In reply to Eric Walker's message of Wed, 9 Jan 2013 22:03:24 -0800: Hi, [snip] >I'm curious, Robin, if you know offhand of some back-of-the-envelope >calculations that would help to get a more precise handle on whether the >process would be too inefficient to sustain itself.
PS - AFAIK charged fast particles tend to lose on average about 400 eV for every atom they pass through, though that probably varies with the mass and charge of the fast particle. Also I think the fusion rate for fast D's is something like one in thousands. I think the fusion rate drops fairly rapidly with loss of energy, so a fast D has to get very lucky, and hit another D head on before it loses too much kinetic energy to other atoms. Once it's energy drops below about 5 keV, it has essentially no chance of fusing. IOW it has to hit another D head on before it passes through 15 keV / 400 eV = 38 other atoms. Even then a fusion reaction is far from guaranteed. Note also that the size of a D is minuscule compared to the size of the surrounding metal atoms, so even given a number of D's equal to the number of metal atoms, the chance of interaction with another D is tiny compared to the chance of interaction with a metal atom. Consider that the radius of a D is on the order of 100 fm (extremely generous), and a metal atom on the order of an Angstrom, the ratio of areas is about one in a million. IOW the fast D is a million time more likely to hit a metal atom than it is to hit another D. It only has to hit 38 metal atoms before it has no chance of fusing. That means the chance of even hitting another D before it loses to much energy is only about 1 in 25000. [1 - (999999/1000000)^38], and even then it still has to get lucky for a fusion reaction to happen (as opposed to simply bouncing off). Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
