From: blue@nscl01.nscl.msu.edu
Subject: New Information from BYU Team
Reply-To: blue@nscl01.nscl.msu.edu
Organization: Sci.physics.fusion/Mail Gateway
Date: Mon, 4 Jan 1993 17:44:13 GMT

Recent post by S. Jones relays information provided by Profs. Jensen and
Palmer concerning the detector used in the first Jones experiment reporting
low yield neutron production from cold fusion.  I had been relying on the
following statement which I quote from the Czir-Jensen paper:

"Two useful applications for the spectrometer in the capture-spectrum
mode are: measureing the spectrum of neutrons from fusion experiments
(particularly the recent cold-fusion experiments where the expected
neutron flux is low) and measuring cosmic-ray produced neutron spectra."

This is followed immediately by the acknowledgements section which begins
with:

"We thank Professors Steven E. Jones and E. Paul Palmer for encouragement
and support in adapting the spectrometer to the present applications in
cold fusion research."

Profs. Jensen and Palmer now inform me that "The only mode used in the
experiment was the standard spectrometer mode. Nothing was added to the
signal.  The 'capture-spectrum' was not developed until after the data
used in the Nature paper was taken.  We did use it to investigate the
nature of the background."

Clearly I was mistaken as to which mode of operation had been employed
to obtain the spectrum reported in the Nature paper.  There do, however,
remain some questions as to what the reponse function of the detector
is for neutrons and for gammas.  Both Jensen and Palmer in their replies
refer to spectra obtained at 2.9 MeV and 5.2 MeV as reported in the
Czir-Jensen paper, but Jones discounts those as calibration spectra in
favor of some more recent calibrations with monoenergetic neutrons.
Not only do we seem to be getting differing answers from different
members of the team, we seem to have a situation in which information
crucial to the intepretation of the spectra was subject to revision
long after the experiment was completed.  If we are to be convinced
that the spectrum reported in Nature shows a "peak", it would be nice
to know whether the detector as operating at the time was in fact
capable of producing such a peak in response to fusion neutrons.  One
question that remains in my mind is what mechanism accounts for
the roll-off of the proton recoil response on the low side of the
peak.  Off hand I would expect the response to be close to what is
shown in the Czirr-Jensen paper.

The next question that can perhaps be laid to rest if I understand
Jensens reply has to do with the way in which the background subtraction
was made.  Jensen states: "The background HAD to be normalized [Approx
4 times more background than foreground hours], but the background
was featureless and could not generate a peak."  I take that to
mean that the background was scaled in strict ratio in accord with
the different recording times before subtraction, and no other
adjustments were made such as matching forground and background in
a region of the spectrum away from the "peak".

We are still left with the issue of the gamma response of the
detector and what fraction of the response was in fact due to
neutrons.  From other experiments which employed liquid
scintillation counters with pulse-shape discrimination to 
separate neutron and gamma response on sees cosmic-ray-induced
backgrounds showing gamma-to-neutron ratios of something like
10E3 or 10E4.  Clearly this ratio can be altered by effects
specific to the surroundings of a given experiment, but I
see a potential problem in making a determination of this
ratio with a detector that may well respond with no better
than a 100 to 1 rejection ratio for gammas.  To make that
explicite let us assume that the true ratio of gammas to
neutrons is 10E4.  Then the detector will respond to gammas
at a rate 10E2 times the neutron rate.  Under those circumstances,
or something approaching them, how do you tell what the ratio
of neutrons to gammas really is?  Jensen asserts that about 1/4
of the background is due to gammas, but how does one go about
making a determination of that number?

Dick Blue
NSCL @ MSU
Newsgroups: sci.physics.fusion