Re: need a simple way to detect charge of radioactive particle other than electroscope


"Guy Macon" <http://www.guymacon.com/> wrote in message
news:11e95nmkug15cef@xxxxxxxxxxxxxxxxxxxxx
>
>
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> Jon Hightower wrote:
>
> >The subject of this thread says it all. I am teaching a summer class
within
> >the next week and I need to show the class a way to determine the charge
> >emitted from a radioactive substance so they can infer the type of
radiation
> >emitted (alpha, beta or gamma). I have tried using an electroscope,
which
> >would have been ideal, but I cannot get the unit to function. Therefore,
I
> >can't depend on this as a detector during class. Remember that I am
seeking
> >to determine charge only, not just detection in general which a Geiger
> >counter would do. And, yes, part 2 of the lesson will involve using
> >shielding of various thicknesses to conclude what type of particle is
> >emitted.
> >
> >Any ideas for a charge polarity detector other than an oscilloscope-
> >something that's cheap?
>
> May I assume that your use of the word "oscilloscope" is a result of
> your spellchecker mangling the word "electroscope?"

Yes, sorry about that. I feel pretty dumb for letting that slip in there
:(.


> Instead of giving up, you should figure out why it is that you
> cannot get an electroscope to function when electroscopes have been
> working fine for everyone else for the last 250 years. Could you
> descibe your electroscope and radiation source, what you expected
> to happen and what actually happened? I will be glad to help you
> figure out what went wrong.

Today, I built the electroscope you linked to here:
http://www.geocities.com/CapeCanaveral/Hall/1805/electroscope.html
Unfortunately, still no results. I tried the comb test as described and
nothing. Basically, for part of my lesson, I just want to show that alpha
and beta radiation has charge as I'm no longer concerned with trying to
determine polarity. The sources I have are small, plastic embedded discs of
1 uC beta and gamma emitters. I lack an alpha source, but I am thinking of
using Am 241 from a smoke detector. I have tried bringing the beta source
up to the top of the electroscope, but no result. As I can't get the
electroscope to work anyway, I don't know if the reason is due to too weak
of a source or just a fault in the electroscope itself.

My other option, also presented in this thread, is to try using a sensitive
FET transistor circuit to detect charge:
http://amasci.com/emotor/chargdet.html#2 (scroll to the top of the page)
This circuit has the advantage of simplicity and might actually detect the
small charge from the apha/ beta sources. Perhaps polarity also as if
negative, maybe the bulb would dim (?). Of course, I don't know, but if
there's any chance this could work, it would be a great substitute for the
electroscope. Thoughts?

Jon
> Look here:
> http://pbskids.org/zoom/activities/sci/electroscope.html
> http://www.nfinity.com/~exile/electro.htm
> http://www.geocities.com/CapeCanaveral/Hall/1805/electroscope.html
> http://www.hep.princeton.edu/~mcdonald/examples/ph104_2004/ph104_exp01.pdf
>
> If you are bound and determined to use another method, here is one:
> http://www.amasci.com/emotor/chargdet.html
> ...but you will have an easier time getting an electroscope to work.
>
> --
> Guy Macon <http://www.guymacon.com/>
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