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Re: CR-39



I just realized this method is similar, but reversed, to an earlier (the
earliest?) photo' method. It's a resist method in which a metallic
plate is coated w/ bitumen exposed (very long exposure!) and developed
by removing w/ a solvent. I presume the light promotes polymerization;
the polymerized bitumen being less soluble.

bc, who wonders if bitumen could be used to detect Alphas, being
sufficiently insensitive to light or the SS industry's resist.

Ludwik Kowalski wrote:

I found a domestic supplier of CR-39. The
minimum order is $100 for 100 pieces of
1 cm^2 each. These pieces are good for
student projects involving contamination
of air, soil or water with alpha radioactive
substances, such as radon in air, plutonium
in soil or water, etc. I will be happy to help
you, if my help is still needed after reading
what is described in the Internet.

The supplier is Craig Gabler at:
AlphaTrak Learning
141 Northridge Drive
Centralia, WA 98531

You can contact him by e-mail at:

radon@alphatrak.com

He used to be a science teacher but providing
CR-39 to schools is now his business.
Look at his web site:

http://www.fbr.org/swksweb/radon.html

Also look at the web site in England

<http://home.clara.net/camplin/TNotes/Conts.htm>

Ordering from England from the US has
a minimum of $500, which is too high.
One of my students is now investigating
a possibility of using Lexan, which is at
least 1000 times less expensive, instead
of CR-39. She is using the Am-241 from a
smoke alarm as a source of alpha particles.
Tracks are nicer in CR-39 than in Lexan
but Lexan is OK, especially when a dye
(which biologists use to stain bacteria)
is used by her. Another project has to do
with soil in eastern Slovakia, not too far
from Chernoble.

Alpha particles penetrating some plastic
materials create latent tracks which can
be made visible by etching. Tracks can
then be observed (or counted) under an
optical microscope. We find the objective
10X very convenient for counting (with
the standard M=10 eyepiece).
Ludwik Kowalski