RE: in other news

["Franta, Jaroslav" <frantaj@AECL.CA>]

Title:

From: "Sandy Perle" <sandyfl@earthlink.net>

<SNIP>

Tiny bubbles create nuclear fusion -- maybe

WASHINGTON, March 4 (Reuters) - Tiny bubbles imploding in a solution of acetone may have generated nuclear fusion, Russian and U.S. scientists said on Monday, in an experiment that, if confirmed, represents a giant advance in nuclear physics.

The experiment was run in a series of beakers that would take up only a corner of any tabletop, using what amounts to souped-up nail polish remover and sound waves.

Because the collapsing bubbles produced temperatures as hot as those found in the sun, the experiment does not mean that the long-sought goal of cold fusion has been achieved, scientists warned.

But if it can be replicated, it could mean an easy way to generate nuclear energy has been found -- one that mimics what the sun does and that would be many times safer than current nuclear fission methods used by modern-day power plants and makers of atomic bombs.

<SNIP>

.........the temptation to condemn this utter nonsense is only tempered by the fact that it started with SCIENCE magazine -- the publishers of the acoustic or "bubble fusion" experiment report -- in the News article by Charles Seife (p.1808), in which he says,

That stunning claim, if true, could eventually have important consequences for nuclear proliferation and energy production.

There is nothing "stunning" about the claim, and no "giant advance in nuclear physics". Converging shockwaves are the standard technique for energy concentration. Using acoustic cavitation for this purpose is merely an interesting experiment in applied physics (numerous other techniques have been tried in the laboratory, usually involving laser ablation of small fusion fuel pellets, but also a variety of much smaller-scale, clever schemes for generating converging detonation waves with mixtures of hydrogen and oxygen, or other gaseous fuel mixtures -- some of which measured similar numbers of fusion neutrons).

But the important point is that the potential (or lack thereof) of the SL (Sono-Luminescence) fusion technique for energy application is evident from the text on page 1873 of SCIENCE VOL 295 8 MARCH 2002 ( "Evidence for Nuclear Emissions During Acoustic Cavitation," R.P.Taleyarkhan, C.D.West, J.S.Cho, R.T.Lahey Jr., R.I.Nigmatulin, R.C.Block; http://www.sciencemag.org/feature/data/hottopics/bubble/index.shtml ) :

To obtain an estimate of the D-D fusion neutron production rate, we may evaluate the fusion neutron kinetics equations and fusion cross sections (40, 41) over a range of uncertain parameters to arrive at reasonable estimates for the neutron production rate, varying from ~10^-2 to 10 neutrons per implosion [see Web supplement 2 (25)]. Direct photographic evidence of the bubble clusters suggests that there were about 1000 bubbles in each bubble cluster in our experiments. Since up to 50 implosions/s were observed during our experiments, the HYDRO code (25, 42) predictions yielded neutron production rates ranging from about 10^3 to 10^6 neutrons/s, which is qualitatively consistent with the estimates from the T production rate, and the fusion neutrons measured in our experiments.

.....I haven't seen any numbers on the total amount of (acoustic & other) energy going into the system, but I wager that its way more than that produced by several thousand to a million fusion reactions (a trillion-times more would be "useful" on a macroscopic scale).

Certainly the number of neutrons (from an external source) used to produce the nucleation sites for cavitation was larger, according to data in the report, than the number of neutrons produced as a result of the subsequent cavitation-induced fusion reactions.

Moreover, the cavitation mechanism only works at low temperatures (also verified in the series of experiments), making application in a thermodynamic energy conversion scheme completely impractical.

A colleague here took the trouble to look up some of the key fusion physics numbers :

"The cross section for a monoenergetic beam of D on stationary D target.... goes smoothly from 10^-32 at 10 keV to 5x10^-30 at 1,000 keV. It drops very quickly for anything less than 10 keV..... 10 keV, though, is 116,000,000 degrees Kelvin. The temperature they note in the paper, 10,000,000 degrees, works out to only 0.86 keV. At that temp, the DD cross section is WAY, way lower than D+n - at least 3 orders of magnitude. [.....but there ] is the chance of some quantum tunneling effect - helping fuse the acetone D's together. If that's the case, though, I think getting anywhere close to the Lawson Criteria (n*tau*T >= 5x10^21 m^-3 s keV) would be highly unlikely. "

......of course the implication of not being "anywhere close to the Lawson Criteria" means there is no possibility whatsoever of a practical energy gain with this technique (as with the old converging gas detonation wave experiments, which also benefited from the quantum tunneling effect to yield a few thousand to ~ 1E6 DD fusion reactions....).

Nor do I believe that "this new, compact apparatus will be a unique tool for studying nuclear fusion reactions in the laboratory" (according to Fred Becchetti of the University of Michigan). What is there about DD fusion that hasn't already been found out fifty years ago ?? Am I missing something here ?? Why is the science community (and SCIENCE magazine in particular) so intent confusing the media and the public ??

Jaro