A simple, powerful 4 pi/beta/gamma coincidence system based on the pulse-mixing method

An improved version of a simple and powerful 4 pi beta/gamma coincidence sy stem based on the pulse-mixing method is described. It is based on the use of extendable dead-limes measured by the live-time technique. The coinciden ce channel is replaced by a "virtual" common channel where pulses coming fr om both beta and gamma detectors are mixed and counted together. The basic property of this common channel is to register no more than one pulse per c oincident pair of pulses. A single channel-analyzer or an analog-to-digital converter (ADC) can be incorporated in the gamma channel. If an ADC is use d, coincident and non-coincident spectra can be deduced from the recording. All the major problems (dead-time, accidental coincidences corrections) en countered in conventional systems are eliminated. An important feature of t his system is its insensitivity to the delay between beta and gamma pulses. This coincidence method has been tested successfully for several radionucl ides (Co-60, Cs-134, Sr-85 and Yb-169) presenting different measurement dif ficulties, including metastable states (Sr-85 and Yb-169). It is now used r outinely for activity measurements. (C) 1999 Elsevier Science B.V. All righ ts reserved.