On Jun 7, 2007, at 6:48 AM, Jed Rothwell wrote:
Michel Jullian wrote:
I suppose this would be much more likely in a contact arrangement,
they don't say if their barrier tests were done by direct contact
or with some air gap between the Pd sample and the barrier.
Other papers from BARC say there was an air gap, usually or always
-- I am not sure. This was to eliminate the possibility that water
or other chemicals caused the autoradiographs to darken. That is
extremely unlikely, but they wanted to rule it out. They also ruled
it out by placing one film behind another and observing the same
pattern of radiation on both.
Much of the work in the paper did not involve direct contact, used
separators, including the surprising electric field results. It
appears most of the work noted in the paper included spacers or filters.
BOTH TECHNIQUES USED
"For autoradiography the X-ray films were kept in contact or a few mm
away from the sample."
FIG. 1 IS A CONTACT EXPOSURE
"Fig. 1 shows a contact autoradiograph of a disk loaded with D2 using
a PF device
(30 discharge shots, 24 hours exposure)."
This almost appears to be used for control purposes.
FIG. 2 IS 0.2 mm SPACING
"Fig. 2 is an autoradiograph of a similar H2 loaded sample (30
discharge shots, 90 hours exposure) kept 0.2 mm away from the film."
ELECTIC FIELD SPACER WAS 1.2 mm THICK
"The emissions were also subjected to electric field. The electric
field between the loaded sample (disk type) and the film was
maintained by a perspex spacer, 1.2 mm thick, having an opening of 12
mm at its centre."
POLYCARBONATE FOIL SPACERS WERE 2 MICRONS
"Fogging was also detected when thin filters (2 μm aluminised
polycarbonate foil (0.25 mg/cm2) in one or several layers) were kept
between the film and loaded samples."
MEASUREMENTS WITH AND WITHOUT GLASS AND SILICA FILTERS
"The autoradiography and TLD (CaSC4 based) measurements were made
with and without
glass and fused silica filters. Activity observed without filter in
case of TLD study was seven times above background. No radiation was
observed to cross glass or fused silica, indicating the absence (or
very low intensity) of optical, ultraviolet or infrared radiators.
These results were confirmed by photomultiplier and photodiode study."
The above use of filters is not relevant regarding the spacing or
chemical isolation, but it is relevant in that it rules out any
energetic chemical or particle reactions that produce photons that
account for the fogging of the film. That pretty much leaves
production of a radioactive species that degasses from the Pd.
Regards,
Horace Heffner
