At 09:25 PM 10/29/2009, Jed Rothwell wrote:
I wrote:
However, as you see in the text you quoted, I said that in my
opinion CR-39 is not "more sensitive" or "less disputable." That is
not quite the same as "less convincing."
The key point is that heat detection is more reliable. More likely
to happen. For experiments that attempt to measure both heat and
neutrons, there are hundreds of examples in which heat was detected
but neutrons were not.
Jed, that was with instantaneous electronic detectors. Integrating
detectors are another animal entirely. It was only in the last two
years or so that detection of neutrons with CR-39 was reported, and
the configuration was not at all optimized for detecting neutrons.
That's fairly easy to fix, it's just some more stuff added outside the cell.
But the "radiation" that is most copious is obviously alpha
radiation, the neutrons are almost certainly from secondary reactions
and therefore at a rate much lower than the alphas. I'm not aware of
serious efforts to detect alphas instantaneously and electronically,
i.e., perhaps with a Geiger-Mueller tube that would be built into the
cell, it must get up close and personal with the cathode. Absolutely,
it's tricky, but almost all CF experiments have been run with no
search for alphas, and the attempts to find neutrons were with
methods that we now know would largely fail. The bubble detectors are
interesting, they are integrating detectors, and they could be placed
very close to the cathode.
Heat was detected and neutrons were not because they were looking for
heat and the correlated neutron flux is quite low. But even with
neutrons, the triple tracks from SPAWAR were important because they
are quite characteristic of C-12 breakup from neutrons. And then, the
information that wasn't released before Galileo was almost over: gold
cathodes produce copious neutron radiation by comparison with silver,
which seems to produce almost none.
