voda: sonofyzika sonochemie

[Petr Krc]

hwkonfera wrote:
> > Kdysi jsem cetl o tom, ze to depolymerizuje vodu a pri one depolymeriazci
> > nekdy vznikne H + O, ktere spolu reaguji.
>
> Tech mechanizmu, teorii (zarucene vycerpavajicich) uz je nechutne mnoho ...

Zrovna mi prislo dalsi PNU (579) - fyzici uz v souvislosti se
sonoluminiscenci dokonce pry koketuji s jadernou fuzi.

Snad to nebude moc dlouhe kdyz to sem vlozim (neznam URL):

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HAS NUCLEAR FUSION BEEN OBSERVED IN A BUBBLE
TANK?  A team of scientists has claimed evidence for deuterium-
deuterium fusion in a tabletop apparatus at Oak Ridge National
Lab (Taleyarkhan et al., Science, 8 March 2002), but other
scientists (including a separate group at Oak Ridge) are raising
serious concerns about the validity of the result.   In their
experiment, Taleyarkhan et al. (a collaboration of scientists from
Oak Ridge, Rensselaer Polytechnic Institute and the Russian
Academy of Sciences) utilize sonoluminescence (SL), itself a well-
studied and highly regarded area of research (see, for example,
Updates 34, 299, 307, 327, and 355), in which powerful sound
waves sent into a liquid tank trigger the creation of single or
multiple bubbles which then collapse and release short flashes of
light.  
     Sonoluminescence, literally the conversion of sound into light,
is a remarkable process in that sound itself is not a densely packed
form of energy.  Even the sound in the most powerful car stereo
has a much lower energy density than the light in a penlight laser
beam.  In an SL experiment, however, the energy from the sound
wave gets focused into a very small region, namely a collapsing
bubble.  This highly concentrated energy heats the gas inside the
bubble to incandescent temperatures resulting in the release of
light.  The conversion of sound energy into light energy represents
an energy concentration of over a trillion.  Researchers have long
speculated whether the conditions inside the collapsing bubbles
could be made to approach the high temperatures and densities
necessary to trigger energy-producing nuclear fusion reactions
such as those that occur inside the sun.  This is a great matter of
debate, as some details of the bubble collapse and light emission
are still incompletely understood.  With this incomplete
knowledge, researchers cannot discount the possibility that the
conditions can be tweaked to generate nuclear fusion, modest as
these fusion reactions are likely to be.  However, according to
leading sonoluminescence theorist William Moss of Lawrence
Livermore National Laboratory, "We are all pretty sure that normal
SL conditions are nowhere near fusion temperatures--typical SL
temperatures don't exceed 11,000 degrees Kelvin or so, at least
from theoretical estimates"---as opposed to the millions of degrees
that nuclear fusion would typically require.  
   In the newly reported experiment, many details are similar to a
traditional SL setup: researchers aimed 19.3-kHz sound waves at a
glass flask containing deuterated acetone.  But here's the novel part
of the experiment: a pulsed neutron generator injected 14.3 MeV
neutrons into the flask, in sync with the sound waves.  The
researchers claim that the neutrons trigger the creation of
extremely small bubbles which then grow to relatively large sizes
and then collapse to generate pulses of light.  In conjunction with
the light pulses, the researchers report the detection of significant
amounts of tritium and evidence for neutrons with an energy of 2.5
MeV.  Such neutrons would be produced in the fusion of
deuterium atoms in the glass flask.  They repeated the experiment
with normal acetone (lacking deuterium) and did not detect the
tritium or neutrons.
   However, another group at Oak Ridge, consisting of D. Shapira
and M.J. Saltmarsh, attempted to reproduce the experiment, except
for the fact that they used a larger neutron/gamma-ray detector and
what they report to be a more sophisticated data acquisition system
(http://www.ornl.gov/slsite/SLan5av2.pdf).  They found a 1%
increase in the neutron/gamma ray signal when the experiment was
set up to trigger cavitation (formation of bubbles), as opposed to
when the sound wave was turned off. However, they did not find
the 10-fold increase that they expected if the reported tritium levels
occurred as a result of deuterium-deuterium fusion.  And they
found nothing when they looked for neutrons or gamma rays being
emitted in coincidence with the light pulses.  
     Outside researchers who have studied the Science paper have
expressed very significant concerns about its validity.  According
to Moss, the key measurement is the 2.5 MeV neutron peak. "If
measured neutrons are thermonuclear in origin, then there must be
a peak at 2.5MeV, and measuring and reporting that peak
constitutes a minimum requirement to support the claim of
thermonuclear origin," he says.   "Tritium production (claimed in
the paper) is not sufficient evidence, since it is difficult to
determine the source."  Moss rejects the conclusions of the paper
based on the "lack of a properly resolved neutron peak." He says,
"Extraordinary claims require unambiguous data, which they did
not provide.  This doesn't mean that thermonuclear neutrons from a
sonoluminescence source are impossible, only that they didn't
show data to support the claim."
    Seth Putterman, a leading sonoluminescence experimentalist at
UCLA, points out that the researchers claim a 1000-to-1
production of output neutrons to input neutrons that hit the
acoustically sensitive region of the resonator.  It should be
possible, he says, to turn this data into a huge signal and a clearly
detectable neutron spectrum, but this is not presented in the paper. 
He also points out that no other paper on sonoluminescence has
ever detected a single neutron as a result of the SL process.  The
authors of the Science paper have invited other researchers to
attempt to reproduce the experiments.  They say that they have
reanalyzed the Shapira and Saltmarsh data and find that these data
are actually compatible with sonofusion and provide an
independent confirmation of their controversial claim
(http://www.rpi.edu/~laheyr/SciencePaper.pdf).
     However, according to Putterman and Moss, the experiment by
Taleyarkhan et al. does nothing to resolve the question of whether
acoustic cavitation can generate nuclear fusion reactions.  "The
actual scientific experiment appears to be flawed," Putterman says. 
  "If confirmed, however," adds sonoluminescence pioneer
Lawrence Crum of the University of Washington, "it would be a
remarkable result, demonstrating that mechanical systems could
induce nuclear reactions."  However, Crum also adds, "I am very
skeptical that their results will ever be duplicated." "This is an
interesting, high-risk direction of research that should go on,"
Putterman says.  "These results may be so premature and so
flawed, however, that it may taint future attempts in the field."  

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-- 
Regards
           Petr Krc