A simple, powerful 4 pi beta/gamma coincidence system

A simple and powerful 4 pi beta/gamma coincidence system which uses extendible dead-times and a common channel instead of a coincidence channel is described. All the major problems (dead-time, accidental coincidences corrections) encountered in conventional systems are eliminated. An important feature of this system is its insensitivity to the delay between beta and gamma pulses. The activity measurement of a radionuclide having a delayed state such as Sr-85 (1 mu s) becomes then very simple. An analog-to-digital converter (ADC) incorporated in one channel allows the recording of a complete spectrum. This instrument has been tested by the measurement of Co-60 sources previously measured by another system. The result of the activity determination of a Sr-85 solution is also presented.