At 01:55 PM 11/1/2009, Michel Jullian wrote:
3/ Their tubular cell geometry inspired to me a dirt cheap Mylar
protected cell design for your kit, criticisms welcome:
- a simple plastic or glass tube, open at both ends, with its bottom
end smooth (no burrs), e.g. a test tube with its closed end cut off,
used upside down.
- wrap the Mylar film on the bottom of the tube, so that it forms a
flat horizontal window at the bottom, and the rest of the film is
folded back and taped on the tube, with all its edges reaching above
the water line to contain any electrolyte leakage
- put your detector sandwich flat under the Mylar window, and tape it
to the tube too
- install your electrodes like Oriani did (cathode rests on the bottom
Mylar window, anode above it)
Admittedly ugly, but no glue or gasket or other exotic material in
contact with the electrolyte, and think of the money you save :)
Interesting, but .... remember, I want to watch the cathode with a microscope.
I thought I'd go with the mylar, but ... I've pretty much decided
that at this point, trying to detect alphas is interesting, but not
the big game. The prize is neutrons. And it looks like, with a gold
cathode, there are plenty of them. "Plenty" may only mean something
on the order of one per minute hitting the detector, but that's fine
with CR-39 or LR-115.
I've bought the acrylic boxes used in Galileo and they seem to be the
same boxes used by SPAWAR in general. I will have the ability to
laser-cut the hole in the side to do mylar-window experiments, but I
don't see enough value to start with that. Instead, I'll do standard
wet CR-39, but with a trick: I don't really care much about the front
side, it's the back that interests me, and, since I'm looking at the
back, why not put in another piece behind it? In fact, why not line
the inside of the cell with CR-39, using commercial material? Two
pieces on each side, 250 micron material.
And then what I have is essentially a section, a slice, I can take
out of a 500 micron thick slab of CR-39, to see what activity
occurred in that. I expect to see experimental tracks that match on
both pieces of CR-39, *and those are the only ones I expect to count*
because all others are quite possibly background, accumulated in the
material since it was made. I expect to see quite clean results,
assuming that the material works at all. It's commercial makrolon,
and there is quite a bit of report on the use of that commercial
material, not everyone used the very carefully prepared Landauer (or
Tastrak) material.
It appears that I'm also being given, as an anonymous donation, a
quantity of Landauer CR-39, and I'll compare.
Stacks of CR-39 have been used before, but not in CF research, to my
knowledge. One could, in fact, place a deep stack of CR-39 outside
the cell, and characterize the neutron radiation fairly well. I can
also take two pieces of LR-115, placing them emulsion-to-emulsion,
and tape this to the outside of the cell. Again, any background would
effectively be subtracted, and what I would be counting, in the end,
would be only knock-on protons and maybe a few triple-tracks. Cool,
he? I can hardly wait. Maybe someone who is already set up will beat me to it.
Charged particle radiation was first reported by the Chinese in 1990,
using CR-39. Certainly I was impressed by the charged-particle
results from SPAWAR starting a few years ago. But the triple-track
paper knocked the ball out of the park, or knocked Park off the ball,
or something like that. Even though, in a sense, it's a "stunt,"
because it's not the primary reaction, it is, with a good technique,
so much more conclusive as to "nuclear" that it will be more
effective in changing minds. Not that that's necessarily my goal. I
don't mind if they sleep a little longer.
Once I know it's neutrons I'm looking for, why bother with mylar
windows? I could put the detectors outside the cell, but I get a
little closer to the cathode inside, so I should be able to see the
inverse-square law drop-off in proton tracks just a little bit
better. If, somehow, I could characterize the efficiency of the CR-39
in converting neutron flux to knock-on protons, it would be possible
to estimate the total neutron flux from the cathode. Assuming it is
the cathode. If it's not the cathode, that will be obvious. Heh! I
could even put CR-39 on top, why not? Inside of the lid, with holes
through it for the anode and cathode wires and temperature sensors.
Has anyone ever done this before, designed an experiment in an
extended conversation here? What happened? I know that Galileo had
extended conversations, but in a private list....
