Big announcement about fusion energy coming soon (Dec-2022)

[berkeman]

An off-topic subthread has been deleted, and the thread is reopened (that subthread may be posted as a new thread if the participants want to do that, most likely in the GD forum and not Nuclear Engineering).

Please remember to stay on-topic for this Fusion Announcement thread. Thanks.

 

[Astronuc]

Record Energetics for an Inertial Fusion Implosion at NIF (through 2020)
https://link.aps.org/accepted/10.1103/PhysRevLett.126.025001

Nice summary and some details on earlier trials before 2021.

The basic principle of ICF is to use a powerful driver
to rapidly compress the fuel to fusion-relevant temper-
ature and density conditions [3]. Most ICF approaches
pursue hot-spot ignition [4], in which the fuel is initially
layered cryogenically on the inner surface of a capsule.
The drive rapidly ablates the capsule material, imparting
inwardly-directed velocity in the deuterium-tritium (DT)
fuel layer, which stagnates at the center creating high
pressures in a central ‘hot spot’ created via compression
of the initial vapor and ablation of the inner fuel layer.
Hot-spot ignition has large theoretical fusion energy gains
if the fuel can be compressed symmetrically with low
entropy. Multiple driver schemes have been developed
including laser indirect drive, where the laser energy is
converted to x rays in a radiation cavity (‘hohlraum’),
laser direct drive [5, 6], and magnetic direct drive [7, 8].
Significant understanding of these challenges has been
developed at the National Ignition Facility (NIF)[9] for
the laser indirect drive approach, including successes in
implosion control that have led to net gain from the fuel
and significant yield amplification from self-heating [10–
15]. However, these implosions have reached limitations
short of the burning plasma regime [16], and the current
program is focused on improving performance towards
this milestone.

 

[artis]

So here are some details of why apparently this last shot was the most energy yielding of all the previous ones.
https://lasers.llnl.gov/news/high-quality-diamond-capsule-enhanced-nifs-record-energy-shot

From the reading I notice 2 main takeaways
1) Pellet outer layer (pusher /tamper) made out of synthetic diamond to reduce the layers impurities mixing with the fusion fuel once it reacts

The capsule had 10 times fewer surface holes, or pits, and subsurface voids, as well as fewer contaminating high-Z (high atomic number) inclusions, than the capsule used in NIF’s previous record-energy experiment in February 2021, which produced only one-eighth the energy of the August shot. The capsule defects were thought to substantially contribute to the amount of capsule material mixing into the imploding fuel, preventing it from being compressed properly and reducing the hot-spot fusion rate below that required for ignition.

Also they made the capsule/pellet outer layer feed hole smaller which is used for filling the inner void with DT mixture.

A tiny two-micron-diameter fill tube was used to inject deuterium-tritium (DT) fuel into the capsule, limiting the tube’s contribution to implosion instabilities. The February shot used a five-micron fill tube—itself much thinner than the tubes used in early NIF experiments, which ranged from 10 to as much as 44 microns in diameter.

2) They also decreased the size of the axial openings at each end of the "hohlraun" high Z cavity , the inner walls of which emit X rays after being bombarded with the UV photons from the lasers, this apparently minimized radiation leakage from the holhraum

A new hohlraum design with smaller laser entrance holes limited the loss of energy escaping through the holes during the implosion, improving hohlraum efficiency—the amount of energy coupled to the capsule—and enhancing the fuel compression and hot-spot pressure

Here is a video about it (also present in the upper link)

Here's one personal curiosity from me, those knowledgeable can maybe answer it.

It is known from literature (at least the open literature) that the "pusher/tamper" of a thermonuclear bomb secondary which is identical in principle to the NIF capsule/pellet outer layer is made from a high Z material in the H bomb case for various reasons but mainly so that the X rays that impact it don't go through to the fuel inside and cause pre heating of it. The material is opaque to the radiation to cause successful ablation without preheating of the fuel. The radiation temperature within the radiation channel therefore demand a high Z material.

In NIF case the outer layer is of low Z material. Could this be because NIF radiation is of much lower energy than that of a H bomb radiation case therefore the a low Z material suffices as opaque and preheating doesn't happen?

This is the first guess from me myself. A food for thought.

 

[Astronuc]

mainly so that the X rays that impact it don't go through to the fuel inside and cause pre heating of it. The material is opaque to the radiation to cause successful ablation without preheating of the fuel.

It's more the case that one wants the 'ablation' layer to absorb the maximum energy in order to maximize temperature in a as short a time as possible, so that it will ablate. High Z materials attenuate X-rays and electrons because the atoms have Z electrons. Light elements like H, Li, Be, B, C, N, and O do not attenuate radiation (electrons and X-rays) as well as higher Z elements like Ti/V/Cr/Fe/Ni/Cu, Zr/Nb/Mo, Hf/Ta/W or Th/U; the higher the Z, the more effective the attenuation. The added issue with U is the matter of fission, which would mean processing fission products after the shot would defeat the goal of producing energy without fission products.

Nevertheless, there will be plenty of activated (radioactive) elements in the system, since d,t produce n (14.1 MeV) and alpha (3.5 MeV), and those neutrons not absorbed in a Li blanket would be absorbed by the surrounding structural material(s), including the holder.

As part of my current research, I just happen to be looking at attenuation of gammas and electrons of the same energies in a variety of materials. Three observations are: 1) gammas are more penetrating than electrons of the same energy, 2) the higher the Z the greater the attenuation at a given energy, and 3) the higher the energy of gamma rays, the more likely they scatter in the forward direction.

Gammas (and X-rays) interact with atomic electrons by Thomson/Rayleigh scattering, photoelectric effect (absorption) or Compton scattering. Thomson/Rayleigh scattering and photoelectric effect dominate at low energies, while Compton scattering becomes more important as energy increases (> 100 keV) to a moderate range. As photon energy increases beyond 1.022 MeV (2*m_e), pair production becomes important, and the energy at which the probability of pair production equals that of Compton scattering depends on Z.

https://www.nde-ed.org/Physics/X-Ray/attenuation.xhtml
https://radiologykey.com/x-ray-imaging-fundamentals/

 

[sophiecentaur]

OK, if this were to pan out and become a viable source of energy, what would that do to all the schools now currently investing in hydrogen-energy research?

There are two separate issues here. Fusion is a potential source of carbon-free energy. This needs to be stored when wires are not long enough.
Chemical methods are favourite in many respects. There are many options for this. Batteries are convenient but require high mass and scarce chemicals. Carbon compounds would be convenient (IC engines) and could involve no net carbon production if they were made from electricity. But there could / would be local pollution.

BUT Hydrogen could be used in fuel cells and / or IC engines and produce only waste water. There is no present method (afaik?) that would make small scale (cordless appliances) Hydrogen energy storage practicable. So we could be stuck with IC engines or batteries for some while for many purposes.

 

[hutchphd]

BUT Hydrogen could be used in fuel cells and / or IC engines and produce only waste water. There is no present method (afaik?) that would make small scale (cordless appliances) Hydrogen energy storage practicable. So we could be stuck with IC engines or batteries for some while for many purposes.

Of course were there really to be a meaningful breakthrough in any avenue (fission or fusion or Psychokinesis?) fronts the question of local delivery thereof is simply detail: to be worried about after the huge party we could all have. (Drinks on me.)

 

[berkeman]

or Psychokinesis

You can raise my hand in support of that!

 

[hutchphd]

I'll do my best.......any time now....

 

[artis]

It would have been difficult to imagine a Boeing 747 had you been on a Kitty Hawk Dune in 1903.

I think this might be debatable , some technology just isn't as doable as other.
James Chadwick published his research on the neutron in 1932 then by 1942 Fermi had built the first nuclear fission reactor Chicago pile 1. So that's 10 years, then as we all know plutonium production reactors were already working in Hanford around 1944 and by 1945 we had the first fission bombs.
So a timeline of roughly 15 years.
Fusion is a different story , some technology is much harder to attain due to the constraints of laws of nature, so I wouldn't be so optimistic that my fusion skepticism is just one of those "haters gonna hate" moments of pop culture, there is a lot of hard fact and science to back up that urban legend of 30 years away.

Economically speaking fusion currently is worse than Sam Bankman Fried's Alameda research in the sense that all money that goes in, none comes back out. I think that is one of the reasons why investors have been reluctant to give more. That's also the reason why governments should take up such hard long term projects more.
But complicated science needs sacrifice , no way around that.

 

[artis]

First of all , thanks @Astronuc for your post #104, I did not know that X ray tubes, the kind used in medical imaging were only 0.009% efficient! That is worse than an incandescent bulb. I do understand the reason why.
https://radiologykey.com/x-ray-imaging-fundamentals/

For energy levels used in diagnostic medical imaging, the vast majority of incident energy is converted to heat. As an example, for 100 keV electrons colliding with tungsten (Z = 74), the approximate ratio of radiative to collisional losses is (100 × 74)/820 000 = 0.009 or 0.9%. Therefore, about 99.1% of the incident energy will be released as heat.

Makes one wonder why they don't use B field for magnetic bremsstrahlung X ray production like one does in a free electron laser and other niche vacuum apparatus. That is more efficient.

It's more the case that one wants the 'ablation' layer to absorb the maximum energy in order to maximize temperature in a as short a time as possible, so that it will ablate. High Z materials attenuate X-rays and electrons because the atoms have Z electrons. Light elements like H, Li, Be, B, C, N, and O do not attenuate radiation (electrons and X-rays) as well as higher Z elements like Ti/V/Cr/Fe/Ni/Cu, Zr/Nb/Mo, Hf/Ta/W or Th/U; the higher the Z, the more effective the attenuation.

Could it also be the case that during the radiation implosion the low Z pellet surface material is ionized so fast that it becomes a plasma and therefore shields the contents of the pellet from X rays better than it would in it's solid form?
I recall reading that the NIF X rays are in the energy spectrum of roughly 100 to 300eV , I wonder if they were in the keV range then the use of low Z pellet ablator would not suffice anymore most likely?

 

[artis]

To continue with what's already said, I went through some materials to refresh what I knew of NIF and to learn new stuff and here's what I found.

There are two energy transfer efficiencies that are important when compared to the final plasma energy out.
Mostly people talk of the laser "wall plug" efficiency which for most lasers is low and for the NIF laser is roughly 1% IIRC. Sure there is room for improvement there.
But there is another efficiency in conversion and that is the laser to X ray conversion and X ray energy to ablation pressure coupling efficiency. Since what matters for fusion is only how much pressure can be given to the imploding pellet from the X rays that ionize/heat the ablator that forms the plasma that then ejects mass from the ablator causing a "action/reaction" that drives the ablator inwards.
Here is a picture from wiki for which I searched some references for backup and seems to be true.

So at best only 20% of the laser energy is actually coupled to the implosion event itself.
This makes the recent result more spectacular in a way because the delivered laser energy - roughly 2.05MJ , only 20% at best went into the actual implosion so about 0.4MJ for the roughly 3 MJ out. At least this is what my rough calculation gives me.Here is a nice article (start of 2022) from nature which also speaks about the details of the implosion, it also confirms the laser energy to implosion coupling efficiency.
https://www.nature.com/articles/s41586-021-04281-w

The exposed surface of a capsule at the centre of the hohlraum absorbs approximately 10–15% of the X-rays, causing the outer edge of the capsule (the ablator) to ionize, generate high pressures of the order of hundreds of Mbar (1 Mbar = 1011 Pa), and expand away from the capsule—a process termed ablation.

The nature article also states that

The achievement of a burning-plasma state is key progress towards the larger goal of ‘ignition’ and overall energy gain in inertial fusion. The fusion yields reported here (approximately 0.17 MJ) are lower than the input laser energy (approximately 1.9 MJ), but are nearly equal to the capsule absorbed energy (giving capsule gain of about 0.7–0.8) and are an order of magnitude greater than the input energy transferred to the fusion fuel.

Which sort of makes the same point I just said that if we only look at the final stage from the actual energy that the pellet ablator receives/couples from the Laser then the last shot looks much better as it only coupled roughly 0.5MJ from the total 2MJ laser pulse that entered the hohlraum but the fusion yield of it was 3Mj , so it's 0.5MJ vs 3 in that sense. 0.5 to 3 is a gain of 6 by the way. But fair enough NIF calculates the gain from the laser energy to the hohlraum VS fusion yield so that is only 2 vs 3 a gain of 1.5The problem part is this , it seems hard to further increase the coupling efficiency. I read there are various paths how the initial laser energy is lost.
Here are a couple

1) Laser strikes hohlraum inner high Z (Gold and Uranium) walls and that creates a plasma which then interacts with the laser light to partly scatter it away, some 2% of this is backscatter in the direction of the incoming laser light and exits back out the hohlraum axial entrance windows.

2) Since the hohlraum inner wall is lined with high Z materials , as @Astronuc already said , they attenuate the photon energy so some of it is lost to heat and X rays that are outside the preferred X ray energy spectrum and some of those X rays get lost too.

Also one disruption mechanism that I read they experienced early on was that the laser hit inner wall of the hohlraum created uneven plasma bursts that then created uneven radiation flux in the cavity and sometimes the plasma even physically touched the ablator surface.
So alot of work has been put into perfecting all of this it seems, from making different hohlraum geometries to changing individual laser beam wavelength etc.

They also created a rugby shaped hohlraum for these purposes , see the link
https://lasers.llnl.gov/news/frustraum-hohlraum-design-is-shaping-up

This seemingly increased the coupling efficiency of X rays to the ablator.

Previous research using a hohlraum shaped like a rugby ball increased the level of laser-induced energy absorbed by a single-shell ICF fuel capsule to about 30 percent. That is about double the level of energy absorption — known as energy coupling — of 10 to 15 percent with a standard cylindrical hohlraum used at NIF.

This rugby shaped cavity they call a "frustraum" instead of a hohlraum.

Also the targets are manufactured by hand in what seems like a long and slow process. One can read more about that in this link.
https://www.cambridge.org/core/jour...-nif-targets/2F53CD97D5DCB494E70C1E428F6D056F

What is also interesting is that they glue in various polymer seals where the diagnostics ports are located on the target because the larger spherical room which hold the hohlraum holder is under vacuum but the small "target" hohlraum is actually filled with He gas.
This is done to create a more even radiation flux it seems and suppress the hohlraum inner wall plasma eruption instabilities. This He gas filling seems rather similar in principle to the fill method used in actual H bombs to help even out the radiation flux emanating from the primary within the hohlraum aka radiation channel, in the bomb case that material is a classified one and known officialy only as "fogbank". Prior to shot the He helps to cool the pellet inside as it couples to the hohlraum walls which themselves are cooled by the holder "hand" that it is attached to.

For tamping purposes, the hohlraum is filled with a gas such as He, typically at sub-atmospheric pressures. As described in more detail later, we cool the hohlraum by conductively connecting it to the cryostat and the He inside also serves to cool the capsule accordingly. When the target is fielded on NIF, it is held at high vacuum within a shroud, which is a clamshell structure that protects the target from the ambient till close to shot time at which point the shroud is splayed open allowing full visibility of the target to the laser beams

Apparently the link also talks about the targets leaking some He gas into the larger vacuum chamber and how much leaking is acceptable.

And lastly the data acquiring for better models that @Vanadium 50 mentioned earlier here
https://lasers.llnl.gov/for-users/experimental-capabilities/materials

An interesting video animation from LLNL about how they "X ray" the imploded target for information about the conditions within it.

 

[artis]

Here is an article from LLNL about axial magnetic fields through the target.
https://lasers.llnl.gov/news/magnetized-targets-boost-nif-implosion-performance

The method even patented by their senior staff member John Moody.And here is an interesting blog piece about some of NIF physics.
https://lasttechage.com/2015/06/14/nif-notes_hohlraum-spring-2015/

 

[gmax137]

Not sure if this piece in the Bulletin of Atomic Scientists has been linked to yet:

"A recent breakthrough in nuclear fusion captured global attention, but what does it mean?

"Physicist Bob Rosner explains why this is a huge achievement - and why it has more to do with nuclear weapons than nuclear energy:
https://bit.ly/3uWA2Cn

 

[artis]

The primary purpose of NIF is to get that data.

Not sure if this piece in the Bulletin of Atomic Scientists has been linked to yet:

"A recent breakthrough in nuclear fusion captured global attention, but what does it mean?

"Physicist Bob Rosner explains why this is a huge achievement - and why it has more to do with nuclear weapons than nuclear energy:
https://bit.ly/3uWA2Cn

Rosner:

efforts were made to construct new simulation codes to help certify the weapons, and investments were made in new generations of advanced computers that these codes required and could run on. And NIF was meant to, in part, validate the design code approaches used for the weapons. Before NIF was even completed, they chose a target experiment that—in combination with simulation codes advances—could demonstrate that we knew what we were doing.

right on right on

 

[Astronuc]

"Physicist Bob Rosner explains why this is a huge achievement -

Rosner: Here’s my standard story, which actually comes straight from Marv Adams, because he said what I’m about to tell you: This facility can do one shot a day; this is at slightly more than two megajoules (of output). For an energy source, it would have to do the same thing at least 10 times a second. If you ask, “Do the lasers exist that can do this?” Not in your dream. The pellet cost a bit over $100,000 to manufacture.

I remember such statements about 40 years ago - in the conceptual phase. The hohlraums and pellets cost less then, but still a lot more than was economical. To obtain economical output, one would have to increase the energy output greatly, either by increasing the frequency of pellet ignition (10/s is woefully inadequate), increase the size of the pellet (changing geometry is a big deal and adds to complexity; one still needs to achieve the same sphericity requirements - consistently), and one needs to decrease the cost of the hohlraum and pellet by about a factor of 1000. And that doesn't address how to recover the thermal energy (80% of which is in fast (14.1 MeV) neutrons) and then convert to electrical energy, ostensibly in the same way as present systems - thermal > mechanical > electrical). The neutrons would have to be absorbed by a light element (e.g., Li to produce T), the fuel for the reaction in the first place (sustainability).

Perhaps other targets, e.g., full - D, or p-¹¹B, but how does one transport the thermal energy to a system that then converts the thermal energy to mechanical (turbine) to electrical (generator). It was a nutty idea then; it remains to.

 

[Astronuc]

So at best only 20% of the laser energy is actually coupled to the implosion event itself.
This makes the recent result more spectacular in a way because the delivered laser energy - roughly 2.05MJ , only 20% at best went into the actual implosion so about 0.4MJ for the roughly 3 MJ out. At least this is what my rough calculation gives me.

I've assumed that the ~2 MJ is the 20% of input to the pellet, i.e., the lasers produced 10 MJ (into the hohlraum) out of 400-600 MJ. In other words, ~2 MJ went into the pellet, which then produced an output of ~3 MJ (for a net gain of ~1.1 MU) in the Dec experiment. It occurs to me that with the ablation layer, half the energy absorbed (momentum produced) goes outward in order for the other half to go inward (probably more than half outward, so at least a 50% loss of energy going to the pellet).

The previous record (experiment N210808, August 8, 2021) of 1.3 MJ (or 1.35 MJ) from 1.9 MJ into the pellet (for 68% to 70% efficiency).
https://www.llnl.gov/news/three-pee...fic-results-national-ignition-facility-record

“Many variables can impact each experiment,” Kritcher said. “The 192 laser beams do not perform exactly the same from shot to shot, the quality of targets varies and the ice layer grows at differing roughness on each target. These experiments provided an opportunity to test and understand the inherent variability in this new, sensitive experimental regime.”

While the repeat attempts have not reached the same level of fusion yield as the August 2021 experiment, all of them demonstrated capsule gain greater than unity with yields in the 430-700 kJ range, significantly higher than the previous highest yield of 170 kJ from February 2021.

https://lasers.llnl.gov/news/three-...hlight-scientific-results-of-nifs-record-shot
See (b) in the figure showing the pulse height and width.

Still waiting for the details. The shot was on December 5, 2022, so I expect the designation is N221205.

After years of experiments that produced
energies in the kilojoule range, the fuel in
the peppercorn-sized capsule of the Aug. 8,
2021, shot yielded 1.35 megajoules (MJ),
eight times more energy than the previous
record shot and about 70 percent of the 1.92
MJ fired by NIF’s 192 lasers.

Ref: https://lasers.llnl.gov/content/assets/docs/news/reaching-the-threshold-of-ignition-magazine.pdf (2022)

 

[artis]

I've assumed that the ~2 MJ is the 20% of input to the pellet, i.e., the lasers produced 10 MJ (into the hohlraum) out of 400-600 MJ. In other words, ~2 MJ went into the pellet, which then produced an output of ~3 MJ (for a net gain of ~1.1 MU)

Are you sure of that?

I ask , because from what I read it seems to me that NIF can deliver at best a bit over 2MJ and that is the total UV laser power after upconversion , that enters the larger vacuum chamber sphere and down into the target to heat the small target hohlraum walls.

I base my assumption on these links, please see.

First of all this brochure from NIF mentiones the 2MJ

Then https://www-pub.iaea.org/mtcd/publications/pdf/csp_008c/pdf/if_3.pdf

The NIF is designed to deliver 1.8 MJ and 500 TW of 0.35-μm laser light to indirectly or
directly driven Inertial Confinement Fusion (ICF) targets

And then this interesting paper on the IAEA webpage , talking about the increased coupling efficiency with a rugby shaped hohlraum and larger pellet diameter.
https://nucleus.iaea.org/sites/fusi...s/FEC 2020/fec2020-preprints/preprint1190.pdf

They say that

The paper reports the first experiment at the NIF demonstrating ~ 30% energy coupling to a 3 mm-diameter high-energy-
density carbon capsule in a rugby hohlraum with a 2-shock laser pulse shape. By comparing the measured bang time with a
simulated hydrodynamic scaling, ~430kJ coupling is inferred with 1.36 MJ laser drive.

430kJ into the pellet from a total laser pulse of 1.36MJ seems to me like roughly 30%, so I take that 1.36MJ was the total laser energy delivered and 430kJ the absorbed amount of the rest being "wasted".
The article also says that

It was a 5ns-long 2-shock drive, with a total laser energy 1.36MJ in
the NIF shot N201116-001.

Nonetheless, with the total
laser energy of 1.36MJ, the total backscatter was only about 1% (up to 3%), which is not of a concern in terms of
optics damage

As E cap increases from 418kJ to 460kJ, the bang time decreases from
10.11ns to 9.44ns. The measured bang time with the experimental uncertainty is shown as the red band, which
corresponds to Ecap ~ 430-440 kJ, or ~30% coupling efficiency with 1.36MJ laser drive

 

[Astronuc]

I ask , because from what I read it seems to me that NIF can deliver at best a bit over 2MJ and that is the total UV laser power after upconversion , that enters the larger vacuum chamber sphere and down into the target to heat the small target hohlraum walls.

Well, it all depends on what is meant by 'deliver', or rather, where the 'delivery' of energy is being calculated. Is it into the hohlraum, or at the surface of the ablator, or actually into the pellet?

I'm still waiting for the details of the experiment, including how much energy was input into the laser system.

 

[artis]

Well, it all depends on what is meant by 'deliver', or rather, where the 'delivery' of energy is being calculated. Is it into the hohlraum, or at the surface of the ablator, or actually into the pellet?

I'm still waiting for the details of the experiment, including how much energy was input into the laser system.

I agree, and I also want to point out that with regards to NIF these parameters are not exactly clearly stated in many of their documents which brings forth some confusion.
But based on the papers I cited I do feel that they are talking about the total laser energy.

But with regards to the article that @gmax137 quoted , and besides to the points you already said, I would tend to also agree with Rosner that NIF is a far cry when it comes to a commercial energy production, the absolute precision that the target manufacturing and assembly requires coupled with not one but two fundamental conversion (IN)efficiencies , namely the laser wall plug efficiency and the laser to pellet coupling efficiency + the shot repetition frequency, it's I think too many problems to solve, at least currently.

 

[Astronuc]

Are you sure of that?

Is it into the hohlraum, or at the surface of the ablator, or actually into the pellet?

The LLNL literature states that the laser output is about 2 MJ per laser, or 384 MJ, or slightly higher. So the hohlraum input it about 384 MJ, and back NT210808, apparently obtained 477 MJ to get 1.9 (or 1.95 MJ) on the target (which I take to mean the ablator, or it means 1.95 through the ablator into the target, i.e., it is the thermal energy deposited into the target) from which they achieved an output of 1.3 or 1.35 MJ, or about 70% efficiency. To make any sense of the results, we need the details that are not yet published. With the 2 MJ on the target, based on 2 x 192 lasers, then the efficiency of laser to target is on the order of 1/192 or 0.0052.

It would be interesting to know how the applied magnetic field improved the input into the target (improved coupling of the X-ray into the ablator, or provide resistance to the ablator outward expansion for higher pressure around the target fuel), or perhaps increased the pulse width (basically, same power but wider plateau at peak energy) for more energy into the target, or a combination.

Then the question becomes: "What was the laser power input and output to achieve the latest shot (NT221205) and the previous record shot (NT210808). I would expect they have the data and could plot the energy pulse to compare, and they could mention laser energy input and output. However, that would indicate that this concept is not feasible for electrical generation, and probably never will be. Rather, it is an expensive neutron source as well as a source of condensed matter not usually seen in terrestrial systems.

There is this article on higher energy output from the lasers, or > 2 MJ.
https://lasers.llnl.gov/news/high-energy-shot-puts-nif-back-on-track-toward-ignition

In the Sept. 19 (2022) experiment, laser operators boosted NIF’s laser energy from 1.92 MJ on the Aug. 8 shot to 2.08 MJ, slightly more than the researchers requested. This was the first NIF shot to deliver more than two MJ of ultraviolet energy to an inertial confinement fusion (ICF) target.

The shot on Sep 19, 2022 would be NT220919.

 

[artis]

The LLNL literature states that the laser output is about 2 MJ per laser, or 384 MJ, or slightly higher. So the hohlraum input it about 384 MJ, and back NT210808, apparently obtained 477 MJ to get 1.9 (or 1.95 MJ) on the target (which I take to mean the ablator, or it means 1.95 through the ablator into the target,

I agree there's not much use debating details we don't know but if hundreds of MJ actually arrive at the hohlraum and 1.9MJ is only deposited on the ablator then that would be a coupling efficiency of less than 1% and that doesn't make sense to me.
The last place where the laser energy is reduced is in the UV upconversion plates where it is turned from IR to UV. After that whatever laser energy is left is delivered through the vacuum of the target chamber into the hohlraum.
And we do know ,as it is stated in many places, that the laser energy into hohlraum to target ablator deposited energy coupling is roughly 10-30% efficient depending on the details of the pellet size, hohlraum geometry etc.
So let's assume the lower 10% energy coupling. If say they normally have about 380MJ hohlraum input then by the 10% coupling that should put roughly 38MJ onto the ablator but I'm almost sure that doesn't happen.

I see figures like in the kJ range that get deposited on the actual ablator and they make sense in the 10-30% coupling range only if the total energy into the hohlraum is at max 2MJ.

But I might be wrong as I have read many NIF papers so far and none of them have this stated in one place and clearly, but I do feel based on what I've read so far that the hohlraum arrival beam total is the 2MJ figure. I believe that is also why they used this figure in the official press release as that is easier for the general public to understand.
But let's see.PS. On this one I actually believe wikipedia, it sort of coincides with the LLNL articles I've been reading and according to wiki NIF page it's mentioned in many places that the hundreds of MJ is the laser total energy in so that means energy from grid as compared to the actual energy out which would be the energy arriving in the target vacuum chamber.
So for their 2021 shot they got to use 477MJ and delivered roughly 2MJ to target and that is well below 1% which we know is the efficiency of that flashlight pumped laser.

https://en.wikipedia.org/wiki/National_Ignition_Facility
At the bottom of the page it says

Burning plasma achieved, 2021​

On August 8, 2021, an experiment yielded the world's first burning plasma.[125] The yield was estimated to be 70% of the laser input energy. It produced excess neutrons consistent with a short-lived chain reaction of around 100 trillionths of a second.[126] The material of the capsule shell was changed to diamond to increase the absorbance of secondary x-rays created by the laser burst, thus increasing the efficacy of the collapse, and its surface was further smoothed. The size of the hole in the capsule used to inject fuel was reduced. The holes in the gold cylinder surrounding the capsule were shrunk to reduce energy loss. The laser pulse was extended.[127] This result slightly beat the former record of 67% set by the JET torus in 1997.[128][failed verification] These numbers are the ratio of energy created by fusion against the amount of energy reaching the plasma. This is not the same as overall power in to power out. The experiment used ~477 MJ of electrical energy to get ~1.8 MJ of energy into the target to create ~1.3 MJ of fusion energy.[125]

An exact year later, on August 8, 2022, three new studies were published confirming the ignition of the plasma under the Lawson criterion in the original experiment

Breakeven, December 2022​

The NIF became the first fusion reactor to achieve scientific breakeven on December 5, 2022, with an experiment producing 3.15 megajoules of energy from a 2.05 megajoule input of laser light for an energy gain of about 1.5.[11][133][134][135] Charging the laser consumed "well above 400 megajoules".[136] In a public announcement on December 13, the Secretary of Energy Jennifer Granholm announced the facility had achieved ignition.[137]

The feat required the use of a slightly thicker and smoother capsule surrounding the fuel and a 2.05 MJ laser (up from 1.9 MJ in 2021). They also redistributed the energy among the split laser beams, which produced a more symmetrical (spherical) implosion

In these numbers the LLNL glance over the UV to X ray and X ray to ablator energy coupling efficiencies , they just have the laser electrical energy to laser UV energy and laser UV energy to fusion output energy numbers I believe.
The laser UV energy I take to be the total energy in all of the 192 beams as it is deposited in the hohlraum. The 2MJ figure.

 

[Astronuc]

From Science magazine - https://www.science.org/content/article/historic-explosion-long-sought-fusion-breakthrough

If gain meant producing more output energy than input electricity, however, NIF fell far short. Its lasers are inefficient, requiring hundreds of megajoules of electricity to produce the 2 MJ of laser light and 3 MJ of fusion energy. Moreover, a power plant based on NIF would need to raise the repetition rate from one shot per day to about 10 per second. One million capsules a day would need to be made, filled, positioned, blasted, and cleared away—a huge engineering challenge.

A huge engineering challenge should read a set of huge engineering challenges.

Huge engineering challenges include:
Lasers and laser efficiency (reduce laser heat up and cool down cycle)
Energy storage
Capsule design
Hohlraum design
Hohlraum holder (need a different holder for 10/s)
Magnet and Magnetic field design
Manufacturing of capsules and hohlraums at a rate of 1 million (or at least 864000) per day, or more than 10/s, and holding the defect rate to < 1E-5 and ideally, ~1E-6, consistently.

Radioactive waste disposal - those neutrons not absorbed by Li-6 (to produce T) will be absorbed by some other element in some structure, which then becomes radioactive.

Lastly, the conversion of thermal energy to electrical energy, with some unknown efficiency.

In the same article

The NIF scheme has another inefficiency, Betti says. It relies on “indirect drive,” in which the laser blasts the gold can to generate the x-rays that actually spark fusion. Only about 1% of the laser energy gets into the fuel, he says. He favors “direct drive,” an approach pursued by his lab, where laser beams fire directly onto a fuel capsule and deposit 5% of their energy. But DOE has never funded a program to develop inertial fusion for power generation. In 2020, the agency’s Fusion Energy Sciences Advisory Committee recommended it should, in a report co-authored by Betti and White. “We need a new paradigm,” Betti says, but “there is no clear path how to do it.”

Some context from April 1978 (44 years, 8 months ago).
https://www.science.org/doi/10.1126/science.200.4338.168 (purchase/subscription required)

Fusion, like solar energy, is not one possibility but many, some with very attractive environmental characteristics and others perhaps little better in these regards than fission. None of the fusion options will be cheap, and none is likely to be widely available before the year 2010. The most attractive forms of fusion may require greater investments of time and money to achieve, but they are the real reason for wanting fusion at all.

 

[artis]

Well "Betti" favored direct drive has it own set of problems which were part of the reason why NIF went the indirect drive way. Symmetry and timing being the biggest I think.

It would be interesting to know how the applied magnetic field improved the input into the target (improved coupling of the X-ray into the ablator, or provide resistance to the ablator outward expansion for higher pressure around the target fuel), or perhaps increased the pulse width (basically, same power but wider plateau at peak energy) for more energy into the target, or a combination.

From what I read, it seems they "premagnetized" the pellet so the field is already there as the ablator/tamper is pushing inwards. I think that an axial B field through fuel almost definitely helps in terms of confinement and IIRC that is also what some of the articles I quoted earlier said.
I do wonder though how it impacts the resistance (increased work) that the ablation layer plasma feels as it is pushed inwards.
I just checked , sadly the NIF link to where they talk about the target magnetization is down.
Here is a patent from their senior researcher/staff member John Moody and colleagues about the very method they have used.

https://patents.google.com/patent/US20140348283

In one embodiment, the present invention provides the application of axial seed magnetic fields in the range 20-100 T that compress to greater than 10,000 T (100 MG) under typical NIF implosion conditions and may significantly relax the conditions required for ignition and propagating burn in NIF ignition targets that are degraded by hydrodynamic instabilities. Such magnetic fields can: (a) permit the recovery of ignition, or at least significant alpha particle heating, in submarginal NIF targets that would otherwise fail because of adverse hydrodynamic instability growth, (b) permit the attainment of ignition in conventional cryogenic layered solid-DT targets redesigned to operate under reduced drive conditions, (c) permit the attainment of volumetric ignition in simpler, room-temperature single-shell DT gas capsules, and (d) ameliorate adverse hohlraum plasma conditions during laser drive and capsule compression. In general, an applied magnetic field should always improve the ignition condition for any NIF ignition target design.

 

[mfb]

The LLNL literature states that the laser output is about 2 MJ per laser

That's the input per laser, and the approximate total output energy in the 192 lasers combined. It is not the light energy per laser.

In the Sept. 19 (2022) experiment, laser operators boosted NIF’s laser energy from 1.92 MJ on the Aug. 8 shot to 2.08 MJ, slightly more than the researchers requested. This was the first NIF shot to deliver more than two MJ of ultraviolet energy to an inertial confinement fusion (ICF) target.

This is the sum of all 192 lasers.

 

[sophiecentaur]

A long way to go but these things can surprise us.
A similar long term thing is the pipe bots for coping with UK water leaks. There’s a date of 2050 for them.

 

[Nathi ORea]

Can I ask… how to they actually measure the amount of energy coming out of these machines?

 

[sophiecentaur]

Can I ask… how to they actually measure the amount of energy coming out of these machines?

It's probably based on measuring the heat output rate - water flowing round a water jacket and measuring temperature rise. A sophisticated version of what we did at school. Finding how much electricity can be generated is more complicated but, as with regular boilers and reactors, that's what really counts.

 

[artis]

It's probably based on measuring the heat output rate - water flowing round a water jacket and measuring temperature rise. A sophisticated version of what we did at school. Finding how much electricity can be generated is more complicated but, as with regular boilers and reactors, that's what really counts.

IIRC there is no water "jacket" or water flowing around the NIF hohlraum target chamber, at best it's cryogenically frozen by the holder arm into which it is put. That freezing excludes water at all I think.

I actually uploaded a video link where one of the methods of investigating capsule implosion (could also help in determining yield I suppose) was shown.

An interesting video animation from LLNL about how they "X ray" the imploded target for information about the conditions within it.

But mostly I would think they measure the neutrons produced since they know the fuel mixture within the reaction pre ignition that would allow them to calculate yield based on neutrons alone I think.

 

[artis]

When you think of it, the history of NIF can be compared to the average experience of an older diesel car owner in cold mornings,

For quite a long time there's no ignition, then you start seeing some ignition, then you get to nearly ignition and finally after "cranking" it for 3 decades you get ignition...Either way I took my inspiration for this joke from this 60 minutes video.
You can see some views of the actual holder arm that holds the hohlraum within which the capsule lies, also some nice commentary from fusion skeptics at the end and the pellet actual size and how hard it is to fabricate one.

 

[Astronuc]

I think the CBS news report is generous comparing NIF ignition to Wright brothers' flight. I would put it back further where would fliers jumped of buildings, bridges or cliffs, where the flying was actually falling; it was decades before the Wright brothers.

Prof. Charles Seife's book, Sun in a Bottle: The Strange History of Fusion and the Science of Wishful Thinking, apparently discusses the hype about fusion over the past several decades. It was certainly hyped when I studied it 40+ years ago.

https://en.wikipedia.org/wiki/Wright_brothers
In 1799, Cayley set forth the concept of the modern aeroplane as a fixed-wing flying machine with separate systems for lift, propulsion, and control.
https://en.wikipedia.org/wiki/George_Cayley
https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/historyofflight.html
https://en.wikipedia.org/wiki/List_of_firsts_in_aviation#Heavier_than_air_(aerodynes)

First manned glider flight: was made by an unnamed boy in an uncontrolled glider launched by George Cayley in 1853.
First confirmed manned powered flight: was made by Clément Ader in an uncontrolled monoplane of his own design, in 1890.

First controlled, sustained flight in a powered airplane: was made by Orville Wright in the Wright Flyer on December 17, 1903, during which they travelled 37 m (120 ft).

Flying is much easier than nuclear fusion.