Re: Alpha emitters

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

I agree that in high specific activity Po-210 sources activity
could be sputtered by the decay of adjacent nuclei.  I was pointing
out that Po-210 was not an example of the effect in the originally
posted question.  There are many ways for contamination to escape
from an alpha source.  Radiation damage to thin films used to cover
sources can cause the films to flake off after time taking some
of the source with it.  Self sputtering of activity occurs when
sources have a high enough specific activity that a given decay has
a reasonable chance of hitting an adjacent radioactive atom.  A
monolayer of Po-210 coresponds to of the order of 1 mCi/cm^2.  Sources
with more than this specific activity will under go more sputtering.
Sources with less than this activity wil rapidly decrease in the
amount of sputtering that occurs.

Dale