We do not know what the reaction is.
Storms proposes that d e d (two deuterons with an
electron in between) are trapped in cracks in the
Pd, and that a slow process results in fusion
with release of energy as a series of X-rays
resonant in the crack. I and, I suspect, most
physicists, don't think much of the "slow fusion"
concept, but helium was proposed early on as the
ash, by Preparata, and Miles, who found the
correlation, considered his work a validation of Preparata's theory.
Basically, a known fusion reaction is d + d ->
He-4 plus gamma. The energy released, mostly in the gamma, is 23.8 MeV.
The first problem with this is that this is a
*very* minor branch, d + d prefers to go to
tritium plus a proton (50%) or helium-3 plus a neutron (50%).
The second problem is that, on the face, this
requires high energy to overcome the Coulomb
barrier. But some kind of catalysis, as Storms is
proposing, might overcome that, as happens with muon-catalyzed fusion.
The third problem is that the gamma is necessary
in the helium branch, to conserve momentum.
These are the classic theoretical problems of "cold fusion" conceived as d + d.
There are other possibilities. In particular,
Takahashi has done the math for a multibody
problem, finding that four deuterons, as two
deuterium molecules (with the electrons),
arranged in a tetrahedral configuration with very
low relative momentum, will collapse into a
Bose-Einstein Condensate and fuse within a
femtosecond. This would form a Beryllium-8
nucleus, which will ultimately decay into two
helium nuclei. If nothing else has happened, the
two nuclei would each have 23.8 MeV of kinetic energy.
That would be alpha radiation, which would still
be low-penetrating. But that radiation is not
seen. The Hagelstein limit (named after his 2010
paper) is about 20 KeV, for any major charged
particle radiation from PdD cold fusion.
It is possible for the excited Be-8 nucleus to
shed most of its energy by photon emissions at
low enough energies to satisfy the Hagelstein
limit, before it fissions. I'll add that,
probably, nobody knows what to expect if fusion
occurs within a Bose-Einstein Condensate.
Takahashi's study is simply of a single
possibility. The real reaction may be more
complex, there are some signs that 6D may be active instead of 4D.
(To answer an obvious question about this theory,
this could not happen with pure liquid or solid
deuterium (i.e., at very low temperatures),
because the two deuterium molecules cannot
approach closely enough, it requires some kind of
confinement to manage that. Takahashi, in his
study, assumes confinement in the palladium
lattice. Storms points out -- cogently -- that
the lattice itself is unlikely to be the site of
the reaction, and points to cracks, which could
explain a lot about cold fusion, the famous lack
of control and variability. Takahashi's idea,
though, would probably work with some cavity for
confinement other than a lattice site.)
At 04:27 PM 7/4/2012, Eric Walker wrote:
I wrote:
Assuming for the moment that the 40 MeV/4He
result is solid and can be reliably replicated,
and going with helium as a predominant
non-radiative byproduct, what does this say
about the reactions involved? Â Does it mean
that there would need to be more than helium
generation, or is there a way to work out helium
generation that produces this level of energy?
To answer my own question (using what you've already hinted at):
One way to get at this figure would be to allow
a large amount of the helium to escape. Â Then
it would seem like the residue was responsible
for the entire balance of the heat, when in fact
some of it resulted from escaped helium.
Eric
