[NewCandle] influence of aluminum geometry on Geiger counter rates

[Nick Reiter]

Hi Jones,

> That would be interesting if the dimensions between the
> layers were in the
> range of nanometers, but that small gap on average would be
> unlikely unless
> they rolled very tightly. Do you think the spacing could be
> 10 nm or less in
> a large proportion of the rolls?

**********Down at that size scale its probably almost random within a range, depending on surface roughness and tensile stress.  I burned out some brain cells on a search for some meaningful data.  If two turns of foil, under what probably is compressive force, have a surface roughness of Ra=X, then the curved planar gap between turns would be anything from the thickness of the native oxide layer to 2X I suppose.  There would probably be lots of channels and caverns, the majority of which would be aligned normal to the long axis of the roll, due to the original stainless extruding rolls (and their finish).  I saw figures stating the Ra of the rough side of the foil varied between 50nm and 500nm.  So I suspect some regions of the roll would have more "force" than others.

> It would be 'way cool' to find that the Casimir attraction
> force, which is a
> negative or exclusionary force, actually could diminish
> gamma radiation,
> which is a much shorter wavelength than the gap. 

**************You know, outside of making a many-layered vacuum deposited thin film structure with say Al and SiO2 or Al and MgF, large mass Al foil would be about as close as one is going to get to approximating that which Al Schwartz used to rant about - Casimatter.  Especially if the voids between turns were filled with a thin layer of a UV transparent liquid medium.  Lawdy, a whole range of experiments comes to mind, looking for inertial anomalies, etc. all using foil rolls.


> 
> This could also lead to a marketable discovery - i.e.
> reactor shielding made
> in tightly wound rolls ;-) ... think *nuclear powered
> aircraft* and reducing
> the weight of shielding by enough to make it feasible.

**********The definitive test for this would be quite simple, and I suspect before I open my mouth too much more on the topic, I should try it.  A sealed glass tube containing some Th or U would be inserted into a "dummy" pipe of aluminum, bored and sized to be equitable in mass with a foil roll, but be a simple thick wall solid.  A Geiger counter window is positioned outside of the pipe at a constant distance.

This is then compared with readings made by the same emitter inserted into a foil roll.  Finally, water or a solution is allowed to penetrate into the roll, and we see if any change results.

Jones is right - the gap between foil turns in most spots is probably not tight enough to match vacuum mode with gamma wavelength.  But maybe here and there, on the roll, in small areas, it is.

N

> 
> BTW - if Terry is tuned in: The "Georgia Nuclear Aircraft
> Laboratory" was a
> secret USAF Lab operated by Lockheed and located near
> Dawsonville, Ga. It
> was mentioned in a pretty decent account of the failings of
> the US nuclear
> program which I read recently - written by a Ga Tech grad,
> whose name slips
> my memory at the moment. 
> 
> ... otherwise I would recommend it :) Blame another
> Georgian - Jimmy Carter
> - for most of that failure.
> 
> Jones
> 
> 
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