Practical+Exercise+for++Liquid+Scintillation

Back to main The students are first divided into two groups. Each group follow the procedures described below.

Laboratory Procedure
Determination of the counting efficiency of 3 H and 14 C a) Prepare one standard sample (unquenched) for each of the two radionuclides 3 H and 14 C in two separate liquid scintillation vials. This is done by extracting an aliquote of 1.00 mL from the respective mother solution into the two vials. Add 10 mL scintillation cocktail to each vial and shake to a homogeneous solution. b) Count the standard samples on the Beckman LS counter in the MCA mode. Define channel 1 as the counting window covering the 3 H spectrum, and channel 2 as that part of the 14 C spectrum which does not overlap with the 3 H spectrum. For 14 C record the counting rate in both channels. c) Determine the counting efficiency ε CH1 ( 3 H), ε cH1 ( 14 C), ε CH2 ( 14 C) and ε CH1 + CH2 ( 14 C) from eqn 2 in Interfering Processes d) Record (plot) the scintillation spectra for the two radionuclides.

Reporting Schemes and results
Suggested appearance
 * ~ Table 1: Background Counting ||
 * Number of counts S b ||  ||
 * Counting time (min) ||  ||
 * counting rate R b (cpm) ||  ||


 * ~ Table 2 Discriminator Settings ||
 * || CH1 || CH1 ||
 * Upper limit (keV) ||  ||   ||
 * Lower limit (keV) ||  ||   ||

(background-corrected cpm) ||  ||   || (background-corrected cpm) ||  ||   || (dpm) ||  ||   || On the spectra plots indicate upper and lower limit for CH1 and CH2.
 * ~ Table 3: Determination of the Counting Efficiency of 3 H and 14 C ||
 * Description || 3 H || 14 C ||
 * Applied Counting Program ||  ||   ||
 * Counting rate CH1: RCH1
 * Counting rate CH2: RCH2
 * Disintegration rate standard
 * Counting efficiency CH1: ε CH1 ||  ||   ||
 * Counting efficiency CH2: ε CH2 ||  ||   ||
 * Total counting efficiency in CH1+CH2: ε CH1 + CH2 ||  ||   ||