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The following items describes practical aspects of LSC from different metrology
labs.
PTB experience :
Sample composition :
We use 15 ml Ultima Gold (bottle opened not more than 3 months before) and 0,5 or 1 ml
of water to be sure on the concentration of water micelles, or, in case of elements only stable in a very acidic solutions
(e.g. Pa-233, the daughter of Np-237), 15 ml of Ultima Gold AB with 1 ml of 6 m HCl.
As a quenching agent we use nitromethane and not CHCl3 or CCl4. The reason is the high Z of Cl.
Counting technique :
Open channel. In case of beta emitters with a high energy (e.g. P-32, Y-90, Sr-89) we found count rates which are too low.
Therefore in such cases we use quenched samples.
It may be a specific effect of the Wallac 1414 counter. (Experience from anybody ?)
Quality check :
We repeat the countings over a long time and look for changes in the results. Grau Carles had reported changes in the spectra,
but we don't use this for a check.
LSC vials
Using translucent vial surface improves detection efficiency
and spectrum resolution
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