On Oct 27, 2009, at 3:19 AM, Michel Jullian wrote:
What they demonstrate, IMHO, is that the SPAWAR pits occur:
1/ when the deposit is dendritic, not when it is spongy, and
Which, in view of large etching effects from minor scratching, places
into serious question any results in the presences of dendritic
growth adjacent to the CR39.
2/ when the CR-39 chip is in direct contact with the cathode wire, not
when a 6 micron mylar is interposed
Both the large and small SPAWAR pits (possibly due to alphas and
protons) *do* (in other SPAWAR experiments) occur when 6 micron mylar
is present, just not in the same quantities or proportions, and
obviously not using the same protocol.
Result 2/ does NOT prove conclusively IMHO that any alpha particles
produced are less energetic than the ~1MeV needed to go through 6µm of
mylar as they suggest,
Their conclusion is: "Our results do not provide a positive
identification of the origin of SPAWAR pits. However, they do show
that chemical origin is a distinct possibility and therefore that
nuclear origin is not a certainty. The accelerated etching rate
observed for CR-39 that has soaked in TGP electrolyte for several
weeks proves that there is a chemical interaction. The observation
that SPAWAR pits are visible before etching shows that they are
unlike the tracks made by ionizing particles. The observation that
SPAWAR pits are stopped by a 6 micron Mylar film is consistent with a
chemical origin but only proves that they cannot be due to nuclear
particles which would penetrate such a barrier (e.g. alpha particles
of energy >1 MeV). The rest of our observations, such as the
invariance of the result when the electrolyte is changed from heavy
water to light water, are less conclusive but are still consistent
with chemical origin of SPAWAR pits."
"It has been suggested that SPAWAR pits are a mixture of chemical and
nuclear pits. This is a difficult hypothesis to evaluate. Frankly,
the idea of trying to identify pits which "look nuclear" is not very
appealing from an objectivity standpoint."
This conclusion is clearly valid for the *Earthtech experiment*, and
possibly for the Galileo protocol, but obviously not valid for the
range of all such experiments, since there is a wide range of results
depending on conditions. It would have of course been better if the
conclusions were more highly qualified, especially in view of later
results, but it doesn't take a lot of interpretation to understand them.
What the Earthech results do show beyond any reasonable doubt is is
the Galileo protocol is highly flawed and the results are far from
convincing. They also show it is nonsensical to expose the CR-39 to
the electrolyte, because the results are then not reliable.
As I'm sure you know, determination of the nature of particles from
CR-39 tracks is a difficult, and one that can depend on computer
simulations of track shapes over different etching periods. It
depends on a reliable etching rate, and knowing etching rates as a
function of temperature.
another possibility that occurs to me is that
the material in direct contact with the cathode wire matters, i.e.
that CR-39 induces a nuclear effect and mylar doesn't. Has this
possibility been considered?
Michel
Could be examined by placing a 6 mil mylar cover over the mylar chip
for a control. It would indeed be strange if a difference were
found, because they are both composed of only H, C, and O. Mylar is
PET (C10H8O4). See
http://tinyurl.com/yp6ld5
for chemical structure of CR-39. The primary effect would be one due
to density I would think, and thus possibly related to neutron
moderation or thermalization, knock on proton creation, carbon
reactions, etc.
2009/10/27 Michel Jullian <michelj...@gmail.com>
...
http://www.earthtech.org/CR39/index.html
I don't know if he has read them but I pointed Abd to the Earthtech
results too, very early on. Not because they disprove the nuclear
origin of the SPAWAR pits, which they don't
...
I don't think anyone said the Earthtech results disprove the nuclear
origin of the SPAWAR pits. This is a strawman argument.
What they did prove is that placing CR39 in the electrolyte
dramatically changes the etching rate, and thus presumably the track
making characteristics, with depth, and the effect by depth varies
with time of exposure. They also demonstrated chemically produced
tracks.
Here are some prior comments that relate to some of the above
discussion:
On Jun 18, 2009, at 6:00 PM, Horace Heffner wrote:
It may be possible to gain some discriminatory information of
particle type by depositing very thin layers of materials on a
CR-39 detector, and then removing them prior to NaOH etching.
This would tell something about the ballistic collision cross
section of the particles with the thin layer chosen, and, if recoil
interaction with the layer is occurring, should provide many more
elliptical tracks than without the thin layer.
Thin but covering layers of vacuum deposited metals might work, as
they can readily be removed by acid bath. To protect from an
electrolyte, it might be necessary to coat some surfaces with thin
protective coatings which can be removed by appropriate choice of
solvent that does not also affect CR-39. It may be possible to use
such a protective coating material, even in lieu of a vacuum
deposited metal, as a supporting matrix for some kinds of
materials, like barium, boron, or possibly materials that can be
neutron activated and then removed for separate long term counting
by other means.
It may be feasible to make an integrating neutron counter by
adhering a boron containing layer covered piece of CR-39 to the
back of the CR-39 detector. This provides a layer of boron
sandwiched between two pieces of CR-39. This then uses the main
CR-39 detector as a moderator, the boron layer as an alpha
generator, and the two surfaces adjacent to the boron layer for
etching to look for alphas from the boron layer.
It may be of use to use BC-720 plastic from Bicron Inc. as a
scintillation detector. It could be appended to the CR-39, or used
instead of the CR-39, as a base for the cathode layer, especially
using an initial silver layer, and simultaneously as part of the
electrolysis cell wall, in order to readily position the
photomultiplier tube near it.
There are of course endless combinations of means for
discriminating particle types using these kinds of surface
treatments and sandwiching techniques. Some of these approaches can
be used with film detectors as well.
Something that may also be of utility is re-curing CR-39 prior to
use, especially if it is old, and especially if tracks are
uncovered upon successive etchings and there is concern they may be
due to neutrons. Cosmic ray secondaries cause tracks originating
within the CR-39. In any case it is desirable to have as clean as
possible an etching, and to be able to make use of old CR-39. The
following manufacturer's bulletin contains a cure cycle for CR-39.
http://tinyurl.com/yp6ld5
http://corporateportal.ppg.com/NR/rdonlyres/
3161A365-5C86-484F-97B6-74059920D2B6/0/CR39.pdf
It is also noteworthy that the electrolytic cell operating
temperature, thermal gradients in the CR-39 during cell operation,
and the duration of the run, can have an effect on the nature of
the CR-39 tracks detected by etching. If the cell operates at
temperatures sufficient to fully or partially cure tracks, then the
size and length of tracks which are detected will be affected by
highly localized temperature differences and duration of track
existence. Locally hot zones, say near hot cathode wire surfaces,
may actually reduce track diameters detected for particles in close
vicinity, by curing them to some degree before etching. In a hot
electrolyte, pe-existing tracks, say from cosmic rays, may be cured
out of existence at the surface, but still exist at depth.
These CR-39 curing issues may or may not affect a given experiment,
but certainly may be worthy of consideration when designing or
evaluating experimental controls or models of track etching.
It is notable that CR-39 curing, which depends on temperature and
duration, not only can affect track geometry according to the CR-39
history and experimental conditions, but also during the etching
process itself. The curing process should be capable of annealing
tracks altogether, or reducing their diameters or even etching
rates. One manufacturer's recommended curing process ranges in
temperature between 44 Deg. C to 90 Deg. C, and for a total
duration of 19 hours (see http://tinyurl.com/yp6ld5). These
process numbers are all right in the range of the approximately 70
deg. C etching temperature process used in the SPAWAR experiments.
Precision temperature control and etching time control are thus
critical to the etching process, and the effects of the CR-39
curing rate likely should be investigated and may be a parameter to
be considered in any comprehensive model of track etching.
A sample problem, due to a short etching once well above 70 deg. C
and then later less than 70 deg. C is that cosmic ray caused tracks
might appear in the second etch that don't in the first etch. That
is because the surface layer tracks can anneal out due to the high
temperature.
The price of CR-39 is quite bothersome for amateurs like me though.
It would be good to find a cheaper alternative! It could be that
curing your own CR-39 would be of use, and that would provide some
possibly very handy control of layer thickness. It would be pretty
neat to be able to use ultra thin layers, possibly separated by
discriminating materials, whether the layers are created by build-
up and curing, or by stacking and pressing. It is also notable
that thin metal coated plastics can be and are produced
commercially in roll form in large quantities cheaply. The problem
then is to find and prove out an alternative to CR-39. This kind
of effort is unfortunately probably not economically justified,
unless maybe it could result in improved dosimeters.
CR-39 is made by curing a monomer, i.e. forming cross-linked
polymerization. Track formation is due to breaking of the polymer
bonds by ionization. It is to me self evident the same thermal
process of polymerization should restore those broken bonds, or at
least restore some bonds to the point the etching process differs
significantly. The degree of annealing effectiveness of the
original curing protocol, or other protocols created specifically
for "re-curing", require verification, if nothing else as part of
experimental control.
Despite the somewhat speculative nature on the positive side, i.e.
the notion of use of re-curing is effective as a means of annealing
out tracks from older material, the strong potential that such
annealing effects of re-curing exist seems to me sufficient to
justify controlling and evaluating for such effects when making
deductions regarding observed tracks.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
