From: Dan Clemmensen (dgc@cox.rr.com)
Date: Mon Mar 04 2002 - 19:57:50 MST
hal@finney.org wrote:
>
> Even if confirmed, this result would probably not lend itself to
> the water-fueled cars and other fantasies that the Utah cold fusion
> experiments suggested. It would be mostly useful as an inexpensive
> testbed for nuclear fusion research. But it would certainly be
> amazing if an exotic phenomonen like fusion could be produced using
> sonoluminescence, which is simple enough to be the subject of amateur
> experiments (http://www.ucl.ac.uk/~ucapwas/sl/sono.html).
>
Amazing, yes, but not implausible. With cold fusion, there was no
plausible mechanism: That is, there was never a reasonable explanation
as to how a catalyst could cause hydrogen atoms to collide fast enough
to overcome electrostatic repulsion of the nuclei.
By contrast, SBSL (single-bubble sonoluminescence) is not completely
understood, but the most reasonable physical explanation is that the
bubble glows due to simple blackbody radiation pursuant to compression.
You actually need to work hard to come up with an alternative
explanation. If the glow is black-body, then the bubble is heating to
at least 43,000 Kelvin. This is very close to hot enough for
classical thermonuclear fusion.
In SBSL, you start with a de-gassed liquid (normally water) and then
dissolve a small amount of gas (typically air) into it. Place the
liquid into a chamber and hit it with pressure waves. The easy way to
do this is with piezoelectric transducers. A standard setup uses a
spherical container and two piezos. You tune the setup to resonate,
and introduce a tiny bubble of the same gas. The bubble migrates to
the resonant pressure node at the center of the chamber and begins
pulsing at the resonant frequency. For 60mm diameter chamber the
frequency is about 20Khz. When you increase power to the transducers,
the bubble collapses and comes back into existence on each cycle: At
the point of collapse, it emits a blue glow. The simplest explanation
for the glow is simple adiabatic heating due to pressure as the pressure
wave hits the bubble. If this explanation is valid, its a blackbody
glow of at least 43,000K: It may be higher, but the water is opaque to
higher frequencies and its really hard to tell. The bubble collapse is
so sudden that the light pulse is <<1ns, so it takes exotic instruments
to examine the time and frequency spectra of the pulse.
Straight-up blackbody heating of a symmetrically-collapsing bubble is
the most parsimonious explanation, but the phenomenon is so strange that
lots of other explanations have been tried. None had succeeded very well
as of four years ago when I studied this stuff a little.
IF (BIG IF) fusion is demonstrated, then there may be ways to scale this
phenomenon. By decreasing the chamber size, you can increase the pulse
rate. reduce to a 1mm diameter chamber and increase the pulse rate to
about 1Mhz, and maybe you get enough fusion to be useful. The trick is
to design a set of thousands of tiny chambers will the correct
resonant characteristics. Note the at a 1MHz pulse rate and the pulse
duty cycle is still < .001..
This archive was generated by hypermail 2.1.5 : Sat Nov 02 2002 - 09:12:45 MST