At 03:46 PM 3/23/2010, Horace Heffner wrote:
The term in question I think is "nuclear fusion". There are many
definitions which do not mention the Coulomb barrier. However, it
appears plasma fusion is often assumed.
And the reason is obvious. Almost all known fusion is plasma,
thermonuclear fusion. The question raised by Fleischmann in 1989, by
his results, was whether or not there was any other kind. That
question could not be answered by appealing to arguments based,
essentially, on the only kind being thermonuclear fusion. It was
already false, anyway, because of MCF.
http://www.google.com/search?
hl=en&client=safari&rls=en&defl=en&q=define:nuclear+fusion&ei=tBapS-
KiN4vesgOB-pmDAw&sa=X&oi=glossary_definition&ct=title&ved=0CAgQkAE
http://tinyurl.com/ygkw3lu
Most of the definitions are a bit off. They don't match each other,
when you try to nail them down. For example, defining fusion this way:
The process in which light nuclei fuse together to make one heavier
nucleus, releasing energy as they do so.
The release of energy is a characteristic of most fusion, but if a
fusion reaction is created to absorb rather than release energy, it's
still fusion. In fact, brute force fusion is used to create new,
very-high-Z elements, and because the energy is deliberately kept low
to avoid breakup of the target nucleus, it's also called "cold
fusion," meaning at lower than normal temperatures. Still really hot.
(Basically, they go a bit below the energy required to overcome the
Coulomb barrier, depending on the (lower) reaction rate remaining at
that energy. These reactions are endothermic. Other definitions
describe the release of energy from the small loss of mass involved
in low-Z fusion. It's not part of the definition of fusion, but is a
common characteristic of most reactions that are called fusion.
Just ordinary sloppiness. Being helpful by giving examples that are
usually what a person will be interested in.
Fusion is a process which under some conditions can release energy.
The best definitions cited by Mr. Heffner involved the combination of
nuclei. This does leave ambiguous, it might seem, neutron activation,
but since the result might be the same as if direct nuclear fusion
(of unambiguous "nuclei," i.e., hydrogen on up), we'd have to call
the process a fusion process.
Fusion itself, in ordinary language means putting stuff together.
That distinguishes it from fission, which means splitting apart. With
low-Z elements, putting together generally generates heat, and with
high-Z elements, splitting apart generally generates heat.
Fission of Carbon-12 certainly doesn't generate heat, it requires
energy, but we'd still call it "fission."
Nobody is fooled by avoiding the term "fusion," and the reality is
that what is known, with high certainty, that deuterium is being
converted to helium, is, by definition, a fusion process, no matter
what hand-waving exists inside the black box.
I see that Larsen is beating the same dead horse as the skeptics (and
Krivit) at the Nature blog I just cited.
I would like to note that there is an alternative to the fantastical
notions of strong interaction D + D -> He-4 + heat "cold fusion"
reactions promoted by some of the participants in these sessions.
Now, maybe someone there is promoting a fusion theory that would be
described that way. I think, though, that nearly everyone would
agree, of late, that whatever the reaction is, it is not "strong
interaction d + d -> He-4 + heat," that simply. Quite simply, that's
not the only possible "cold fusion," and it's very obvious that
whatever is happening, it's not classical hot fusion as implied.
Absolutely, the idea is "fantastical" and we are properly very, very
skeptical about it, but such theories should not be ruled out
automatically, if mechanisms can be shown to explain the radical
deviation of experimental results from that expected from such fusion
(i.e, there is no or tritium to speak of, helium is a primary
product, but no gamma rays and no strong radiation of any known kind
are found, at levels indicated if the reaction were hot fusion or
anything quite like it, generating the known thermal energy).
Krivit, last year, objected to the SPAWAR discussion of
deuterium-tritium fusion in their triple-track paper, apparently not
realizing that, with the very low levels of neutrons involved, they
were talking about secondary reactions, not the primary reaction. It
is quite likely that any process that generates helium from deuterium
(and I'd expect this if Larsen is right as well) will sometimes
generate products that are hot enough to cause secondary reactions.
There is a recent paper by Hagelstein published in
Naturwissenschaften, setting upper limits on the energies of
products; if Hagelstein is correct, such products are very rare.
What's objectionable about Larsen's statement is similar to what's
objectionable about Krivit's, unfortunately. The uncollegial polemic
that is overenthusiastic for personal preference and overdismissive
for everything else. Some scientists are like that.
