> Thanks for the replies - I think I figured it out. When I put the
> probe about 2 cm away, I get about 2000 CPM. At this distance,
> inserting paper makes no difference and inserting copper sheet makes a
> small difference. However, if I put the probe about 8mm away, I get
> more than 30000 CPM and at this distance, inserting a single sheet of
> paper cuts the count way down. I think I was seeing gamma at 2 cm away
> and at <1cm, I am seeing the alpha as well.

You don't think that the Beta will also feature ?

Beta 0.052 MeV  ... able to penetrate through several feet of air, or
several millimeters of plastic

Gamma 0.033 MeV  ...  Depending on their energy, they can be stopped by a t=
hin
 piece of aluminum foil or ... penetrate inches of lead.(not in your case :=
-) ).


Your description of what you observe doesn't seem to exclude Beta
playing a part.
Adding an electric field would help to test this. Just maybe you could
modulate the field and look for corresponding GM output modulation for
Beta but not Gamma.


            Russell
--=20
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