>Luis Alvarez was the first reported observer of muon-catalyzed fusion, and >despite deuterium being present along with hydrogen in the gaseous medium, >the reaction was NOT d-d fusion.
>Asking oneself: "why not?" could be instructive. RvS ...because he was looking at ordinary Hydrogen, and only one atom in about 6800 is D, hence the chances of any given D fusing with another D rather than with H are only one in 6800. IOW it probably did happen, but would have been so rare that it wasn't noticed. Robin, A cryo bubble chamber can contain HH, DD or HD. Or really anything in between. Most often, as you are assuming - liquefied hydrogen HH which has a small amount of natural deuterium but less than water, since the H comes from methane. However, I had remembered something unusual about this one an even remember seeing the tracks - and that Alvarez was looking at HD specifically. He was. I have attempted to locate that forty year old paper online, to little avail. Alvarez's Nobel acceptance speech is online and it indicates specifically that he was looking for the most favorable reaction being in HD and for the reasons given. It turns out that, yes, initially the fist tracks had been seen HH with some natural HD present, and afterwards the HD concentration was increased and finally this was compared to DD. IOW there is NO reaction without some deuterium, and consequently any added deuterium increases the cross section, up to a point ... BUT since the muonic hydrogen atom is the first step in a two step bootstrapping process, you may need both for efficiency. There is a valid alternate first step with the muonic D atom alone, and no H at all, but he does not mention it as being useful. Perhaps the reduced near-field of a deuteron makes that required kind of muonic atom more unlikely in the short time frame, before muon decay. Furthermore, Alvarez does mention that the deuterium only reaction results in 3He + H and NO 4He. If there is a tritium branch he does not mention it. This should go down as one of the first cases of cold fusion, since it was conducted near absolute zero ! Here is the relevant quote: The resulting muonic hydrogen atom, [which is a proton bound to a muon - which displaces the electron at a fractional orbit, no less] had many of the properties of a neutron, and could diffuse freely through liquid hydrogen. When it came close to the deuteron in an HD molecule, the muon would transfer to the deuteron, because the ground state of the p-d atom is lower than that of the p-y atom, in consequence of <reduced mass> effect. The new <heavy neutron> might then recoil some distance as a result of the exchange reaction, thus explaining the gap [in the bubble chamber photos]. The final stage of capture of a proton was also energetically favorable, so a proton and deuteron could now be confined close enough together by the heavy negative muon to fuse into a 3He nucleus plus the energy given to the internally converted muon. We had a short but exhilarating experience when we thought we had solved all of the fuel problems of mankind for the rest of time. A few hasty calculations indicated that in liquid HD a single negative muon would catalyze enough fusion reactions before it decayed to supply the energy to operate an accelerator to produce more muons, with energy left over after making the liquid HD from sea water. While everyone else had been trying to solve this problem by heating hydrogen plasmas to millions of degrees, we had apparently stumbled on the solution, involving very low temperatures instead. But soon, more realistic estimates showed that we were off the mark by several orders of magnitude - a < near miss > in this kind of physics! Just before we published our results, we learned that the muon-catalysis reaction had been proposed in 1947 by Frank as an alternative explanation of what Powell et al. had assumed (correctly) to be the decay of p+ to m+. Frank suggested that it might be the reaction we had just seen in liquid hydrogen, starting with a m-.... Zel'dovitch had extended the ideas of Frank concerning this reaction, but because their papers were not known to anyone in Berkeley, we had a great deal of personal pleasure that we otherwise would have missed. I will conclude this episode by noting that we immediately increased the deuterium concentration in our liquid hydrogen and observed the expected increase in fusion reaction, and saw two examples of successive catalyses by a single muon. We also observed the catalysis of D + D -> 3H + H in pure liquid deuterium. END of quote. Three things worth noting or pursuing: 1) The HD reaction is apparently favored in a two step reaction in a liquid, but what about in a metal matrix? 2) The muon reaction does not result in substantial helium 4 - at least not in the way it was performed by Alvarez. Others have apparently seen 4He. 3He could be advantageous for the purpose of producing a marketable exotic gas in a commercial venture. 3) The comparative cross-sections for increasing the percentage of deuterium is not specified in this speech (make that number of reactions catalyzed per muon) but Alvarez had intended that the energy device "which would save the world" would fuse HD in a two-step process, as opposed to DD in a one step process. 4) Is there a virtual muon reaction? and can the probability be enhanced? An enhanced probability field for the virtual muon... has a nice ring to it.
