Re: Alpha emitters

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

Daughter radionuclides of alpha emitters are certainly spread
by recoil from alpha emitting sources.  It is difficult, maybe
impossible to make an alpha emitting souce that doesn't leak
daughters due to recoil without degrading the energy spectrum.
If the daughter is not radioactive this does not apply.  Po-210
decays to stable Pb-206.  I believe the reputation Po has is
due to its chemical properties as opposed to the recoil process.

The recoil energy of the daughter can be obtained from the
non-relativistic relationship M1*T1 = M2*T2. As an example
Cm-244 decays to Pu-240 with the emission of a 5.8 MeV alpha.
The energy of the Pu-240 recoil is given by T2 = 4 * 5.8 / 240
= 0.097 MeV.  I don't have a reference in my office with stopping
powers for heavy elements in this energy range, but the range is
significant compared to acceptable covering materials for alpha
sources.

Dale E. Boyce
dale@radpro.uchicago.edu