Do It Yourself Nuclear Fusion

By far the coolest projects we see are those dealing with high voltages and deep vacuums. Vacuum tubes of all types fall into this category, as do the electron microscopes we see from time to time. The king of all vacuum and electron hacks is the Farnsworth Fusor, a machine that will both transmute the elements and bathe you in neutrons. Fun stuff, and [Daniel] has a great tutorial for building your own.

[Dan]‘s fusor is surprisingly simple to make. Obviously, the most important part is the vacuum chamber which in this build is based around a glass oil cup cylinder. With just a few roughly machined parts – the only tool needed to make the metal plates is a drill press – it can hold a low enough vacuum to contain a star in a jar.

For reasons of safety and sanity, [Dan] isn’t running his fusor at a high enough voltage to actually fuse deuterium into helium. This is really just a beautiful, glowey demonstration of what can be done with enough knowledge, the skills, and a handful of parts.

59 thoughts on “Do It Yourself Nuclear Fusion

  1. The problem with the design is if you make the grid dense enough to contain an actual fusion reaction, the charged field won’t allow enough gas through the grid to sustain the reaction.

    Unfortunately nobody with the big bucks (huge government grants) has bothered to R&D the Fusor to see if that can be overcome.

    Then there’s the problem with every fusion reactor design to date, once it does pass the break even point, how can the output power be converted to usable electricity?

    There’s also being able to sustain a fusion reaction for more than a fraction of a second…. oh, waitaminit. The Joint European Torus (JET) has managed to keep it together for up to five whole seconds.

    The fusion reaction has the potential to produce much more energy than should be required to smash the fuel together, but collecting and applying that much energy to start the reaction and keep it going is a bit of a problem. Once one is built that actually works in a practical fashion, the energy to run fusion reactors would come from other fusion reactors.

    User’s Guide to Operating a Fusion Reactor.
    Step 1. Plug the power cord into an operating Fusion Reactor.
    Step 2. If you do not already have an operating Fusion Reactor, plug the power cord into Niagra Falls *and* Hoover Dam.

    It’s NOT “perpetual motion”. Fuel is consumed and the energy output above the amount input is (will be) extracted from the fuel.

    Same deal with Thermal Depolymerization. The products produced from the waste contain more energy than is used to extract and convert them from the waste material. That energy is already in the material, just in an inconvenient to use form.

    1. To think that humanity can’t equal what a cloud of dust can manage to do. Some people think we’re so special too. More like special needs.

      1. Considering that due to the lack of sun like pressure we need temperatures ten times hotter than the centre of the sun in a tokamak I’d say we’re doing splendidly.

      2. I get your point, and agree that the human race badly needs to embrace humility, but…

        Our species, 10,000s of years old, has not yet had time to do what a cloud of dust can do in a BILLION years, but not much less. I’d wager we’ll be able to do it in 100 years more, when a cloud of dust/gas would STILL be about a billion years from getting it done

      3. It’s a very big cloud, to be fair on humanity. Even fusing a few atoms is more than the Universe could do with such a small amount of stuff.

    2. I think it’s fairly safe to say there’s been sufficient research into fusors and other similar devices to see that it’s unlikely that it’ll ever be able to scale up sufficiently. Rider’s Fundamental limitations on fusion systems not in equilibrium,

      Honestly, projects like this make me really happy. A really simple fusor! How fantastic!

    3. Ok, the first person to make a working fusion reactor that produces more energy that it consumes, runs in this state long term and can be used to replace present energy will get a free cookie! Get to work.

    1. it works as a neutron source and i bet you could learn a thing otr two about charged plasmas if you really wanted to observe and experiment.

      a laser engraver is nothing but a light show till you stock up on material.

  2. So how safe is this? They’ve plastered warnings all over the make instructions about generating x-rays, gamma rays, and free neutrons, but it sounds like this isn’t powerful enough to actually produce free neutrons?

    Is this too dangerous to leave running in my office as a pretty light show?

    1. Xrays can be produced at voltages as low as 5kv. Not a great idea for a light show. Though you can probably make it light up at just a couple kv at a few mA so it might be possible.

      1. Attenuation lenght for soft x-rays, using such a small device, is too short to be of any concern. You should measure x-ray emmision of your average japanesse widescreen crt TV, leaded glass my ass xDDD

  3. what really pisses me about fusion is they still talk about using waste heat, to boil water, to make steam, to turn a friggen turbine!!!!

    Plasma by definition IS a super conductor!

    1. What’s your point? Superconductors conduct electricity without resistance, which is crazy useful, but doesn’t magically produce energy. Unless you’re fusing Helium 3 you need some way to use the reaction to generate electricity, and transfer of heat is the simplest currently known way to do that.

      1. my “point” was that if you have a moving super conductor then it’s got a magnetic field, so if you have it moving past some stationary coils it’ll generate current.

        1. 1/. I don’t think plasmas are superconducting!
          2/. Simply because the plasma is moving doesn’t mean a current is generated. The plasma would have to cut through the lines of magnetic flux to produce a current. If the plasma just circulates then no lines of flux are cut.

    2. A lot of people think “why still use a turbine?”

      It’s because we have 130 years of engineering knowhow applied to making them the most efficient way to convert heat to work. While the ideal Rankine cycle (steam turbine cycle) isn’t as efficient as the ideal Carnot cycle, engineering considerations make it the best approach for industrial use.

      Efficiencies for the photoelectric effect and for straight up “grabbing” loose high-energy electrons are abysmal compared to the current turbine efficiencies. They’re so bad that a cogeneration solution applied to a coal/ natural gas power generation facility recovers about as many percentage points of energy as they’d make in total.

      The way the plasma is contained in a fusor eliminates the possibility of generating current by coil excitation like you suggest.

      There’s a great google talk done by Robert Brussard about his work on this type of fusor: http://www.youtube.com/watch?v=rk6z1vP4Eo8

      In any case, the current research trend *is* in getting away from steam generation– dozens of research groups are studying organic PV and are getting great results, and there’s about as many approaches being considered as there are elements on the Periodic Table.

      Both you and the scientific community are pissed at steam turbines. Hopefully something cool will come out of the research!

      1. I just think any of the torus designs should be able to get better conversion.

        Any idea how this idea could get useful “work” done?

        I keep reading about them, but don’t see how they can

        1. IIRC, the idea is to use a thermal blanket to generate steam.
          Part of the problems with toroids is that containing a plasma fluid stream is insanely energy expensive and if there is any failure of the containment device, you get jet of plasma (which has been significantly accelerated) slamming the torus wall.
          The way this fusor design works is by essentially making an energy “well” where every direction from the center looks like “uphill” from the deutirium’s point of view. Since it’s a sink, it’s inherently stable, but Galane points out above that it’s currently impossible to reach self-sustainment with the fusor design.

    3. Super conductors are cool and all but they don’t just produce energy that can mysteriously be used to power things. We still need to convert it to something usable. Most of the resultant usable energy from a fission reaction is heat, lots and lots of heat. To keep it from melting down you need to cool it down and oh look now we have to do something with the heat. Its just convenient that we convert the heat to electricity via a turbine. I think the biggest issue with the Farnsworth design is the lack of planned cooling in the event of a sustained reaction.

    1. This design doesn’t. In fact, getting neutron emission is pretty tough and is a significant achievement in the amateur fusor community.

  4. This month’s Make magazine has Dan’s article on page 90. Just FYI in case anyone is interested in the print version.

  5. Couple of questions:
    1. once a vacuum is established, do you still need the pump?
    2. Could you leave it on for extended period of time? I envision building this as a decorative piece in my office.
    3. Is it loud?

    1. 1. Probably. Unless you can create a design that is leak proof which will be pretty tough. Then you have to deal with outgassing so it really needs to be baked out before being sealed off. A lot tougher project to do than something like a plasma globe.

      2. Maybe. Sometimes you will create electron beams that can cause localized spot heating of the glass which will cause it to crack and implode.

      3. Other than the vacuum pump, no.

  6. maybe someone can solve the lithium shortage or at least the cost by making their own by reacting helium to make lithium.

    same goes for making helium from hydrogen and solve the helium shortage.

        1. well i am a real amateur in a lot of way’s :-), maybe i should have taken some more words to expain but Okian Warrior now did this below. my point is that there are (a lot) working plasma and even neutron producing fusor projects on the web, why link to this?

    1. This is not a working fusor.

      The vacuum pump specified in the build will pull to 25 microns, which is .025 Torr. One Torr is the pressure needed to push a column of Mercury up by 1 mm, so this is equivalent to a pressure of .025 mm of Mercury.

      At that pressure, the mean free path is about 10 mm (about 1/2 an inch). That means that any particle flying around will encounter another particle on average every 10 mm.

      No particles in the fusor are completing the path into the center of the chamber to be fused. They are being bounced around and emitting a plasma glow, but there is no fusion going on.

      http://www.ytionline.com/techinfo/molecularpath.html

      A path length of 70 mm (2.7 inches) might be long enough for a project of this size, that would require 1 micron, or .001 Torr. You can’t get that with a conventional pump (at least, not easily) so you need both a conventional pump to get to 25 microns and a diffusion pump to go the rest of the way.

      This assumes that your pump can actually pull to 25 microns, however. A very good pump will do this when new, most pumps won’t get that far (but will get to 100 microns, which is still good enough if you have a diffusion pump).

      The gauge specified in the project is a) inaccurate (I’ve got one) and b) too coarse of resolution to tell whether the chamber vacuum is in range. You cannot accurately measure vacuum at that level with a mechanical gauge, you need a different technology, such as a pirani gauge or similar. (You can sometimes find used Pirani gauges on eBay for cheap.)

      Let’s not forget that the project has no way of injecting Hydrogen into the chamber, let alone Deuterium. The system as-built is attempting to fuse Nitrogen.

      So in reality the project is an expensive neon sign. The purple’ish glow is probably plasma discharge from leftover atmospheric nitrogen in the chamber.

      The project, according to the description “generates only insignificant quantities of fusion products”.

      I strongly suspect that “insignificant quantities” is actually “none”.

  7. I’ve been looking into building one of these, the snag here is a non working (seized) vacuum pump.
    It is however possible to make your own, all you need is 80 wire HDD cable, two sheets of glass, some silicone and a driver that generates a wave drive along the sheets.
    A simple low vacuum pump such as an old refrigerator compressor run in reverse completes it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s