Halflife source ?

[CEPPERSON@life.uams.edu]

Someone recently mentioned how to make a one-hour halflife 
source using a thorium-coated mantle and a nickle coin.
The reference quoted was The Physics Teacher, 30, 1992, p.16.
That reference turns out to be *RADIOACTIVEBALL* and deals
with natural radon. Can anyone supply the correct reference
for making the thorium-nickle source?

Thanks in advance for any help.

Claude Epperson

cepperson@life.uams.edu
University of Arkansas for Medical Sciences
Little Rock, AR