Monday, January 16, 2012

"Low energy nuclear reactions" - again.

A person at NASA's Langley Research Center appears in a video touting the great benefits that are going to come with the realization of "low energy nuclear reactions", which is a phrase that is meant to be a bit more general (and a bit less tainted) than "cold fusion".  Let me take care of the preliminaries right away:
  • The experimental evidence for any of this stuff remains dodgy at best.  I've explained what most scientists would consider a threshold for reproducibility of a real phenomenon, and this just isn't there.  There's always a "secret sauce" or very particular and idiosyncratic surface treatment; there are equivocal claims about the presence or absence of fusion products and radiation; etc.  (This is the point where a true believer will show up and point out the many documents indexed here, and castigate me for not being sufficiently open-minded.  Let's just take that as read.)
  • For this to be correct, much of our knowledge of nuclear processes would have to be in severe need of correction, despite the fact that it works pretty darn well for things like nuclear reactors and the description of how the sun works.
  • Just because someone at NASA likes this, or because Brian Josephson likes it, doesn't mean it's automatically real.
  • Despite claims to the contrary, physicists would love it if something like this turned out to be true - look at the reaction of most physicists to the superluminal neutrino business.  It'd be the story of the century.  There is not some giant conspiracy of The Establishment trying to suppress this.  Again, look at the neutrino situation:  everyone agrees that such an extraordinary claim requires extraordinary evidence, presented for public scrutiny in detail.    
That being out of the way, I want to comment briefly on the supposed explanation implied by the NASA video, "Method for Enhancement of Surface Plasmon Polaritons to Initiate and Sustain LENR".  The proposed explanation, related to "Widom-Larsen theory", is related a bit to muon-catalyzed fusion.  The muon is a cousin of the electron, but 200 times heavier.  The muon can replace an electron in, e.g., a deuterium molecule, causing the two nuclei to be considerably closer to each other, and enhancing the rate of fusion.  Widom and Larsen propose that some collective coupling between nuclei and collective electronic excitations (plasmons) results in electrons with large effective masses, and that this effective mass enhancement allows "heavy" electrons to catalyze fusion reactions.  This is exceedingly unlikely to be correct, because (to paraphrase Morbo from Futurama), "Effective mass does not work that way!".  At the end of the day, while there are collective excitations of many electrons that act, at condensed matter energy scales, like they are heavy (meaning that their energy increases more slowly as a function of their (crystal) momentum than for a free electron), (1) individual electrons are what participate in things like inverse beta decay, and (2) only a small fraction of the total number of electrons in a metal participate in these "heavy" excitations. 

Again, I'd love it if this were real.  Show me reproducibility that does not require prior belief to buy, and then we can talk.


David Brown said...

Hot fusion uses enough kinetic energy to overcome the potential barriers predicted by the SU(3) X U(2) X U(1) Standard Model. It would be wonderful to have cheap and easy nuclear fusion with new physics — however, the very wonder of it is what attracts bold swindlers and messianic crackpots.

Humbly Submitted said...

"true believer" says it all. Do you think NASA knows/cares that their logo is featured at the beginning?

Anonymous said...

Replace "plasmon" with "Pd" and what do you have? Deja Vu!