Is this "plasma breakeven" or overall break-even?
"While the latest experiment still required more energy in than it got out, it is the first suspected 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."
Here [1] is an excellent video by Sabine Hossenfelder about why you should not get too excited about this result.
However, Sabine misconstrues things in the opposite direction and lies through omission to the audience. For example including startup energy and not ammortizing it over runtime, or not assuming that the energy consumption of the experiments is part of the required energy consumption of the fusion reactor, or trying to construe that once you have a fusion power reaction that is burning it is still especially difficult to further create a functioning power reactor out of it.
The true hard part of fusion is the burning plasma aspect. Once you have a burning plasma, it's a heat source like any other (with a few side-effects like neutron output) and everything we know from fission power reactors (but with a much lower radiation) and fossil fuel generators applies.
She doesn't even show her calculations on how she calculates some of her Q_total examples.
[1] https://backreaction.blogspot.com/2021/10/how-close-is-nucle...
None of these plants are even attempting to have real energy breakeven and spend a ton of energy supplying experiments and unrelated support equipment. They don't even have a method of capturing energy as that's not the point as it would make it harder to test the physics. Additionally these plants have high amounts of "startup energy consumption" that is also factored in to the energy usage but would be amortized out over a long run. Trying to use the absolute power consumption of the experiment as if that's where the state of the art is at for true energy break even is completely wrong.
Plasma breakeven is all anyone is really working on. Once you have plasma breakeven you have a self-sustaining heater basically, which then can be used to create energy. The point of an "ignited plasma" is that it's self-sustaining and just pumps out heat, even if most of the energy is used to keep the reaction going.
Who gave you that impression? They were lying. The goal of ITER has always been to study burning plasmas and experiment with solutions to problems that a reactor-grade MCF machine faces.
"Most fusion reactions release at least some of their energy in a form that cannot be captured within the plasma, so a system at Q = 1 will cool without external heating. With typical fuels, self-heating in fusion reactors is not expected to match the external sources until at least Q = 5"
And btw, you really want more than 5, 10 or 20 ideally, but again, that's not too hard as compared to how far we've come and new reactors will be beyond that soon.
This is dead wrong. First of all, the experiment described here is ICF, in which you have to constantly re-heat new pellets of fuel. Even for MCF, you have to spend inordinate amounts of energy just containing the million kelvins plasma with few kelvin superconducting magnets, and to constantly deliver new D+T into the plasma.
If containment fails at any time for any amount of time, your reactor is instantly obliterated.
Not to mention, your source of heat only heats up by about half of the energy - the other half is radiated away as hard to capture neutrons, which are almost entirely a waste product.
I have no idea why you think that ignited plasma is enough to maintain an energy-producing reactor.
Edit: million kelvins should have been billion kelvins...
I thought the neutrons were supposed to take away the heat, to be absorbed in layers of water?
Unfortunately, I believe that the area of actually capturing the energy of the fusion reaction is almost entirely unstudied yet in practice.
It's worth noting that NIF was not intended to generate power and is not representative of a potential power plant. The lasers on NIF are old and were chosen to have a lower efficiency for cost reasons. In addition, while NIF could generate much more energy, NIF isn't necessarily going to pursue this because the higher output energy may render the machine inoperable for too long.
Dealing with a high rate of explosions is one thing this class of fusion will need to solve before being able to generate power.
[1] https://en.wikipedia.org/wiki/National_Ignition_Facility#NIF...
Nuclear weapons, more specifically stockpile stewardship (what happens as weapons age) and verification of weapons codes/simulation software (can we make new weapons without full-scale testing).
Everything else is gravy. There's a reason it's at one of the weapons labs (vs. the unclassified work done at most other national laboratories).
That's not how ICF works. Plasma, being a gas-like state, will always expand to fill whatever volume is presented. With ignition, the rate of expansion is essentially lower than the rate of fusion, allowing you to fuse all of the fuel before the plasma dissipates and cools down.
In ICF as studied at NIF, you start with an extremely precisely machined piece of metal called a hohlraum, you put a solid pellet of fuel inside at an extremely precise location, then fire a laser with extremely precise alignment to heat the hohlraum until it generates X-Rays that heat the pellet just right so that its outer layer explodes, creating an equal implosion, generating two shockwaves inside the pellet; if the two shockwaves meet just right, at the center of their meeting place you get a fusion reaction, and you hope that that fusion reaction has enough time to heat up and cause more fusion reactions before the initial implosion loses speed and expansion happens.
That initial shock is the only thing containing the plasma - once it has lost its velocity, the plasma dissipates and cools down. If ignition was reached, the gas that cools down and dissipates should be 100% He, instead of a mix of He, D and T. However, there is no way to stop this dissipation, it is a fundamental part of ICF.
The only way to keep an ICF reactor going is to shoot one laser burst at one pellet, capture the energy of the fusion, and use that to power the next laser burst fired at the next pellet.
Of course, after each burst of laser heating the hohlraum so much that it radiates the heat as X rays, and then briefly containing a 1-10M kelvin burst of hot plasma, plus a neutron bombardment, the hohlraum is destroyed. Since machining the hohlraum to the precise shape required to achieve the shockwaves discussed above is never going to be a cheap process, it is impossible to imagine ICF would ever be even a tiny bit close to economical, even if it could in principle output more energy than it requires as input.
As such, ICF is strictly a scientific pursuit, mostly interesting for nuclear weapons research.
Making equipment that can handle 1 ton of TNT exploding every 20 seconds is an interesting engineering challenge.
[0]https://royalsocietypublishing.org/doi/10.1098/rsta.2020.005...
It also considers the price of a fusion power plant to be less than that of a fission power plant, based entirely on the observation that it would have less stringent safety requirements.
Overall this article may be right in principle if taken to refer to an arbitrarily far away future (hundreds of years away at least, if ITER and DEMO are to be taken as realistic examples of the pace of improvement of fusion power in general, even if they are MCF instead of ICF).
https://www.reddit.com/r/fusion/comments/ja879n/nuclear_fusi...
"The pace of improvement in energy output has been rapid, suggesting we may soon reach more energy milestones, such as exceeding the energy input from the lasers used to kick-start the process."