What is beta counter?

Answer 1

In the beta-counter or liquid scintillation counter, the sample is dissolved in an organic scintillation solution. Due to the resulting 100% counting geometry and the absence of any detector window, this means that the counter has excellent properties in detecting radionuclides of low activity emitting low energy beta-particles, such as H3 and C14. The light photons from the sample are collected by two photomultipliers in coincidence. This arrangement will reduce the background due to thermal noise and only true scintillation events will be analysed and counted. The main problem in liquid scintillation counting is the varying counting efficiency due to quenching of scintillation events. This process is caused by chemical contamination of the sample and/or a coloured sample. This means that the counting efficiency has to be determined for every sample. Therefore a quality control of the instrument must include a control of the correction methods. Otherwise the QC methods will be the same as for any scintillation counter.

The sources needed for QC of a liquid scintillation counter include calibrated sources of H3 and C14 with different counting efficiencies as well as a background sample.