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

[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.