[Gorzaloon]

If it is the Po they have found it is of course an alfa-emitter, and then they must have measured very close to the source

There is a Gamma associated with that alpha decay. About 4-500 KeV. One can detect the gamma from a thorium 232 decay in an old Coleman lantern mantle from a foot away or more.

232Th has a lower specific activity than 210Th.

[ScaniaBoy]

Thanks for the info re the decay.