Step 6: Setup Neutron Detection

The proof of fusion (and a quantitative analysis of how much fusion) is obtained through detecting neutron radiation, the byproduct of a D-D fusion reaction. There are three options which will be described. They are in order of descending ease of setup.

-A Neutron Bubble Dosimeter
A bubble dosimeter is a small unit with a gel in it that forms bubbles when ionized by neutron radiation. This is the easiest form of neutron detection available since all you have to do is unscrew the top and set it next to the fusor. Some of the drawbacks are that it is an integrative detector which means all you get is a total neutron emission number over the time that it was used, rather than an instantaneous neutron rate. Additionally, they are somewhat hard to get since the only company to make them is Bubbletech in Canada, which has a minimum order of 3 with steep shipping and handling (expect to spend $700+ if ordering directly from them not in a group buy). Additionally, they tend to be fairly worn out after a year of shelf life (although I've kept mine in a refrigerated storage container at 50*F and it seems to be like new after I think more than a year). The advantage is that calibration data is provided with purchase and of course it is easy.

-Silver Activation
When silver is placed near the reactor (with a moderator [paraffin wax, water, HDPE, etc] between it and the neutron source, since only thermal neutrons will activate the material) it becomes slightly radioactive with decent neutron fluxes. It has a short half life of only a few minutes, but if you quickly put a geiger counter next to the silver, counts can be detected. In my best runs, I have gotten a piece of silver to about 250CPM over background on a CDV-700 geiger-counter. The disadvantages of this are that it requires a decent neutron flux (at least about 100,000 neutrons/s) which is above the average "beginner's first run" neutron rate. Also, it is somewhat difficult to calibrate, and the counts can't be taken until after the fusor has been shut off.

-A Proportional Tube
Tubes can be purchased which are filled with either BF3 or Helium-3 (some very old tubes are Boron-10 lined inert gas tubes). These tubes, similar to a geiger counter, can be used with a counting device to detect electrical pulses when neutrons pass through the tube. Either an all-in-one counter can be used, often made by a company called Ludlum, or a modular counting system can be made using NIM modules. The tube is surrounded by about 2 inches of moderating material such as wax or water. This is by far the most accurate and useful form of neutron detection, however the cost of a new tube is prohibitive to most people, and they are extremely rare on the surplus market. Also, counting equipment can become quite costly.

NIM Configuration: If you chose to make a NIM setup as I have, the typical layout is a charge sensitive pre-amplifier at the head of the proportional tube, which is plugged into both a high voltage power supply generating positive polarity voltage appropriate for the tube (in the range of 800V-2kV generally). The amplifier also hooks into a shaping amplifier, which is followed by a Single Channel Analyzer (for setting the detection discrimination level), followed by a pulse counter and/or rate meter.

Shown in the first picture is my NIM setup, the second picture is the pre-amplifier attached to a moderated helium-3 tube, the third picture is a bubble detector after being exposed to neutrons.
<p>Alot of comments unanswered here: </p><p>1.No machine will ever be 100% efficient. We can get closer and closer, but never to exactly 100%, because some energy will always be lost as heat.<br>2. Energy in &gt; Energy out. (look up gibbs free energy for more info). Since 100% efficiency is impossible, you will never get exactly, or more energy out of a reaction in you put in.<br>3. While im sure that this machine can produce small amounts of fusion reactions, almost all energy is lost to heat or radiation, don't plan on dumping a few thousand bucks into building one of these and having near perfect clean energy.</p><p>4. Basic nuclear chemistry. This machine uses incredibly high temperatures to overcome the positive to positive repulsion between deuterium nuclei. No, this will not work with H-1, H-3, or an radio-isotope of thorium. Only deuterium (an isotope of hydrogen with an atomic mass number of 2 AMUs.)</p>
Can I use hydrogen instead of deuterium?
<p>What's with all these people saying that you can't make a machine produce more power than you put in it? For example, you could theoretically power an oil pump with the oil if you did the fuel right, and still have extra. Isn't this about harvesting power? In this case from a nuclear reaction? Please correct me if I'm wrong</p>
That's called perpetual energy and is impossible, though I can understand how you might think this. In your example you propose to power an oil pump with the oil it retrieves. You couldn't do this because energy will be lost along the way in the form of heat through friction. At the end you would be left with less energy then when you started. The same is true for this fusion reactor. The reactor converts the dutrium (spelling?) into energy but the wrong kind. To be efficient it needs to convert the energy into electricity instead of light and radiation which is the case.
<p>Energy can't be lost or gained but can be converted into different forms. Oil is a form of matter that can release energy when converted. Oil is converted into usable energy through combustion and is converted into an unusable form. A fusion reactor consumes energy to fuse atoms together and release the energy in them. It produces more energy than nuclear fission but costs more as well.</p>
Ho much does thos cost
<p>I am really interested in this and would love to build it. Is it possible to hook this up with thorium instead of deuterium? How can I simplify this project? Is this fusion reactor hooked up to a capacitor or something of the like that it charges - how is the power harnessed?</p><p>Thanks,</p><p>Josh</p>
<p>How is the power harnessed?</p><p>The most likely way you would harness the power would be to use the heat coming off the reactor to drive a thermal process, probably with water becoming superheated steam to turn a generator turbine.</p>
<p>There is no power harnessed. You lose practically everything to radiation.</p>
<p> Can you please explain what's the point? I don't think the efficiency of all this is 100%. So aren't we just using a lot of voltage to produce less voltage?</p>
<p>The points for building this sort of thing have already been described, I believe. If you would like to have a neutron source, then this could be a path to having one. Then, again, for most folk, the point would be merely to have built it and to have seen it working, and to consume extra time and money that you have. The second question you ask rather answers itself, I think.</p>
Is it even theoretically possible to get more energy output than input? I'm not goading, I'm really asking. I would've thought that energy can be transformed into other KINDS of energy (i.e. fossil fuel into electricity) but the amount of energy would be equal at best. Assuming energy is subject to the rules of the game, where/how would energy that did not exist be produced? Where would it come from? I've always thought of energy as 'static' in the sense that x units of energy = x units of energy. The bottom line being you can't make something where there was nothing. Am I waaaay off in ignoramus territory here? I'm not as well read in physics as I should be, so constructive criticism and education is more than welcome.
<p>Yes. X units of energy = X units of energy, but X can't be used as fuel. So we convert it into Y units of energy, which is the same amount of energy, but in a different form that can be used by us. Nuclear fusion has no practical use as a fuel source since it costs more power to fuse atoms than its energy output from the energy release of the atoms. Although it is a cool project to make just for fun</p>
Yes it is possible to get more energy out than in, if it wasnt then we wouldnt exist because things LIKE STARS wouldnt be emitting radiation in the forms of light and heat. But its not likely in this setup. This is more of a &quot;man can artificially create the same reaction that fuels the stars&quot; kind of thing
Hit the reply button too soon. The point of this is really just novelty and to peak interest in physicists to be, and to do real alchemy. Please google fusion before commenting, though. All of your questions and observations are adressed within the first 5 results of a search for &quot;fusion&quot; I promise.
<p>Theoretically possible, but practically very difficult. Its been nearly a hundred years of well funded research and they have only just managed to do an experiment with more energy out than put in. <a href="http://www.bbc.co.uk/news/science-environment-24429621" rel="nofollow">http://www.bbc.co.uk/news/science-environment-2442...</a> and this very far from producing a self sustaining reaction, which may take another 50 years of research. <br><br>Power generation is not the aim of this project. You would need a much more involved set up to even try.</p>
<p>Just to add to that answer, there is a good change we will see some fusion reactors in controlled (ie &quot;non-commercial&quot;) settings producing a reasonable amount of power output in the next two decades. In fact, many tokamak designs already produce sustained reactions of several seconds... which may not sound like much but is long enough to use iterative techniques to squash bugs and design a long term use reactor, and long enough to have positive power out.</p><p>As for where the energy comes from, it's from mass-energy conversion. When the elements lighter than iron fuse nuclei, the product element is usually of a slightly smaller &quot;atomic mass&quot;. If you're wondering how that works (because wait, don't we still have the same number of protons and neutrons?), you can either accept some hand waving or go take some advanced physics, but the outcome is that we loose a little mass and gain energy. Since that energy scales with the mass times the speed of light squared, that second part is really big so the first part can still be kind of small and produce energy output. That is to say, our output from fusion is common elements (and the inputs are not particularly rare), and we don't need a lot of material to get a LOT of energy. </p><p>Right now, however, we end up using a lot of energy overcoming repulsive forces between nuclei. We do that by raising the temperature to a point where the mean velocity of the (now plasmafied) atoms is high enough to keep going even against the very high forces applied by short range electric fields at the nucleus of an atom. Since energy tends to go out into a cooler space (all of earth), the current difficulty is keeping that temperature high enough, or finding another way to overcome atomic forces keeping things seperated. </p>
<p>lockeed martin says they'll have it done by 2026</p>
<p>And it'll fit &quot;on the back of a truck&quot; Is that a Semi truck or my neighbor's F150 extended cab? </p><p><a href="https://en.wikipedia.org/wiki/High_beta_fusion_reactor" rel="nofollow">https://en.wikipedia.org/wiki/High_beta_fusion_rea...</a></p>
<p>Oh wait: The project estimates that it could weigh 300-1000 tons.</p><p>Should have read the article. Sorry. </p>
<p>I don't know, it can't be the same one here on 'Instructables.' If so, I think they made a mistake; I think it should say 300-1000 lbs, not tons, but you can make one under 300lbs. It will easily fit in the bed of an f-150, especially if you keep that in mind while you're making it, but what's the point? OK, I just saw the link and your other comment; you meant the one Lockheed is making that will have a net positive output power ratio. Yea, not fitting on a truck any time soon. I don't think that one has even started to be developed yet, first they need to get the fusion right before they can make a compact model. Here's the Lockheed website for their compact fusion version:</p><p><a href="http://www.lockheedmartin.com/us/products/compact-fusion.html" rel="nofollow">http://www.lockheedmartin.com/us/products/compact-...</a></p><p>And here's a little known company that says they'll have it done before Lockheed-Martin; may be a company worth investing in:</p><p><a href="http://www.technologyreview.com/news/414559/a-new-approach-to-fusion/" rel="nofollow">http://www.technologyreview.com/news/414559/a-new-...</a></p><p>Of course you probably know the articles people are posting here, that say, &quot;nobody has yet produced more energy from fusion reaction experiments <br>than was required to conduct the experiments in the first place,&quot; are wrong. That turned out to be false shortly after the articles were published last year; it has been done since then, pick a link, choose one:</p><p><a href="http://www.ryot.org/scientists-california-make-nuclear-fusion-breakthrough/407669" rel="nofollow">http://www.ryot.org/scientists-california-make-nuc...</a></p><p><a href="http://www.bbc.com/news/science-environment-24429621" rel="nofollow">http://www.bbc.com/news/science-environment-244296...</a></p><p>That reminds me- Why don't you have anything to drink? Choose one, making you better feeling:</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/XEQ62baVQ3c" width="500"></iframe></p>
<p>No, no you're making good observations, and moreover you're correct! While energy is not &quot;static&quot; in the sense that energy can become mass (e.g. the big bang) and mass can become energy (e.g. solar fusion or black holes) by the equation we know as E = mc^2 + [other things nobody cares about], it IS in fact conserved in a fusion reaction. &quot;eV&quot; is a unit of energy, but it's also a unit of mass for small particles, so let's just equate mass and energy for this oversimplified explanation: particles like protons and neutrons have specific &quot;resting&quot; energies (i.e. when they have not been excited). However, when they combine to form a nucleus, there is a binding energy that means that the final nucleus has LESS energy than the individual particles did before! Mathematically, you still have x = x, but it looks more like (y+z) + (y+z) + energy =&gt; 2y + 2z where 2y is the final energy of the new nucleus, and 2z is radiated energy--much greater than the initial activation energy. Thus it would appear that more energy is created than applied, when in reality, you're just helping the system reach a lower energy level, thus giving off more external radiation. (Think of it like pushing a box up a hill 10 feet then letting it slide down the other side 20 feet. It takes x amount of energy to push it up, but y &gt; x energy comes out because gravitational potential energy is converted into mechanical energy (then friction and heat). There is an activation energy for fusion, but because the free particles move to a lower energy state, like the box, they will give off more energy and make it worthwhile.) </p>
<p>as far as energy forming more than its original amount it is very likely. Imagine multiple explosions timed at the right time one building off of the other to form a new KIND of energy not amount. This is probably how the concept of the atom bomb was theorized. See what we are missing is not all energy is the same type of energy therefore all energy cant be lumped into one category.</p>
<p>As far as I know the conservation of energy law still holds, so, no you can't get more energy out of a process than is put in. As I'm sure you know, though, there's an awful lot (E=MC^2) of energy to be had from a small amount of matter. Difficulty is damping a fission reaction or sustaining (and containing) a fusion reaction.</p>
Conservation of energy- that's the one I had in mind, thank you. Yes, I understand that the challenge is to efficiently unlock the energy in one thing to use in whichever way... They say one mega-thunderstorm can power the U.S. for however many days, but how to harness it? I suppose for that matter that a mountain has a vast amount of potential energy, but good luck trying to get a mountain to power your toaster. NOW, confusingly, someone else replied that YES, it is theoretically possible to get more energy out than you put in... But as you say, and I'm inclined to agree, that seems to violate the laws of physics. The energy cannot just 'appear' where it previously didn't exist, no? It would be amazing to harness the energy in a grain of sand and use it to run a car, no question. But to my thinking, (which may be flawed,I'm open to that) the very best result you can hope for is that you convert every last drop of energy in the grain of sand to an exactly equal amount of energy in the form of electricity let's say. If each grain of sand has a calculable amount of energy, and I convert that energy into another form of energy- where would 'more' energy come from? It cannot physically be.
I just had a thought: I'm thinking maybe what people mean when they say &quot;more than you put in&quot; they mean getting more electrical power output than input... That completely ignores the source of energy that you're using the electrical input to unleash. If I use 100 tons of coal to produce enough electricity to power a machine that unlocks the energy in hydrogen atoms, and I do it effectively enough to get back the equivalent of 200 tons of coal's worth of electricity, I did NOT get back more energy than I put in. I tapped into the energy of the hydrogen atoms to get that output. I'd much rather use hydrogen than coal, so that's a win- but I only changed the form of the energy, I didn't get more out than I put in.
<p>Yes, you're right. Pretty much uniquely to fusion discussions, when people talk of &quot;getting more energy out than put in&quot; they are discounting the energy in the actual fuel ... If they're not the refer them to Scottie: http://youtu.be/nfZ12UGiisM</p>
<p>were it possible to produce more energy output than input series of the devices would be installed on every power grid in the world. They are not. That should logically answer your question</p>
Energy is produced when atoms fuse together, it's the reason our sun produces energy.
<p>You could argue that the point is neutrons out. You could also argue that the point is &quot;because I can&quot;. </p>
<p>Ultimately the idea would eventually be to use a fusion reactor to <em>produce</em> more power than it requires to run, but that's not what it's capable of right now.</p><p>Why bother doing this at all?</p><p>Even if it's not producing more power than it takes in, it still has its uses. I don't know about how useful it would be for home projects, but it does make a powerful neutron source for various kinds of analysis.</p><p>For examples of neutron spectroscopy, see <a href="http://www.isis.stfc.ac.uk/instruments/neutron-spectroscopy4761.html" rel="nofollow">http://www.isis.stfc.ac.uk/instruments/neutron-spe...</a></p>
&quot;Produce more power than it takes to run&quot;. That's a perfect, succinct way to say it. That is critically different than 'more energy out than in'.
<p>In this design power isn't harnessed. Even if you could capture 100% of the expelled radiation, the unstable nature of the fusion reaction in this environment (the high voltage is essentially restarting the reaction over and over) makes it so this is a net loss system. </p>
<p>Josh, I suggest you read up on, fusion and maybe physics in general. I'm not trying to be a dick here but your comment sounds as if the you heard the words 'thorium' and 'fusion' in from sort of pseudo-science article and think devices like these are plug-and-play free energy. <br>Thorium is a solid fuel for nuclear fission (actually the exact opposite of fusion). I do not recommend attempting fission at home because of obvious nuclear hazards (although I doubt you'll get anywhere before either contaminating yourself or get arrested). Deuterium is a isotope of hydrogen and it's a gas. Now in fission you try to split a heavy atom (uranium, thorium) and try to start a chain reaction which you then try to contain. The produced heat is used to drive a turbine. In fusion however you try to fuse two light atoms, which also releases energy. Although the process of fusion is not that difficult as the above article shows, having enough fusion reactions to cancel out your losses and harnessing that energy is. Actually nobody has produced net energy with a fusion reactor yet, our closest bet for now is the ITER project in France. Both types of nuclear reactions (fission/fusion) produced A LOT of radiation, x-rays, gamma-rays and neutrons. The added danger of fission is the melt down, which means the chain reactions is out of control and you cannot contain it, where the fusion process just dies out if you don't supply fuel. The above project is a nice way of demonstrating the fusion process and for some (under)graduate-level research it is however in no way a energy source.</p>
<p>Josh,</p><p>Thorium is unstable and decays, while deuterium is fusionable with energy output, which are essentially opposite processes. What you could do (though I don't recommend it unless you darn well know what you're doing and also have a ton of licences and a record with radiation safety) is use the fission reactor as a &quot;breeder&quot; for thorium, to turn it into the less common, more fissile, isotope, and then essentially substitute it in for uranium. While I don't think actually building one is a good idea, if the topic interests you then you should look up thorium reactor designs - many interesting ones are basically publicly available, and I would argue that this is a cheap and relatively easy power source to replace fossil fuel power generation. </p><p>By the way, another interesting thing: fission reactors easily produce large positive power output, while fusion (what's happening here) really only has a long term positive energy out in the sun, so far. That will probably change in the next few decades, but for now thorium is an abundant and relatively (compared to uranium or even coal) safe energy source. </p>
<p>Thorium requires a particle beam to promote it up to an unstable isotope so sticking thorium in thing would do nothing, this also has the potential to be weaponised.</p>
<p>You can't use Thorium in a Fusion Reactor because Thorium is a Fission fuel. Also Thorium is usable for Fission because it converts to Uranium 233 during Neutron bombardment, but to start the reaction you need a supply of pure U233. After the reaction is underway the Thorium conversion is self-sustaining. </p>
<p>There is No such thing as a self sustaining process for one simple fact, every conversion process consumes the base matter, once the base is fully converted the process ends, regardless of energy input or output. A true self sustaining reaction is a full cyclic process</p>
<p>Thorium is a fuel used in a fission reactor. It is essentially a replacement fuel for Uranium 232. Thorium is transformed into Uranium 232 after being bombarded by neutrons traveling close to the speed of light so you need a small cyclonic particle accelerator (think tiny CERN) to make it work. <br>So no Thorium will not work. </p>
If you did turn thorium into uranium 232 youd be closer to makeing an atomic bomb if you wanted
<p>Then you would need to filter out the U-235 and purify it to 90 percent weapon grade.</p>
<p>No thorium, can't really be simplified much, no capacitor, and no power harnessing</p>
<p>can we set it up to use ( I hope I spell it right ) helium ( my spelling sucks )? </p>
<p>what there are resticshens ??? wich counchery is that ? ( sorry for spelling ) and can we use magnets to control it so make a ( by way of trikel filling and emtiying ) a sustand fusion reactor? </p>
Magnets are used in a pollywell reactor which forces tje atoms to hit each other in the middle using the velocity gained by the magnetic force
<p>No, deuterium and tritium are the only gasses that will produce fusion in a DIY fusor. Deuterium is the only one that is legal to use.</p>
<p>Can the valve be manual ones? I prefer to use manual (for simplicity) but can high voltage be dangerous that I shouldn't use a manual valve? I'm not familiar with pneumatic valves or other type of valves.Thanks in advance.</p>
<p>ty by the way </p>
<p>Thank you!</p>

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