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Re: "flighty" Plutonium

At 05:23 PM 4/21/98 -0500, you wrote:
>I have personally observed a 50k dpm (alpha)  particle "disappearing", 
>while waiting for someone to bring me a piece of tape.  Kinda like a flea.

Something to consider: if the 50k dpm quantity is what you can detect with
an alpha-sensitive instrument, the actual activity of the particle will be
higher, and potentially much, much higher, with only a fraction of the
alphas escaping the source particle and thus being detectable. The
radiation from the remainder of the activity, which can be well over 90
percent of the total activity, is absorbed within the particle itself, and
generate a huge electrostatic charge, resulting in the "flea" phenomenon.

However, if the 50k dpm is an assessment of total activity in the source,
self-absorption  is unlikely to be large enough to explain the sudden
particle jump.

Bob Flood
Dosimetry Group Leader
Stanford Linear Accelerator Center
(650) 926-3793