Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is Muon-Catalyzed fusion possible with room temperature, gaseous Deuterium?

  1. Aug 12, 2012 #1
    I've been reading about the more or less discarded study of LEFR (Low-Energy Fusion Reactions) and I've read that the only repeatable LEFR process has been Muon-Catalyzed Fusion -- whereas the muon replaces an electron in a deuterium atom and overcomes Coloumb's barrier by attracting itself toward the proton of another deuterium atom, close enough that the strong force kicks in and the two nuclei fuse and emit the muon -- which either goes on to catalyze more reactions or (1 - 2% probability) becomes "stuck" to the emitted alpha particle.

    I've read that this has been achieved with Hydrogen isotopes (most notably deuterium) frozen in a block at around 3 or 4 Kelvin. I assume this is to bring the nuclei as close together so each muon survives longer as it spends less time attracting each pair of nuclei because it has less distance to cover.

    My question is, if I had a 2 L vacuum that I completely drained of air, then filled with 2 L of deuterium gas, could a muon stream cause significant (or measurable) amounts of fusion amongst the nuclei of the deuterium gas?

    How could I measure the energy emitted -- what physical tools would I use?

    Could I simply use muons that naturally land on Earth (10,000 per square meter per second, I believe)? Why/why not? If not, where could one obtain a steady source of muons, and how could I tell how many muons I would need per liter of 99.9999% deuterium gas?
  2. jcsd
  3. Aug 12, 2012 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    I had the same idea when I was an undergraduate.
    To see how muon catalyzed fusion is done IRL there are various purpose-build reactors.
    eg. ISIS.

    The main trouble is to reuse the muon enough before it decays to make up for the cost of producing it ... but like you, I wondered if cosmic ray muons could be used instead, since they are free.

    I worked out that even with ideal conversion, I'd need something like several square kms of collector to get a few milliWatts. The muon flux is just too low.

    The upper atmosphere is our only naturally occurring source of muons.
    Presumably we could up the flux by moving the planet closer to the Sun.

    Even though it was a dead end, I had oodles of fun reading old papers and conference procedings.
    Last edited: Aug 12, 2012
  4. Aug 12, 2012 #3


    User Avatar
    2017 Award

    Staff: Mentor

    Muons from cosmic rays are high-energetic (otherwise they would not reach the surface at all due to their short lifetime). While they can be stopped in material, deuterium is probably a bad target as it is very light. At the same time, you cannot use heavier atoms as they simply keep the muons they catch. To get the Milliwatts calculated by Simon Bridge, you probably need an insane height of your deuterium, too. 1km of water absorbs a significant part of the muons, this is equivalent to several km of frozen deuterium. Several cubic kilometers with some mW heat production inside... no way to use this. With gas and its low density, it is worse by ~3 orders of magnitude.
  5. Aug 12, 2012 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    I don't think room temperature is nearly high enough to cause significant amounts of fusion of any kind, even muon-catalyzed.
  6. Aug 12, 2012 #5


    User Avatar
    2017 Award

    Staff: Mentor

    With enough muons, you get significant fusion - fusion with muons is temperature-independent (as long as it is cold enough to have deuterium molecules).
  7. Aug 12, 2012 #6

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    @mfb: yep - I wasted a lot of time on schemes for slowing them down which usually just meant I was selecting a narrow range of speeds before I realized I could do a plausibility check really easily by just working out the collection area for a magic system. I'd also have to collect them all to the target... all kinds of problems.

    The other approach is to minimize the various processes that remove muons from the cycle like He3 poisoning.

    I suppose the simple answers to OP's questions, in order, are:
    when I last did this it was common to use neutron detectors to demonstrate fusion - and calorimetry to measure the energy output (or just rig it to do work on something).
    see above
    from a particle accelerator

    ... did I miss one?
    Tie to hear from OP - hope we are not too discouraging.
  8. Aug 12, 2012 #7
    Wow, I definitely didn't expect to find this much help here! A little disappointing, but if it was easy it would've been discovered by now.

    Note: I have a huge amount of questions and while I would love a detailed response to each question, I understand that this is unrealistic and I would be grateful of a response to any individual question.

    So, basically, the deuterium must be frozen to a very low degree Kelvin because it must be thicker to catch the deuterium? It has nothing to do with bringing the nuclei closer together? Is there any way to test or calculate which element or isotope is the perfect mass for catching deuterium? If water catches deuterium, H20 atoms wouldn't fuse simply because they have more than one electron and the muon can only replace one?

    I looked into calorimeters but it seems like most of these devices are based on burning an object in a vessel surrounded by water, and comparing the water's pre- and post-reaction temperatures to determine the energy change. How would this work with a block of frozen deuterium?

    When you talk about the various processes that remove muons from the cycle, I thought the only such thing was the alpha particle sticking possibility of 1 or 2%. What is He3 poisoning and what other problems exist? Could the alpha sticking possibility be overcome with the implementation of charged electromagnets (e.g. the deuterium is in a cylindrical tube, a muon source enters at the leftmost end, and the negative electromagnet is affixed to the rightmost end of the tube. Muons would be literally dragged from deuterium to deuterium)?

    I've read about amateurs setting up fusion reactors in their backyards with deuterium extracted heavy water or with deuterium gas. Somehow they could stimulate dd fusion with copious amounts of energy and, from what I've read, it seems they simply expose an electrode into the chamber filled with deuterium gas and run the electricity down the electrode into the gas. How is this done? Could it be done with other gases? How does one calculate how much electricity is necessary per liter of fuel? And, more importantly than the other questions, could electricity supplement part of energy necessary for the fusion reaction in a gas while muons (possibly from the sun in very small quantities of the gas) overcome Coloumb's barrier? It seems that excited deuterium gas would be much easier to fuse with the help of a muon.
  9. Aug 12, 2012 #8


    User Avatar
    2017 Award

    Staff: Mentor

    Solid deuterium decreases the time between fusion processes, and therefore increases the rate of fusion reactions per muon. It works with deuterium gas, too, but the fusion rate is lower and the required volume is larger. It is not useful to freeze it - if you want to use that as heat source, it should be hotter than the environment. Pressure is better.
    Not the fusing nuclei. It just reduces the flight distance of the muons.
    Deuterium or muons? In case of muons: Probably all heavy elements. Heavier is better. However, muons caught by a heavy nucleus will not go to any deuterium to induce fusion.
    Again, I think you mean muons. In D2O molecules (not atoms), the hydrogen nuclei are separated with oxygen in between (not in the middle, but enough to ruin the concept). The muon would replace one of the inner electrons of the oxygen.
    You do not need water to measure the temperature, the same system works without water, too.
    And the muon decay.
    Muons can stay at the new helium atom they "produced", but they can also be caught by another helium atom from a different fusion process, if you do not remove them quick enough.
    I do not see how. This sticking occurs on a length scale of ~10^(-13)m, no reasonable static field can influence the muon/helium system in any relevant way.
    There is no such thing as a "charged electromagnet" or I do not know what you mean.
    What? Do you have any reliable source for this? Maybe you are confusing this with some sort of electrolysis?
    I have no idea what you mean here.
  10. Aug 12, 2012 #9


    User Avatar
    Staff Emeritus
    Science Advisor

    Yes amateur fusion can be done at home. Look up the Fusor. Id explain more but mobile devices and typing don't mix well.

    Could someone explain how a muon causes nuclei to get so close together?
  11. Aug 12, 2012 #10
    First off, sorry, I made a few mistakes late last night.

    EDIT: I can only find stories of amateur fusion and/or websites of professionals with little to no information published. Is the Fusor some sort of commonly known device? Where could I find its plans or learn how one works or how to build one?

    Yes, I meant muons. Why are heavy elements better candidates for fusion (between two heavy atoms)? I thought they would be harder to bring together and the muons themselves would have less of an effect with more electrons?

    This one was kind of funny. I meant H20 molecules and muons. So basically, muons don't have a significant effect on water because a muon would be trapped in an Oxygen orbital, and wouldn't be large enough or attractive enough to bring the Oxygen in one H20 molecule close enough to another Oxygen in a separate H20 molecule in order to overcome Coloumb's barrier and cause the two to fuse?

    So basically, if I wanted to use a calorimeter to measure energy released by fusion of deuterium gas, I would have a chamber of highly pressurized deuterium gas being acted upon by a source of muons -- and I would have what to measure the temperature?

    I don't think I could easily calculate the temperature with traditional formulas, even if I recorded changes in pressure, because I would be unsure as to how much of the deuterium gas had truly been fused.

    I meant an electromagnet with a live current. So, there hasn't been much research into preventing alpha particle sticking? I haven't been able to find any documents or experimental suggestions regarding how to solve this sticking problem. Is there any at all?


    Those are the two tabs I still have open from last night. I know there's another electronic deuterium fusor out there, made by an adult, but I'm afraid I've closed the tab. Perhaps I've saved a link to it somewhere.

    Would a device like this help muons to fuse pressured deuterium gas?

    Could one simply construct a glass vacuum chamber, suck out all the air, pump in as much deuterium gas as possible, run electricity through the electrode and record increases in temperature (using the electricity to supplement or completely replace muons resulting from cosmic rays)?
    Last edited: Aug 12, 2012
  12. Aug 12, 2012 #11


    User Avatar
    2017 Award

    Staff: Mentor

    Ah, that thing. Well, a power plant based on this would be more interesting.

    Consider a single hydrogen atom with an electron around it: The size of the orbital corresponds to a solution of the Schroedinger equation, and it depends on the mass of the electron. The binding energy is proportional to the mass. Therefore, if you replace the electron with a muon, you increase the binding energy by a factor of ~200, which corresponds to a reduced radius by a factor of ~200.
    In DD molecules, you get the same thing. The binding length is determined by the orbitals of the electrons/muons. It would be better to replace both electrons, but replacing one is sufficient.

    They are not (they are worse). But they are better in catching muons as their charge is larger.

    Yes. Oxygen has a charge of 8, this increases the repulsion between two nuclei by a factor of 64 (and a single muon cannot change this enough).

    In theory, this can work. There are better ways to detect fusion, however, especially the neutron flux.

    The last part is the result of your measurement ;).

    I think there was, but electric fields do not help at all. In fact, I do not see any practical way to solve it, and as we do not have muon fusion power plants yet, I think I am not alone in that respect...
    Maybe you can removed the muons with intense lasers or something like that, but I doubt that the efficiency would be relevant.


    Not really.
    Last edited: Aug 12, 2012
  13. Aug 12, 2012 #12
    How could that fusor possibly work? How does throwing a bunch of electricity at deuterium gas suddenly cause it to fuse?

    Also, why would a powerplant be more interesting?

    How could an amateur detect neutron flux with a self-built fusor, or something like it?

    Why not? I meant, could a chamber filled with pressurized deuterium gas record (minuscule) heat increases as a result of muon-catalyzed fusion due to muons propagating from cosmic ray interactions? If not, could using a system of electricity, similar to those in the linked amateur fusors (running electricity into a chamber filled with pressurized deuterium gas), assist muons dropping to Earth in fusing more deuterium?

    Why not? I know it wouldn't be efficient, but couldn't one determine the ideal amount of electricity for a specific volume of deuterium?

    Could one use any pure gas (e.g. 99.9999% helium, or deuterium) in an amateur fusor like the one in my links?
    Last edited: Aug 12, 2012
  14. Aug 13, 2012 #13

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    There's http://en.wikipedia.org/wiki/Polywell]Bussard's "Polywell" fusor [Broken]. It has attracted some academic interest eg. Santarius J. F.
    Performance of Polywell inertial-electrostatic confinement for applications;
    (Plasma Science, 1995. IEEE Conference Record - Abstracts., 1995 IEEE International Conference on)
    ... trouble finding anything in more stringently peer-reviewed publications. There's a bunch of Bussards papers from the 70's though.

    The fusors featured in the links are along the lines of this one
    My first pass through it I cannot tell how much is pseudoscience - there is a lot of waffle in it. The idea seems to be to use electrostatic containment to give a particle beam many passes through the target. Particles are mostly scattered off the target nuclei ... conceptually each pass has a small chance of fusing so lots of passes is good right?

    The thing with fusion is not in getting the reaction to happen at all so much as getting a sustainable reaction. This is the problem with the muons remember?

    You also need to be aware that here is a LOT of pseudoscience and just plain junk science in the amateur fusion crowd. Be very careful. If the devices worked the way the proponents often claim then we'd be using them commercially by now and the academic literature would be full of models describing them.
    Last edited by a moderator: May 6, 2017
  15. Aug 13, 2012 #14


    User Avatar
    2017 Award

    Staff: Mentor

    The key point is that the potential difference accelerates deuterium towards the central area, where it can hit other deuterium nuclei with high velocity.

    It would give access to a (relatively) clean and nearly unlimited source of electricity.

    No idea, but I would expect there are methods to do this. Detecting heat is tricky, as you always add some energy to the system, and you have to take this into account as well as heat losses to the environment and other effects.

    As already calculated, the effect is too tiny to be measurable even with high-tech equipment.

    No. These are two completely different ways to get fusion - one requires deuterium molecules and does not work with high-energetic collisions, one requires high-energetic collisions and does not use deuterium molecules.

    There is no such thing as "amount of electricity" you "add" to a volume. Look how the fusor concept works.

    Helium is useless there, you cannot fuse it. Deuterium is useful for a fusor - it is the fuel which gets fused.
  16. Aug 13, 2012 #15
    Ohh, I understand, I was very much confused before.

    So why isn't break even being achieved with these amateur, or electrostatic fusors?

    Okay, just to make sure, muon-catalyzed fusion isn't compatible with high-energetic deuterium gas because muon-catalyzed fusion requires muons to be relatively close to the nucleus and thus at a lower energy state (also because excited electrons in other deuterium atoms that the muon is supposed to fuse with the nucleus of its own deuterium atom are farther from the target nucleus and thus make the process of fusion via muon generally more difficult)?

    Clearly I have a misconception of fusion. I thought anything lighter than Iron can fuse at extreme temperatures while anything heavier than Iron would fission. Thus I believed that any alternative fusion processes (besides muon type fusion, dependent on the number of electrons) would function for anything lighter than Iron. Why wouldn't the Helium be affected by the potential difference and accelerate towards the area of low electric potential fast enough to fuse with other Helium atoms which are doing the same?
  17. Aug 13, 2012 #16
    That's exactly the type of thing I'm looking for. I don't understand how the electrons introduced to the polywell (pure electrons, right? Wouldn't it take a lot of energy to extract and contain the electrons from a group of atoms?) are retained in the middle to create a negative potential well. I looked up magnetic containment, but I can't really understand how it applies to the polywell or what devices of magnetic containment are used in the polywell to keep the electrons in the middle. It seems like the electrons would fly in (attracted by positive electromagnets), then would be doubly forced out -- first by the attraction of the positive electromagnet that brought it in, and second because the area it had just entered (the well) would be full of other similar electrons, meaning it would seek an area of low electric potential which would be outside of the well.

    Also, when it says "Ions are injected into the device," does that mean that positive ions (potentially those from which the initial electrons were harvested) are put inside the MaGrid? This seems like it would be hard to do, as any injection method (tubes, beams) would be thwarted by the still active positive electromagnets. I understand that once the ions did successfully enter the MaGrid and were attracted to the well and were additionally pushed towards the well by the positive electromagnets, they would be very strongly held together and fusion would be possible.

    So, my questions are:
    1. How do the electrons stay in the middle of the MaGrid to create a negative potential well?
    2. From where are the electrons harvested?
    3. What is the charge of the ions and from where are the ions harvested?
    4. How are the ions injected into the device?
    5. Could the electromagnets that form the MaGrid be temporarily killed so that the positive ions could be introduced? Would this disrupt the negative potential well of electrons?
    6. How does one determine the electron to ion ratio or how much electricity should be run through the electromagnets?
    7. Wouldn't the electrons that form the negative potential well get in the way of the fusion of the ions?
    8. Why doesn't this achieve break-even (I assume if it did we would be using it everyday)?
    9. Would detecting neutron flux be the most effective method of measuring fusion effectiveness in this device?
    10. How is Bremsstrahlung loss calculated? I know it's been calculated before for this device, but there is controversy and I would like to learn how to do it myself even if it takes longer than actually understanding the polywell.
    11. How does one tell how large the electromagnets must be or what their charge must be in order to project no field in the very center of the MaGrid?
    12. How does the mass of the electrons act as a "big point charge"?

    So basically it's a beam of deuterium atoms shooting at other deuterium atoms, achieved by electrostatic containment. The problem with this is the same as the problem with muons in that fusion can sometimes be achieved but not to any great or even measurable degree.

    You also need to be aware that here is a LOT of pseudoscience and just plain junk science in the amateur fusion crowd. Be very careful. If the devices worked the way the proponents often claim then we'd be using them commercially by now and the academic literature would be full of models describing them.[/QUOTE]
    Last edited by a moderator: May 6, 2017
  18. Aug 13, 2012 #17


    User Avatar
    Staff Emeritus
    Science Advisor

    A combination of magnetic fields and positively charging the magrid so that any that escape confinement are simply attracted back in. It does take energy to remove the electrons and hold them in place, so the primary purpose of the matrix is to keep the electrons confined to the center of the device and not hitting the grid or the vacuum vessel.

    Electromagnets do not attract or repulse charges in the way you think. Instead the charges will move away from a magnet if there is a gradient in the magnetic field. The electrons are repulsed by the other electrons, but the magnetic field keeps them in place for the most part.

    The ions are attracted to the negative well, but this mostly just makes them oscillate back and forth through the center until a collision with another ion finally causes fusion. The more electrons in the well the denser you can make the ions, but the harder everything is to contain.
  19. Aug 13, 2012 #18


    User Avatar
    2017 Award

    Staff: Mentor

    Engineering issues. It is hard to get significant amounts of fusion.


    Take a wire, heat it (with a current flow inside), and some electrons will leave the wire. This is used in CRT monitors, for example. It requires some energy, but this is negligible compared to the energy scale of fusion processes.

    It is easier to use some metals to get electrons and have a separate deuterium ion source.

    While the binding energy per nucleon has a maximum at iron, this is not true. There are many possible fusion processes, and usually they release energy, but this does not mean you can simply fuse anything with anything. Fusion two He-4-nuclei would yield Be-8, which (nearly) instantly decays intwo two He-4 nuclei again. It is possible to fuse 3 He-4 nuclei to C-12, but this process is extremely rare.

    1. Mainly magnetic fields
    2. See above
    3. I would expect to have mainly D+, produced with electric arcs.
    4. You can control charged objects with magnetic fields. See CRT monitors how beams of charged objects can be created.
    5. I do not think the question makes sense.
    6. Testing.
    7. How should they be "in the way"?
    8. Engineering issue
    9. If fusion processes are rare, probably
    10. With formulas for Bremsstrahlung probabilities and probably a simulation of the setup to get electron/ion density and movement
    11. Simulation of the setup or experimental tests
    12. Many electrons in a small region => large charge in a small region
  20. Aug 13, 2012 #19
    So only opposite poles would experience the effect of a magnetic field radiant (as they approach the opposite pole that is the electromagnet)? I'm having a little bit of trouble understanding this from what I've found so far.

    I found how electron guns work, but not how magnetic fields control these charged objects. All I read just said that electron guns light up the phosphorus on a screen.

    Okay, assuming these minor problems will be relatively easy to work out and understand, what would be my first steps toward creating a small model (WB-2 style) Polywell? How can I learn to make the electromagnet coils myself, how do I run voltage through them, and what should the MaGrid be constructed from?
  21. Aug 13, 2012 #20


    User Avatar
    Staff Emeritus
    Science Advisor

    A charged particle experiences a force that is perpindicular to it's direction of motion and the magnetic field. This means that a moving charge will spiral around a magnetic field line in a static magnetic field that has no gradient. See the Lorentz force law.

    This is beyond the scope of this forum to teach. A fusion device is capable of killing or injuring you and others and without knowing the basics of electrical safety and the hazards of radiation I highly recommend not attempting this project. And I believe forum rules prohibit discussions of building hazardous devices. I mean seriously, if you don't even know how to run current through an electromagnet you have zero chance of doing this. You need to learn about electromagnetism, electrical circuits, radiation safety, along with a few other things that I can't remember at the moment.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook