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Comment by detritus | Hacker News Reader

This seems.. too good to be true?

I don't have the Physics chops to untangle the likelihood of this tech and the credibility of the process and its authors, so I'm hoping the HN crowd will be able to pad out the story behind this.

Certainly, from my layperson's perspective, their website isn't exactly encouraging... https://www.hb11.energy/

- ed re: last line - "books and covers, and all that"

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Check the publications page for the encouraging part. They might be wrong but they're doing real science. I've personally spoken to a fusion scientist who thought they might be on to something.

Exponential progress does sometimes have results that seem too good to be true. In this case the progress has been in picosecond lasers, which for a while have been getting ten times more powerful every three years or so.

What's great about this is it should be pretty cheap to test. The petawatt lasers only cost tens of millions in the first place, and China is finishing up a 30PW laser which they plan to let other researchers use. If Hora is right then that should be powerful enough. Even more powerful lasers are being planned elsewhere.

HB11 isn't the only company working on aneutronic fusion. The largest is TAE (formerly Tri Alpha), with about $700 million invested. There's also Helion and LPP.

Thanks to yourself and randallsquared below for your responses - I'd since posting read the following Abstract by the authors, which hinted that the underlying science was viable: https://www.cambridge.org/core/journals/laser-and-particle-b... , however my only awareness of existing 'laser fusion facilities' was the American National Ignition Facility (https://en.wikipedia.org/wiki/National_Ignition_Facility) , which I think I'd always written off as a covert testing facility for weapons that skirted Nuclear Testing limitation treaties.

The science is difficult for a layperson (such as myself) to pick apart, but the above-mentioned publications page[0] links directly to at least one paper[1] which contains some promising detail.

[0] https://www.hb11.energy/news-and-publications [1] https://aca3d9dd-3b9c-446b-8797-0ba1cdb49ccb.filesusr.com/ug...

That purpose isn't covert, it is funded by the National Nuclear Security Administration(NNSA) under the Stockpile Stewardship Program, which built the facility to mimic fusion conditions to assure the viable of the US nuclear weapon stockpile. From time to time other scientist get to use it for other fusion experimentation.

>Check the publications page for the encouraging part. They might be wrong but they're doing real science. I've personally spoken to a fusion scientist who thought they might be on to something.

I checked the publications page and so far I'm not seeing any real theory here. That doesn't mean it's wrong, but it certainly feels weird. The most in-depth equation I saw in any of their linked papers is the definition of the electromagnetic field tensor.

I'm not saying you couldn't develop a fusion reactor by doing purely experimental work with bleeding-edge laser technology. But I'd feel a lot more confident if they were to produce, for example, some kind of prediction of their net power, or a relation between e.g. laser power and fusion yield, or some other quantitative prediction about something.

For example, I'm not sure what prediction they exceeded by a factor of a billion in TFA. Shouldn't you mention that somewhere?

Another poster mention's Todd Rider's thesis, a famous barrier to creative fusion. In this particular case I think the way they evade Rider is by using higher laser powers and shorter reaction times than Rider considered to be possible. One of the important exceptions Rider acknowledges (and that I remember) is ultradense fusion; ultrafast fusion seems to be at least similar in principle.

I think the factor of a billion relates to the expectation for boron fuel with spherical compression. See for example their latest paper, page three, right column.

They do seem to be making quantitative predictions based on simulations. I don't think I've seen them boil it down to a simple scaling law though.

One of the reasons that it is difficult to predict power output exactly is not knowing exactly how much will be lost down to Bremsstrahlung, (ELectromgnetic Braking Radiation).

In any event, ultimately practical proven results will always trump whatever the current theory may suggest.

The Hydrogen Boron reaction is real and well-known to be a way to do fusion without lots of stray neutrons. The sticking point has always been that it's more difficult to cause that reaction than deuterium/tritium or deuterium/deuterium.

So the fusion here is where two protons form an alpha particle? They show a proton hitting B11 and generating two alpha particles and another proton.

1 proton + (5 protons, 6 neutrons) -> 3 * (2 protons, 2 neutrons)

https://www.hb11.energy/our-technology

The big problem with H-B11 and other heavier fusion processes is that the energy radiated away as brehmsstrahlung is greater that the energy gain from the fusion. This was worked out by Todd Rider in his 1995 PhD thesis.

Yeah, in theory it might be possible to capture the brehmsstrahlung and pump it back into the reactor with sufficiently high efficiency, but we're pretty far away from that.

That being said, all these fancy fusion reactor schemes are interesting. Just make them work on boring old D-T fuel first, then lets see if these other fuels are usable, no?

Yes, but Rider based that on various assumptions, and included an appendix on various ways those assumptions might be violated to achieve net power with aneutronic fuels. I think this reactor would qualify, since it doesn't rely on thermal heating.

Polywell claimed to circumvent it as well, I was never clear on their basis for that belief. At least Brussard seemed adamant when he was alive.

There was no basis for the belief. Read some of the comments in this reddit thread.

https://www.reddit.com/r/fusion/comments/dmqgd5/is_the_polyw...

> brehmsstrahlung

Bremsstrahlung

FTFY

Indeed, you're correct. Thanks.

Wait... Todd Rider the DRACO guy?

Yes, he moved away from fusion after basically showing the whole non-Maxwellian approach for aneutronic fusion couldn't work.

I can’t tell for sure from the article but I think they are accelerating protons with TNSA (target normal sheath acceleration). I worked in a lab in undergrad that was doing something similar, except with lithium instead of boron. The main challenges that I recall from a decade ago with TNSA are (WARNING: there almost certainly has been progress since a decade ago):

-Conversion efficiency of laser energy into ion (proton) kinetic energy

-TNSA accelerates mainly the contaminated layer on the back of targets, which may not be a big deal if you are interested in accelerating protons

-TNSA protons are not beam like. They do not have a uniform kinetic energy, and they have a wide angular divergence.

-Various laser related issues (prepulse, focal spot size/shape).

I also anticipate that it will have the same engineering problem as ICF/NIF, in that it will need to continuously replenish targets.

Here's their publications page, if you're interested in looking into it further.

https://www.hb11.energy/news-and-publications

After reading the article and skimming some of the innumberable references (the article is all references) it seems like the unobtanium part of using laser pondermotive force to accelerate blocks high density plasma from solid state is that the laser "contrast ratio" has to be very high. In the paper it cites many failed replication efforts to use this particular laser pondermotive force due to lack of "contrast ratio".

I have no idea what "contrast ratio" means, it isn't defined, and isn't in the references. Does anyone know what "contrast ratio" means in terms of high power pulsed lasers?

edit: To answer my own question, ref: https://cdn.intechweb.org/pdfs/24813.pdf

> the laser pulse contrast ratio (LPCR) is a crucial parameter to take into consideration. Considering the laser pulse intensity temporal profile, the LPCR is the ratio between its maximum (peak intensity) and any fixed delay before it. A low contrast ratio can greatly modify the dynamics of energy coupling between the laser pulse and the initial target by producing a pre-plasma that can change the interaction mechanism.

It seems to be how fast the laser turns on, the rate of change of intensity.

Do a google search for "laser induced fission". Generating plasmas with CPA lasers is becoming more common, but isn't widespread yet because the technology is very new.

These plasmas can be the source for all kinds of particles and energy in particular forms, so they may have lots and lots of uses.

One person in particular is proposing to use a CPA laser to accelerate nuclear decay, to allow radioactive waste to decay faster and become less toxic more quickly.

Of course, my own concern would be that being able to induce fission with a table top laser means that the tech may eventually exist to create a fission or fusion bomb without a nuclear trigger....

If they succeed in creating a viable p-B11 fusion power plant and that gets developed into a bomb, wouldn't it be a good thing in the sense that it could replace many thousands of fission-based bombs that have huge fallout risk?

I don't know. I think a really flashy website would be more concerning. This is a serviceable website that gets it's point across without consuming a gig of bandwidth on a video in the header background.

Agreed, I do not see their "budget" website as sign they lack credibility, I see it as a sign that they are focused on their work.

Yeah I've become wary of "scientific breakthrough" articles that never seem to materialize into anything.

But ITER uses huge tower cranes and trucks in the thousands of tons of material required to sustain a temperature hotter than the surface of Sol because of their fuel selection.

It seems the small player with a new approach that perhaps demands less complexity in their scaled up commercial reactor could win a commissioning contract with a lower bid during late 2020s early 2030s international bidding.

"First milestone is demonstrating the reactions, which should be easy."

And "chirped pulse laser amplification" is the recent discovery Hora says will make it possible.

As a researcher I really like 'scientific breakthrough" articles where the impact never seems to materialize. It reminds me that technology development works very differently on earth than it does in my imagination.

Breakthroughs happen everyday but the road to real impact is longer and more failure prone after you make the breakthrough than before it.

- with some exceptions

Not a physicist, but I thought it seemed fishy as well. I’m curious how they plan to sustain a reaction, since their setup didn’t seem to be useful for more than a single shot…

This reads like a type of ICF which normally has a stream of pellets being fed in after the initial pellet has reached a hot enough temperature to sustain the fusion reaction.

I don't think the goal is to sustain the reaction here... I think the goal is to make a pulsed reactor, where you start the reaction on each pellet in turn. You could imagine a laser firing at 1000 pulses per second, and firing a stream of 1000 pellets per second into the reaction vessel that each pulse hits.

Pellets could turn out to be the size of a grain of sand.

At https://www.hb11.energy/our-technology they list a number of papers they've published supporting their approach.

On ignoring the H B-11 reaction with high intensity lasers: https://www.nature.com/articles/ncomms3506

On the reaction avalanche: https://www.cambridge.org/core/journals/laser-and-particle-b...

On the conversion of alpha particles to electricity: https://www.cambridge.org/core/journals/laser-and-particle-b...

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