--- On Fri, 7/3/09, William Beaty <[email protected]> wrote:
> Ludwik Kowalski used up all his 6u mylar for Oriani demo
> cells. We have a
> big spool of Kapton here at work, but no obvious way to
> measure its
> thickness. I stacked up sixteen layers, squeezed it
> with two different
> micrometers to exclude air, and repeatdly saw values of 6-7
> microns per
> layer. Also, the spool was stamped with "6" (but
> could have been "9.")
> Also, Kapton is commonly sold in thicknesses of 25u, 12.5u,
> and 6u. So it
> has to be 6u, right? 13u would be useless. It
> would be very convenient
> to have a mile-long spool of just the right material.
>
> I sent some to Ludwik, and he obtained a thickness of 13u
> by accurate
> milligram weighing. Hmmm. I quickly checked
> again and got 11u. DOH.
I'm afraid I haven't been following the discussion of Kowalski's work and don't
know why he needs the 6u material or if it has to be polyester. I use roughly
9 tons of 12.5u polyester (Mylar) film per day, so I have a lot of it around. I
also use a lot of 9u film of this type. I rarely run 6u film, but probably have
a stray roll of it and some 4u capacitor grade film as well. These rolls will
typically be 1.1m wide and 10 or 15km long. If Mr. Kowalski can't get the film
he needs elsewhere, I'll have someone search my warehouse to see if I can come
with what he needs.
I thought it was pretty funny about the measurement bias. When you have been
working with these films as long as I have, you can just sort of rub the stuff
between your fingers and identify the thickness. Virtually all of my employees
can do this, so it isn't a unique talent. Not very scientific, but apparently
more accurate than an ordinary micrometer with an unpracticed operator.
M.
