Low level gamma-spectrometry by beta coincidence

Backgrounds of gamma-ray detectors can be drastically reduced using a gas flow proportional beta counter in coincidence. The NaI(Tl) and Ge(Li) gamma-ray detectors were non-selected, usually shielded. The beta efficiencies of the samples must be high, reproducible and measurable which is the main difficulty of the method. However for small mass samples such as residues from evaporated liquids, ashes from incinerated organic samples, samples used in neutron activation analysis, the method can be used advantageously.