I have this idea rolling in my head for quite a while, but lately I got really interested to know if it's even remotely feasible. I am complete novice to the field of nuclear engineering and cold fusion, and maybe because of my limited knowledge my idea sounds really compelling to me.

Well, here it is:

The first element is a particle accelerator, that accelerates a stream of protons to a kinetic energy sufficient to fuse them even if the other (target) particles they are supposed to collide with have very low kinetic energy (almost stationary). From the research I did, it seems that building an accelerator that can do that isn't hard at all, and it would actually be a small one (if it's a cyclotron).

The second element is a tubular container full of NEGATIVE hydrogen ions! ;) The way this can be achieved is by making the container - one of the two electrodes of a capacitor. So the inner container that holds the ions is negatively charged (so it repels them), and the outer one is the positively charged electrode. You get the idea, a container within another container with a gap between them to make a capacitor... I think this is the standard way of containing plasma. Although in this case the ion gas is held at room temperature.

Now as you might guess there must be a tiny opening in one of the ends of the tubular container so that the high speed beam of protons can enter the container and fuse with the negative hydrogen ions inside. And this is why the container has to be tubular with certain length, and it must be aligned along the path of the beam of protons so that there is maximum chance of a proton hitting and fusing with a negative ion. And as you already get the idea the fact that the target consists of a multitude of negative hydrogen ions should (I think) dramatically increase the chance of fusion! I think they would be like "guided missiles", attracting each other and colliding even if they are not originally on a tight collision course.

So colliding highly energetic protons with a dense cloud of low energy negative hydrogen ions is essential to my idea, if that can't happen than probably my idea is not worth it. Say for example the protons are so fast that the attractive forces between them and the ions simply doesn't matter.

Another concern is the density of the ion gas, it should be as dense as possible even liquid, but I don't think you can easily liquefy a mass of mutually repulsive particles.

  • So will this gas be nearly dense enough to allow all, or most of the protons to fuse with the ions?
  • Will the attractive force between the particles be enough to make a difference?
  • Is it even possible to hold such a dense cloud of ions the way I suggest?
  • If the ions are held at really low temperature in the container would that allow the density of the ion gas to increase significantly?

Also I think that the negatively charged container will not allow ions to escape through the opening, while the protons will be free to enter (if well centred to avoid colliding with the walls of the opening). The protons might need to have some more energy to compensate them being pulled back by the walls of the container after they get inside it. I don't think that would be a problem, would it?

So this is it! :)

Now since I have very little understanding in the field and my idea is probably even naive, but anyway I'd like to know exactly why it wouldn't work? :)

Thanks a lot, in advance! :)

P.S. Feel free to ask any additional questions if my explanation wasn't clear enough!

  • $\begingroup$ It could "work", but the effective cross section for successful fusion is tiny. Such a tiny fraction would fuse that you'd never come close to recovering the energy you spend in the accelerator. $\endgroup$
    – BowlOfRed
    Apr 20, 2015 at 22:04
  • $\begingroup$ I see, kind of the problem all cold fusion reactors have. But I'm interested about the idea of colliding a proton with negative ion, would that make any difference at all. Because wherever I read about fusion, everybody complains about how hard it is to fuse two protons since they repel each other? Thanks! :) $\endgroup$ Apr 21, 2015 at 5:52
  • $\begingroup$ As far as fusion goes, the ion serves no purpose other than to reduce the density of your protons. When the protons are trying to collide at a distance of $10^{-15}m$, having an ion at a distance of $10^{-10}m$ doesn't help. $\endgroup$
    – BowlOfRed
    Apr 21, 2015 at 6:28
  • $\begingroup$ Ah yes indeed. I didn't take into account the fact that electrons orbit quite far from the core, so by the time an incoming proton is about to collide (or miss) it's far past the electron cloud of the target ion so it really doesn't matter whether it's an ion or regular atom. Now that last comment of yours pretty much answers my main question so please consider pasting it as an answer so I can mark it as best answer. :) By the way are there any other designs that include beam of highly energetic protons hitting a static target of say hydrogen ice pellets or something like that? Thanks a lot!:) $\endgroup$ Apr 21, 2015 at 7:22
  • $\begingroup$ Aren't "negative hydrogen ions" electrons? $\endgroup$
    – Jiminion
    Apr 21, 2015 at 20:54

2 Answers 2


The difficulty with this sort of device is that the effective cross section of the target nuclei are so tiny. Even with a very dense target, most of your shots will miss. But you still have to consume energy to send them along. The most important thing for efficiency then is nuclei density in the target.

Making the target full of negative ions isn't going to help much. Because they are located much farther from the nucleus than is necessary for incoming nuclei to reach (electrons might be on the order of $10^{-10}$ or $10^{-11}m$ away, while nuclei need to be somewhere around $10^{-15}m$ to fuse), they can't "direct" the collision in any useful way.

Even static targets don't help much. From a per collision standpoint, the solar core isn't very efficient. It's just that it doesn't immediately lose the energy of a missed collision. (Most of) the thermal energy remains in the core to allow further collisions. In our devices, that's much more difficult to do. One source gives a successful collision rate in the sun's core as $1$ in $10^{26}$. That's a big miss rate to overcome if you lose the acceleration energy with each miss.

  • 1
    $\begingroup$ I see, so it's completely unfeasible. One last question if you don't mind :). What if the proton beam is shot into a MILE long tube full of hydrogen ice (not ions)? Would that setup produce a brief efficient fusion before the released energy turns the ice back into hot gas and explodes the whole thing? :D P.S. I know this is probably silly one since you already said the collision rate is very low even in the sun's core, but anyway... :) $\endgroup$ Apr 22, 2015 at 8:35

You seem to have invented a version of the Farnsworth Fusor, and/or its successor Polywell. Or, if you want a neutron generator you can hit something like Palladium that has absorbed a load of Deuterium with your beam, or a metal Deuteride

  • $\begingroup$ What about very cold : having crystalline hydrogen. An electric field would be applied to make a dipole and a time varying magnetic field would create a rotation. Around two lines of magnetic field the molecules of hydrogen would hit. But of course the field should be so strong to overcome the repulsion of protons that it is unfeasible. $\endgroup$
    – Cretin2
    Feb 19, 2022 at 23:46

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