parts will be secret of course.

 

[Oldman too]

Summary: Recent article claims ignition has been achieved at NIF

https://phys.org/news/2021-08-major-nuclear-fusion-milestone-ignition.html

Anybody know any more? Like what they did differently from earlier trials.

Some recent papers on that ignition claim.
https://physics.aps.org/articles/v15/67

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.075001

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.106.025202

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.106.025201
https://journals.aps.org/pre/pdf/10.1103/PhysRevE.106.025201

 

[Astronuc]

In the past NIF has posted some material about producing electricity using that method. Didn't see that recently.

I believe that was wishful thinking, and it was used to justify the expense to build such a facility.

I understand that the method is impractical for energy generation, but can be used for obtain a relatively high flux of high energy (~14.1 MeV) neutrons.

As I recall from about 4 decades ago, inertial confinement systems imagined a pellet per second (or so) dropping into a chamber and then blasted. At the time, I wondered how a burst would affect subsequent pellets arriving at the target location.

If it takes seconds, minutes, hours for the lasers to cooldown and the power system to recharge, then the idea is very impractical for energy generation, setting aside the fact that the system only generates a fraction inputted energy.

 

[hutchphd]

You mean I shouldn't have sold my oil stocks? Rats...fooled again