At 01:36 AM 6/2/2011, you wrote:
Not being very competent or informed, I searched Google to find expert
critiques of Widom-Larsen theory:
Well, no theories should be rejected completely, because it's always
possible that a theory is merely incomplete. I've never seen an
explanation of W-L that actually looked at what it would predict --
all of the predictions, not just cherry-picked ones -- and compared
this with experiment.
The problems with WL theory are this.
1. It postulates a series of unknowns, physical phenomena assumed to
be possible or to exist, without experimental evidence.
2. In at least one case, it's been claimed by Larsen that
experimental evidence exists, but couldn't be published because it
was proprietary. Indeed. This piece of evidence would, itself, be of
enormous import. It's about the alleged shielding of gamma radiation
by the heavy electrons that are postulated.
3. The proposed formation of ULM neutrons would produce many
transmutations, at high levels, that are not observed. Transmutation
is observed in LENR experiments, but generally at very low levels.
The only transmutation in classic PdD cold fusion that occurs at high
levels (in relation to the heat) is deuterium -> helium. (To be fair,
the "fuel" might not be deuterium, and the heat/helium ratio that
supports the fuel being deuterium might be explained by analytical
bias; still, it's difficult to imagine a different reaction sequence
that explains the heat/helium evidence.
4. There are reaction rate problems. Widom-Larsen theory proposes
sequential reactions to explain, for example, the appearance of
helium. Because the intermediate products proposed are not observed,
it's necessary to assume, first, a very low reaction rate for the
primary reaction (equal to the rate of the final product), then a
very high reaction rate for the next step or steps in the sequence.
How can that very high reaction rate be explained, where the
intermetiate products would still be present at a very low incidence?
I.e., neutrons at level X, very low, are generated and 100% react
with local nuclei to form intermediate product Y. If the neutrons
being generated are limited in number, and the original, unaffected
nuclei are still, by far, the most abundant, then very few of the new
Y nuclei would be affected by them. Almost all Y would remain, only a
tiny amount would then react further.
5. Gamma radiation would be emitted by nuclei that have absorbed the
ULM neutrons (which are basically very slow neutrons, that's all,
i.e., slow neutrons with an extremely high capture cross section, the
idea is that they WILL be captured locally}. These gammas are not observed.
6. To explain the absence of gamma, it's proposed that the same heavy
electrons that allegedly form these neutrons also absorb the gammas.
However, for this to work, the shielding has to be almost complete.
What about edge effects, what happens at the edges of the phenomenon?
7. W-L theory seems to have caught on with some simply because,
allegedly, "it's not fusion." But that's a purely semantic
distinction. We know that helium is being produced, and the W-L
mechanism starts with deuterium and electrons that are catalytic in
effect. And if it ends with fusion, it's a fusion reaction sequence,
and will have the known fusion heat/product ratio for
deuterium/helium. In order for the ratio to be different, there must
be different products, in quantities that are comparable. Those are
not observed.
8. It seems that this idea that it's not fusion is based on
considering fusion to be only d-d fusion, or the like. That's
artificial. If we start with low-Z nuclei and end up with higher-Z
nuclei, we have fusion, in a more sensible understanding. From this
point of view, neutron capture is a form of fusion, of "neutronium"
with itself, or a higher-Z nucleus.
9. Apparently the formation of these neutrons, while theoretically
possible, would take very high energy. Where would that come from?
Because slow neutrons are highly reactive, they are easy to detect.
Why have such neutrons not been detected, by the formation of the
expected reaction products that are seen with slow neutrons in
neutron activation analysis?
"Cold fusion" came to be the term for all low-energy nuclear
reactions, in fact. It's possible that some will be found that don't
involve fusion, but there is pretty much only one other possibility:
fission. And I don't think we want to go there.
By all means, research into cold fusion theory is warranted and
needed. W-L seems not very likely to me, but, we must remember, the
whole thing seemed pretty unlikely.
