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Re: Natural U check source

At 14:32 07.03.97 -0600, you wrote:
>Does anyone know of a good source (no pun intended) for a natural U check
>to be used for calibrating instruments for detecting alpha particles on
>We have an Eberline SPA-1A and need a calibration source before doing some 
>swipe tests for loose alpha contamination.  The source should be no larger
>25 mm diameter by 1.5 mm in thickness.  Active area should be 16 mm in
>or larger.  We want to use natural U since that is what we will be looking for 
>in the actual situation.

In the good old days we prepared the K-40 sources for "gross beta counting"
by spraying KCl on planchets.

Even for uranium sources I would recommend to prepare them yourself by
applying natural uranium salts in the geometry you need. Make sure to find a
source of uranium with natural isotopic composition and not being depleted.
On the other side I wonder how you perform swipe tests, so that you need a
disk with 1.5 mm thickness. I cannot imagine that any swipe will show such a
geometry. Therefore we have since long done swipe tests on beta and alpha
emitters by liquid scintillation spectrometry, where we do not have the
problem of geometry. LSC always gives us a 4 pi geometry, even for the
emitter of the lowest beta energies.


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