A simple, powerful 4π/β/γ coincidence system based on the pulse-mixing method

An improved version of a simple and powerful 4 pi beta/gamma coincidence system 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 coincidence channel is replaced by a "virtual" common channel where pulses coming from 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 coincident 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 used, coincident and non-coincident spectra can be deduced from the recording. 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. This coincidence method has been tested successfully for several radionuclides (Co-60, Cs-134, Sr-85 and Yb-169) presenting different measurement difficulties, including metastable states (Sr-85 and Yb-169). It is now used routinely for activity measurements. (C) 1999 Elsevier Science B.V. All rights reserved.