The Fusioneers, who build nuclear reactors in their back yards | Hacker News Reader

The Fusioneers, who build nuclear reactors in their back yards

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168 pointsFjolsvith54 comments

These are Farnswoth Fusors[1], first developed by Philo T Farnsworth, one of the inventors of television.

The devices use about 100,000x more energy than they produce FROM FUSION (edit, thanks), but some fusion does occur. An individual ion can be heated by 11,000 kelvins with a single electron volt, so 15,000ev is enough to reach fusion temperature. The statistical challenge is getting ions to collide - overcome the (repelling) coulomb force - and fuse.

There are discusson groups online for this topic [2] and there's even a high school in the Seattle area that has a fusor [3].

[1] https://en.wikipedia.org/wiki/Fusor

[2] http://www.fusor.net/board/

[3] http://www.industrytap.com/overview-polywell/31940

IMO, produces energy is a poor way of describing at this. They produce ~1,000 parts light:99,001 parts heat per 100,000 units of electricity and 1 units of fusion. In other words 100,000 units of electricity liberates 1 unit of fusion power.

https://en.wikipedia.org/wiki/Fusion_energy_gain_factor is meaningful, but it's talking about inputs not outputs.

PS: Ok, heat is a poor description. 1,000 pars light, 99,000.9 units of heat, and 0.1 unit high energy particle radiation.

Isn't that like saying a lightbulb doesn't use any energy because its output of heat and light equals the energy input? Or that I didn't use any money shopping because the cash all stayed in the economy?

Sure, a light-bulb does not destroy any energy, it uses electricity and increases Entropy. If you want to say it consumes something then a light bulb consumes the potential to create Order by transforming electricity into heat and light.

It sounds like the argument is considering what the output energy might be used for. If you want a fusion device to power your heating and lighting, then the "waste" heat and light from the device may actually be useful.

It's like replacing the radiators in your house with servers or bitcoin miners; you still pay for electricity, and it's still warming up your house, but you get compute cycles or bitcoins "for free". If the waste heat/light of a fusion device is of comparable efficiency as conventional heaters/lighting, then we're "breaking even"; if the device manages to perform any fusion, that liberated energy would be a "net positive".

Of course, a fusor doesn't seem like a particularly good idea for household heating or lighting, and that argument is completely inapplicable to things like power plants.

Not many people have turned one element into another. That alone is pretty cool.

> that argument is completely inapplicable to things like power plants

Actually, it's not unheard of for waste heat from power plants to be used as residential heating.

https://en.wikipedia.org/wiki/Cogeneration

Some of the nordic countries use local power plants to create municipal steam for heating homes, I believe.

I looked at building one a couple of years ago before deciding I couldn't afford the equipment to make sure it was safe, but I always had this in the back of my mind: Don't all nuclear reactors use heat as the main output? To drive steam generators (like a conventional plant) or solid-state devices like a peltier-based battery used in satellites?

If you put a bounding box around a Farnsworth Fusor, and put in 100W of energy, would you not get a little more than 100W output from the fusion reaction?

Obviously still not viable as self-sustaining, since 100W of electric energy in would be lower entropy than the 100W+ coming out, but it would be a method of producing some energy as long as it's fed from another source.

Obviously, using a heat pump would be a much better way of turning 100W of electricity in to >100W heat, but still, a Fusor isn't net energy negative (although it is terrible with conversion of entropy).

You are ignoring the energy in the fuel. Which is arguably a reasonable thing to do as we don't have great fusion reactors yet and H Bombs are not exactly sold at Home Depot. But, it's still the kind of fuzzy thinking that leads you to assuming bad ideas will work.

As to 100W vs. > 100W. 100.001W might as well just be 100W in just about any meaningful way. However, Jet is vastly cheaper per watt of liberated fusion energy. https://en.wikipedia.org/wiki/Joint_European_Torus

It depends what the main power output is. Neutrons from D-D or D-T (deuterium-tritium) are really hard to convert into electricity, but some types of fusion like p-B11 (hydrogen/boron) generates alpha particles that can be directly converted to electricity.

"These are Farnswoth Fusors[1], first developed by Philo T Farnsworth, one of the inventors of television."

Wow, I've been a Futurama fan since the show first came out and just now got that reference. Well done, Matt and David.

I've built a fusor[1], and in its simplified form, it's just a large, negatively charged grid in a vacuum chamber with some hydrogen sitting around. Nothing to be afraid of!

You're absolutely right that these devices don't produce net energy. I built mine because I wanted to learn more about all the tech involved (high vacuum, high voltage, some nuclear physics). They're really good teaching projects for folks going into experimental physics, since there's a neat outcome without too much danger.

I assembled a coffee table book with some pretty pictures about it, PDF copy here: http://shia.wsyntax.com/stuff/fusion/fusor_book_web.pdf

[1] http://fusion.wsyntax.com/ , http://fusion.wsyntax.com/setup/

I really enjoyed reading that, thanks!

Very interesting. Thanks for that.

How much would it cost, roughly, to manufacture helium from one of these?

From what I understand, we are running out of our natural stock.

It would cost a fuck ton! Here's how I figure it:

Each fusion event makes one He atom and releases about 17 MeV of fusion energy. Since (one mole) X (one eV) = ~100,000 Joules, fusing one mole (2 grams) of He would produce about 1.7 X 10^12 Joules. That's about 472 megawatt-hours of fusion energy produced.

Another commenter says that the energy INput (to the Farnsworth fusor) is about 100,000 times the energy OUTput; so fusing that 2 grams of He would require a 2,000 megawatt power plant to run for 23,600 hours, or 2.7 years.

Readers: please correct any mistakes you find.

> fusing one mole (2 grams) of He would produce about... 472 megawatt-hours

Or, from a different angle, that energy density is why fusion is the holy grail of energy.

Since a fusor normally runs on deuterium fuel, wouldn't the output be helium-3 with a mass of 3 grams/mole?

Not that it makes a big difference - producing helium with a fusor remains extremely impractical.

Oops! I used He's atomic number (2) instead of its atomic mass (usually 4).

I believe deuterium fusion events mostly produce He4, occasionally He3 + neutron. So we'd actually produce between 3 and 4 grams.

No, deuterium-deuterium fusion reactions usually produce helium-3 and a neutron. Due to the conservation of energy, producing helium-4 requires the emission of a gamma ray. This happens rarely because, since the strong nuclear force is stronger than the electromagnetic force at small distances, fusion reactions tend to release energy as protons and neutrons rather than gamma rays.

> Philo T Farnsworth, one of the inventors of television

The (very) old game show "I've Got A Secret" had Farnsworth on as a guest, with his invention of television as the "secret".

    Player:     "Do doctors use this object?"
    Farnsworth: "Yes, it's been used in surgery."
    Player:     "Is this some kind of machine that
                 is painful when it is used?"
    Farnsworth: "Yes, sometimes it's most painful!"

https://www.youtube.com/watch?v=pKM4MNrB25o

> These are Farnswoth Fusors, first developed by Philo T Farnsworth, one of the inventors of television.

that sounds like something straight out of a heinlein book!

I have a hack project like this going in my garage.

I'm trying to build a resonant tuned polywell device. The tldr is polywell + tesla coil power source + microwave oven = fusion? I have no idea if it will work but is something I wanted to try.

The original polywell is a steady state device, where this is meant to create a dynamic system in tune with the power source.

https://en.wikipedia.org/wiki/Polywell

http://2.bp.blogspot.com/-3BPtWiGxd3c/Vj7ecWEoXuI/AAAAAAAAGc...

How do you measure your fusion events? Does a geiger counter work?

Not the above poster, but typically people will test first with hydrogen to make sure they have good plasma characteristics and containment, then switch to deuterium and use a neutron counter to measure the 2.45 MeV neutrons that come off of the D + D -> n + He3 branch reaction.

A Geiger counter is a good idea, though. Many people don't know until they work with it that high voltages (above 30 kV or so) will cause a fair amount of X-rays from stray electrons being accelerated. So, even when you aren't actually doing fusion, just having a device turned on will cause some X-rays, and its helpful to know that your dose rate is low enough to be safe. There are some failure modes that can cause large amounts of X-rays and you'd want to be aware if that was going on.

I haven't gotten that far but this is correct. Most people in the fusor community fuse deuterium and use a neutron detector to prove fusion is happening.

Aye, you can also get additional proof by placing different thicknesses of attenuators (parrafin wax works well for this) between your neutron counter and the fusion device to demonstrate that the energy of the neutrons is commensurate with the energy from a D+D reaction.

Borax is cheap and helpful for shielding if you start getting more neutrons than is comfortable. Neutrons are a serious radiation hazard but most fusors would be happy to get into the dangerous range.

> I'm trying to build a resonant tuned polywell device. The tldr is polywell + tesla coil power source + microwave oven = fusion? I have no idea if it will work but is something I wanted to try.

I hope you thought about all the consequences this may have. See Primer.[1]

[1]https://en.wikipedia.org/wiki/Primer_(film)

excellent documentary

The sequel is a let down though. Oh well.

There's a sequel? Or did you mean Upstream Color? It's definitely quite different and more artistic. But I want to give it a second chance.

Oops! Must have gotten my timelines mixed up. Please don't tell anyone.

I'm interested in why you would want to try a resonant Polywell. Are you willing to share your thoughts on why you'd want to go that route? Regardless of whether you want to discuss it, good luck with your project.

It's a combination of ideas. I liked the idea of the polywell, but there was another project that also peaked my interest, plasma focus. One of the researchers described why their idea was better than the others, and it was quite convincing. Plasma is a dynamic system and their design works with the plasma dynamics instead of against it. This led me to the idea of a dynamic polywell, where the negative potential in the center could be tuned to oscillate. Maybe there is a sweet spot or harmonic that will cause fusion.

I have no idea if it will work, but is an interesting project and something attainable in the garage. If nothing else hopefully it will at least be a fancy plasma ball lamp.

More on focus fusion:

http://www.extremetech.com/extreme/184280-focus-fusion-has-c...

Here are some of my pics (sorry couldn't edit the original post after work):

http://imgur.com/a/Tsg40

that's awesome! this would be a sort of dream project for me (I am not classically trained in physics; just a computer scientist)

I definitely encourage you to try out your ideas. I'm a software engineer by day myself and dropped out of college. It seems like a crazy idea to me but, why not? I try to not live with regrets. I think that when I'm on my death bed, I would regret never trying my ideas out.

Impressive people, but I don't feel that I got a sense of what they were actually doing. I understand that it's a challenge for a writer who probably doesn't understand the subject well, to talk to the average read who doesn't understand it at all. Still, this feels like a wasted opportunity to teach, and to inform others with more knowledge about what these interesting people are doing.

bingo. I have no idea what they were building based on that article. The first "quote" about uranium was especially misleading.

Felt like we read just the beginning to a very thorough article. Instead we just got introduced...

This feels like the introduction to a book. It sounds like an interesting one.

This listing won't be full without David Hahn aka "Nuclear Boy Scout". https://en.wikipedia.org/wiki/David_Hahn

Wow totally forgot about this. Wiki linked to an article about what he's been up to recently: http://www.dailymail.co.uk/news/article-2506549/Uh-oh-Radioa...

He's been through a lot but still has a hunger for learning.

Hahn was working with fission not fusion , he was not a 'fusioneer' but splitting the atom.

Hahn produced amazing amateur nuclear work nonetheless, ( somewhat out of control when his reactor went critical ).

I wonder if you could use a Farnswoth Fusor as a neutron source to do some fissioning?

yes you can, and it means you can have a reactor which (when the power to the fusor fails), it turns off(ish).

I read his story a while back and was shocked that I used live nearby and may have (as a paperboy) delivered newspapers to his house. I left the area a few years before his experiments, though.

Lockheed-Martin's Skunk Works is trying to build a useful fusion reactor using a somewhat similar approach.[1] They announced this a few years ago, and last fall, their people gave a talk at the Princeton Plasma Physics Laboratory. (There's video, but it won't play in Firefox on Linux.[2])

It's striking that a very capable organization is working on this.

[1] http://www.pppl.gov/events/colloquium-lockheed-martin-compac... [2] https://mediacentral.princeton.edu/media/Thursday+Colloquium...

Nice bios. Would rather read about what they're building.

Farnseworth Fusors it sounds like. So EIC fusion, fortunately it's pretty tough to get a strong enough vacuum and proper backfill of deuterium to produce actual fusion which would stream neutrons out and actually be dangerous beyond the dangers of dealing with high voltage, high pressure, and x-rays. They do usually ionize the gas in the confined center which looks pretty cool.

Exactly - this was just the opening page to the article I would have like to have read; that may be because I did my apprenticeship in the UK Atomic industry and long for my 20s, but maybe it's because it would be really interesting to read about this stuff - I had no idea people were doing this sort of thing as a hobby. I feel an evening's search-and-read activity coming on!

Let's not forget Doug Coulter:

http://sploid.gizmodo.com/this-chain-smoking-gun-loving-guy-...

He has a forum dedicated to all kinds of stuff. He occasionally stopped by Schneier's blog to deliver insightful posts. I particularly liked his calling out the Anarchist Cookbook's many ways of killing people... that try to do what it says. ;)

While we're at it, are safety considerations the only problem that prevented nuclear powered automotive engines? I've always wondered why.

Mostly its about size. There is effectively a minimum viable size for a fission reactor. There are a pinch more than 2 neutrons born from each fission event. In order to operate at criticality, exactly one of them must go on to produce another fission. Leakage of neutron radiation from the effective surface of the core is a major way that neutrons don't make it to cause another fission event. As the ratio of surface area to volume goes up (because the core got smaller) it becomes harder and harder to design a core that doesn't lose neutrons to the other loss mechanisms to keep up with the increasing loss out the core's surface.

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