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LSC (Delay before burst)
Please delete if you are not interested in liquid scintillation counting.
Dear all,
Can somebody please explain the following:
Two tritium sources are counted in a Tri Carb 2700 TR. The first source contains approximately 8 kBq of tritium while the other source contains approximately 600 Bq of tritium. The quench levels are identical and the cocktail used is Ultima Gold AB. The high sensitivity count mode is not used.
However, when the "Delay Before Burst" setting (which may be used to optimise the background reduction) is changed from "normal" (75 ns) to 800 ns, the ratio between the count rates of the two sources decreases significantly, indicating that under "normal" circumstances relatively more events are counted for the higher activity (i.e., the counting efficiency is a function of the tritium activity).
We were able to deal with this occurence as all settings are checked before use. However, if default settings are used, this effect may go unnoticed.
Regards,
Arvic Harms
Dr Arvic Harms
Division Quality of Life
National Physical Laboratory
Queens Road
Teddington TW11 0LW
Middlesex
United Kingdom
E-mail: arvic.harms@npl.co.uk
Tel ++44 20 8943 8512
Fax ++44 20 8614 0488
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