Fusion is a process by which two atoms/nucleii of hydrogen (a proton, possibly with neutrons attached) fuse to form an atom/nucleus of Helium (two protons, perhaps with neutrons). Since the two nucleii to be fused are positively-charged they repel each other, and to get them to fuse they have to be at a very high temperature. One hundred million degrees Kelvin or so is needed to give them enough kinetic energy to randomly collide. The sun's centre is hot enough, and it is a huge fusion reaction turning hydrogen into helium, and only avoids exploding and destroying the Solar system because of its own self-gravity, which holds it in.
Fusion releases a lot of energy, so for 70 years people have been trying to make it happen on Earth, in close confinement. So far 25 billion dollars have been spent on this (Storms, 2012) and the focus has been on huge machines that use magnetic fields to confine plasma: magnetic versions of the Sun (The so-called ITER project). Imagine the surprise then, when in 1989 Martin Fleischmann (then one of the world's experts in electro-chemistry) and Stanley Pons, claimed they had produced fusion in a little test tube! Their experiment is shown below.
They put an electrolyte containing heavy water in a test tube (heavy water is just like water H2O, but the hydrogen H is replaced by deuterium D, which has an extra neutron, so D2O). They put two electrodes in, the cathode (negative charge) made of palladium and the anode (positive) of platinum, and passed a current between them (electrolysis). The D2O separated into oxygen, which being negative headed for the anode and bubbled off, and deuterium which, being positive, packed itself into the palladium cathode, since palladium has this odd property of soaking up deuterium like a sponge. Several scientists over the past 50 years had predicted that the deuterium could fuse in palladium being in such a packed state. Apparently it did, releasing a lot of heat, see the orange-red 'star'. The announcement of that thrilled the world with the possibility of having such a FusionCell in every home. Virtually limitless cheap energy.
But revolutions are never pretty and this was the usual hysterical mess, because very soon it was noticed that if the deuterium was actually fusing, it should be emitting neutrons and gamma rays and whatever was happening wasn't doing that. A bonus for safety, but because the observations did not fit standard theory, cold fusion was classified as fringe. A few brave souls continued to investigate, and instead of cold fusion, they now call the field LENR (Low Energy Nuclear Reactions). So far there have been about 200 independent replications of the excess heating effect so something odd and potentially very useful, is certainly happening, but why?
I was persuaded to look at LENR recently by twitterer B.McIntyre who pointed out that my 2017 paper on the proton radius anomaly (link to blog entry) might have implications for LENR. His tweet exploded in my head during a tutorial the following day. A few days later I calculated the size of the effect on the train to St Andrews and it was too small, but then on the train back from St Andrews I read Ed Storms' summary (see below) and found out that LENR happens whenever there are tiny cracks in the palladium. See the gray mottled pattern on the palladium in the schematic - cracks in the palladium where the fusion happens. I have applied QI to confined cavities/horizons before (the early cosmos, emdrives, sonoluminescence..) and it changes the physics in intriguing ways..
Fleischmann, M., S. Pons, M. Hawkins, 1989. Electrochemically induced nuclear fusion of deuterium. J. Electroanal. Chem., 261, 301-308.
Storms, E., 2012. A students' guide to cold fusion. http://lenr-canr.org/acrobat/StormsEastudentsg.pdf