Development of a high-efficiency 4πβ(LS)-γ coincidence system for direct measurements of activity in radioactive decay

We developed a new 4πβ(LS)-γ coincidence counting system to be used for radionuclide standardization. The liquid scintillation detector used in this system enables the easy preparation of sources without self-absorption. A special beta-beta coincidence technique is implemented to suppress large thermal and electronic noises, resulting in a higher coincidence efficiency and reduced uncertainty in the measurements of low-energy beta-emitting radionuclides. The system is commissioned with the activity measurement of ⁶⁰Co. The measured activity is derived with 90% efficiency for the beta ray detection.