On Aug 2, 2007, at 3:05 AM, Michel Jullian wrote:
Horace,
It occurred to me that to fabricate the thin film cathode we could
use the dielectric material's parasitic conductivity, or possibly
some capacitive method (using pulsed DC?), to deposit the PdD thin
film directly onto the material. Incidentally, this could well be
what actually happens on the clear plastic walls of the HV
submitted SPAWAR cells, without anyone ever noticing because the
deposit is so thin that it is transparent :-)
An interesting hypothesis. It would only account for some excess
heat though. It would not account for the cathode morphology
changes, the cathode hot spots, or the particle emission from the
cathodes. The HV electrodes are not against the CR-39 in the Szpak
cells, but out against the plastic container walls, as you know, so
there should be no particles detected from them.
The cathode fabrication process, and preparation for subsequent
normal operation, could go like this:
1/ Fill the cell container e.g. a test tube made of the right
dielectric material (e.g. a clear plastic e.g. polycarbonate...
e.g. CR-39 !) with the electrolyte we will be using for normal
operation (that for PdD codeposition)
2/ Immerse the test tube into a thick walled glass container filled
with salt water, aligning the levels.
3/ Immerse a grounded wire into the salt water (this connects the
outside of the tube to ground)
4/ Immerse an anode wire or rod (the same we will be using for
normal operation) axially into the electrolyte and connect it to a
+HV wire ( the same we will be connecting later to the salt water,
e.g. the +25kV wire of an old CRT). A low current will thus start
leaking from +HV to ground through the electrolyte and through the
dielectric tube walls, from the inside to the outside, and thus the
desired PdD codeposition will occur on the inside wall of the tube.
5/ Wait for the deposit to grow to the desired thickness (monitor
the total charge circulated by the HV supply to determine the
deposited amount using Faraday's law of electrolysis)
6/ Then establish the connections for normal operation: connect the
deposited thin film cathode to ground, the anode to a positive low
voltage suitable for normal operation electrolysis, and the salt
water to the +HV wire to capacitively establish the desired high
electron density on the back side of the cathode as we have discussed.
Hope this makes sense.
Sure does make sense, and it is an nifty approach to building a co-
deposited cathode on CR-39. I gave a thought to direct co-deposition
on BaTO3 when I saw it is moderately conductive at high voltages, and
its conductivity is controllable through additives:
http://www.avxcorp.com/docs/techinfo/mlcmat.pdf
I still think gas phase is the way to go to make progress toward
practical use. I'm convinced a gas phase back side is important to
(1) preserve the high field at the surface and immediate subsurface
of the HV back side of the cathode and (2) provide some prospect of a
non-destructive process which can also remove the helium ash, which
is very destructive to the lattice and comparatively immobile.
It would be terrific if hydrogen loading could be done or at least
maintained in gas phase by high voltage. In that case there is no
need for a "back side" at all. Claytor accomplished this using thin
wires, so that indicates it should be feasible to do for large
surface cathodes. Claytor had the topological advantage of the high
field gradient the thin wires achieve. A simple place to start might
be co-deposition on Pd wires prior to use in gas mode. CR-39
detectors can be placed directly against the wire(s), or the wire(s)
wrapped around them.
If fusion on or immediately above the surface can be sustained
without destruction of the cathode then that is a home run. Even if
it can be only sustained by a process that ablates the top layer and
thus is not self-quenching then that too is a home run.
From a practical standpoint, if surface fusion can not be sustained,
it might be nifty to use the gas equivalent of a fluidized bed. That
would consist of pre-manufacturing co-deposited particles in powder
form and placing them on a conductive substrate, for experimental
purposes possibly CR-39, or CR-39 with a thin film gold film
deposited on top. The anode would be located above the bed. In this
way cathode film separation would not become a problem and the active
material and active sites could be changed by vibrating the powder
and periodically replacing the powder.
Horace Heffner
http://www.mtaonline.net/~hheffner/
