A 4 πβ− γ coincidence system with minimally broadened pulses

Abstract

The performance characteristics of a new type 4 π β− γ coincidence system have been measured. In contrast with the conventional 4 π β− γ circuitry, which is based on a fixed pulse width (∼2 μs) and a non-extendable dead time, the pulse processing circuitry in this new system is based on a minimally broadened pulse (i.e., as narrow as 0.25 μs). In this system each pulse has a different pulse width, so that the dead times for the β- and γ-ray detectors are determined by summing the measured dead time attributed by each pulse in each channel. The β− γ coincidences are defined with an overlap coincidence circuit. This system is shown to be much less sensitive to mismatch in the coincidence timing than is the conventional system. In spite of the narrower pulse widths, no spurious β pulses are observed when the 4π proportional counter is operated near the center of its plateau. Disintegration rates were measured for calibrated sources with strength up to ∼ 10 6 Bq. These data indicate that with this new system the disintegration rates of very intense sources (∼ 10 6 Bq) and moderately intense sources (<10 5Bq) can be determined with accuracies of ∼4% and ⩽0.1%, respectively.