Leigh: You brought up a good point about the possibility that
Polonium-208 might have been used instead of Polonium-210 in
radioactive spark plugs. The problem I have is that for any
applications such as spark gaps or ionizers, it is Po-210 that
is used. Also, as I mentioned in my original posting, I can
easily measure a Radium-226 gamma spectrum, although that could
possibly be a trace contaminant in a source of Thorium.
The other problem I have is that why is Po-210 provided by
makers of radioactive sources, instead of Po-208, if that would
be easy to obtain? Is it because that the 138 day half-life
of Po-210 requires more frequent replacing than would the
2.9 year half-life Po-208, as a source of alphas?
In looking at the Table of Isotopes, I see that Po-210 decays
almost 100% by alpha emission to the ground state of Lead-206,
but there is a 0.001% branch to the first excited state which
would then emit a gamma ray of about 800 keV. However, Po-208
decays most of the time by alpha emission to the ground state
of Lead-204, but there is a 0.006% branch by electron capture
to Bismuth-208, leading to emission of about 300 keV and 600
keV gamma rays, of equal intensities. Is the higher background
of gammas from a Po-208 alpha source then the reason that
Po-210 is used for alphas, or is it because the 210 is easier
to make?
Finally, exactly how is Po-210 manufactured as a source??
Tom Walkiewicz walkiewicz@edinboro.edu
Dept. Physics 814-732-2468
Edinboro University
Edinboro, PA 16444