A friend of mine recently bent my ear for an evening over cold fusion. It struck me as pseudo-science, but not wanted to be prejudiced, I spent some time with a web browser looking into it.
Though I still have a hard time believing some of these claims, I have to admit that this technology shows promise.
The Coulomb barrier that must be overcome to fuse two protons is about 5 MeV – not something you’d expect at room temperature, but well within the range of a standard particle accelerator. The problem is the minute cross section of the nucleus – protons with enough energy to fuse are far more likely to be scattered away from each other unless they are precisely aligned in a head-on collision.
That’s where the cold fusion claims start to get interesting. All of the cold fusion reports that I read involved palladium as a catalyst. Now palladium has the unusual property that it can absorb significant quantities of hydrogen. There doesn’t seem to be a consensus on exactly how this works, but one explanation is that the hydrogen nuclei can move fairly freely within the palladium crystal mesh. Now if I wanted to line something up at atomic dimensions, a crystal would be the obvious choice, and if I wanted to line something up while its moving, then I would want a crystal that allowed my particle mobility. So palladium seems like an obvious choice to line up moving protons to precisely collide them.
The approach I’m thinking of right now is to use a particle accelerator to achieve the energies needed for fusion, since I still don’t see it happening with only thermal or low voltage electrical energy, but to fire the accelerated protons into a palladium crystal in order to achieve the alignment necessary for fusion.
We could model this theoretically using Schroedinger’s equation, but actually solving this equation seems very daunting. A more promising approach would be to run some experiments to examine how proton beams interact with palladium crystals. In the limit as the energy approaches zero, the crystal should just absorb the beam, since it absorbs elemental hydrogen, so we can expect some kind of interesting behavior. I’d particularly hope to find some special angles and probably special energies at which a proton beam, fired into a palladium crystal, can travel for significant distances within the crystal with only mild dissipation. Common sense now tells us that such a beam will eventually become aligned with the crystal, and if two such beams are fired into a large enough crystal from opposite ends, they will hopefully be aligned by the time they meet and the middle and we’ll stand a good chance of getting a nuclear fusion reaction.
Carrying this one step further, we’d like to minimize the thermal vibrations of that crystal in order to maximize its alignment, so I’d like to conduct these experiments not only at room temperature, but also at low temperatures, say liquid nitrogen and liquid helium temperatures. It would be ironic indeed if the primary problem with cold fusion to date is that it isn’t cold enough.